WorldWideScience

Sample records for amyloplasts

  1. Cytoskeleton-amyloplast interactions in sweet clover

    Science.gov (United States)

    Guikema, J. A.; Hilaire, E.; Odom, W. R.; Spooner, B. S. (Principal Investigator)

    1993-01-01

    The distribution of organelles within columella cells of sweet clover was examined by transmission electron microscopy following growth under static or clinorotating conditions. A developmentally conditioned polarity was observed, with a proximal location of the nucleus and a distal accumulation of the endoplasmic reticulum. This polarity was insensitive to clinorotation. In contrast, clinorotation altered the location of amyloplasts. Application of cytoskeletal poisons (colchicine, cytochalasin D, taxol, and phalloidin), especially during clinorotation, had interesting effects on the maintenance of columella cell polarity, with a profound effect on the extent, location, and structure of the endoplasmic reticulum. The site of cytoskeletal interactions with sedimenting amyloplasts is thought to be the amyloplast envelope. An envelope fraction, having over 17 polypeptides, was isolated using immobilized antibody technology, and will provide a means of assessing the role of specific peptides in cytoskeleton/amyloplast interactions.

  2. Pea amyloplast DNA is qualitatively similar to pea chloroplast DNA

    Science.gov (United States)

    Gaynor, J. J.

    1984-01-01

    Amyloplast DNA (apDNA), when subjected to digestion with restriction endonucleases, yields patterns nearly identical to that of DNA from mature pea chloroplasts (ctDNA). Southern transfers of apDNA and ctDNA, probed with the large subunit (LS) gene of ribulose-1,5-bisphosphate carboxylase (Rubisco), shows hybridization to the expected restriction fragments for both apDNA and ctDNA. However, Northern transfers of total RNA from chloroplasts and amyloplasts, probed again with the LS gene of Rubisco, shows that no detectable LS meggage is found in amyloplasts although LS expression in mature chloroplasts is high. Likewise, two dimensional polyacrylamide gel electrophoresis of etiolated gravisensitive pea tissue shows that both large and small subunits of Rubisco are conspicuously absent; however, in greening tissue these two constitute the major soluble proteins. These findings suggest that although the informational content of these two organelle types is equivalent, gene expression is quite different and is presumably under nuclear control.

  3. Major Proteins of the Amyloplast of Agar and Soil - Grown Potato Tubers

    DEFF Research Database (Denmark)

    Hald, Simon; Blennow, Andreas; Stensballe, Allan

    and total tuber extracts by SDS-PAGE and the specific activities of marker enzymes for amyloplast, cytosol, mitochondria and the vacuole. SDS-PAGE separated amyloplast and starch granule proteins were in-gel digested with trypsin, analyzed by mass spectrometry, and identified by searches against presently...

  4. Proteomic characterization of wheat amyloplasts using identification of proteins by tandem mass spectrometry.

    Science.gov (United States)

    Andon, Nancy L; Hollingworth, Sarah; Koller, Antonius; Greenland, Andrew J; Yates, John R; Haynes, Paul A

    2002-09-01

    We describe the initial characterization of the wheat amyloplast proteome, consisting of the identification and classification of 171 proteins. Whole amyloplasts and purified amyloplast membranes were prepared from wheat (Triticum aestivum). Protein extracts were examined by one-dimensional and two-dimensional electrophoresis, followed by high performance liquid chromatography-tandem mass spectrometry of separated proteins. Tandem mass spectrometry data of individual peptides was then searched by SEQUEST, using a database containing known protein sequences from both wheat and other homologous cereal crops. Using this approach we identified 108 proteins from whole amyloplasts and 63 proteins from purified amyloplast membranes. The majority of protein identifications were derived from protein sequences from cereal crops other than wheat, for which relatively little gene sequence data is available. The highest percentage of protein identifications obtained from any individual species was 46% of the total number of proteins identified, using sequence data found in our proprietary rice (Oryza sativa) genome database.

  5. The influence of gravity on the formation of amyloplasts in columella cells of Zea mays L

    Science.gov (United States)

    Moore, R.; Fondren, W. M.; Koon, E. C.; Wang, C. L.

    1986-01-01

    Columella (i.e., putative graviperceptive) cells of Zea mays seedlings grown in the microgravity of outer space allocate significantly less volume to putative statoliths (amyloplasts) than do columella cells of Earth-grown seedlings. Amyloplasts of flight-grown seedlings are significantly smaller than those of ground controls, as is the average volume of individual starch grains. Similarly, the relative volume of starch in amyloplasts in columella cells of flight-grown seedlings is significantly less than that of Earth-grown seedlings. Microgravity does not significantly alter the volume of columella cells, the average number of amyloplasts per columella cell, or the number of starch grains per amyloplast. These results are discussed relative to the influence of gravity on cellular and organellar structure.

  6. Roles of amyloplasts and water deficit in root tropisms.

    Science.gov (United States)

    Ponce, Georgina; Rasgado, Fátima A; Cassab, Gladys I

    2008-02-01

    Directed growth of roots in relation to a moisture gradient is called hydrotropism. The no hydrotropic response (nhr1) mutant of Arabidopsis lacks a hydrotropic response, and shows a stronger gravitropic response than that of wild type (wt) in a medium with an osmotic gradient. Local application of abscisic acid (ABA) to seeds or root tips of nhr1 increased root downward growth, indicating the critical role of ABA in tropisms. Wt roots germinated and treated with ABA in this system were strongly gravitropic, even though they had almost no starch amyloplasts in the root-cap columella cells. Hydrotropically stimulated nhr1 roots, with or without ABA, maintained starch in the amyloplasts, as opposed to those of wt. Hence, the near-absence (wt) or abundant presence (nhr1) of starch granules does not influence the extent of downward gravitropism of the roots in an osmotic gradient medium. Starch degradation in the wt might help the root sustain osmotic stress and carry out hydrotropism, instead of reducing gravity responsiveness. nhr1 roots might be hydrotropically inactive because they maintain this starch reserve in the columella cells, sustaining both their turgor and growth, and in effect minimizing the need for hydrotropism and at least partially disabling its mechanism. We conclude that ABA and water stress are critical regulators of root tropic responses.

  7. Metabolic pathways of the wheat (Triticum aestivum endosperm amyloplast revealed by proteomics

    Directory of Open Access Journals (Sweden)

    Dupont Frances M

    2008-04-01

    Full Text Available Abstract Background By definition, amyloplasts are plastids specialized for starch production. However, a proteomic study of amyloplasts isolated from wheat (Triticum aestivum Butte 86 endosperm at 10 days after anthesis (DPA detected enzymes from many other metabolic and biosynthetic pathways. To better understand the role of amyloplasts in food production, the data from that study were evaluated in detail and an amyloplast metabolic map was outlined. Results Analysis of 288 proteins detected in an amyloplast preparation predicted that 178 were amyloplast proteins. Criteria included homology with known plastid proteins, prediction of a plastid transit peptide for the wheat gene product or a close homolog, known plastid location of the pathway, and predicted plastid location for other members of the same pathway. Of these, 135 enzymes were arranged into 18 pathways for carbohydrate, lipid, amino acid, nucleic acid and other biosynthetic processes that are critical for grain-fill. Functions of the other proteins are also discussed. Conclusion The pathways outlined in this paper suggest that amyloplasts play a central role in endosperm metabolism. The interacting effects of genetics and environment on starch and protein production may be mediated in part by regulatory mechanisms within this organelle.

  8. Variation in stem morphology and movement of amyloplasts in white spruce grown in the weightless environment of the International Space Station

    Science.gov (United States)

    Rioux, Danny; Lagacé, Marie; Cohen, Luchino Y.; Beaulieu, Jean

    2015-01-01

    One-year-old white spruce (Picea glauca) seedlings were studied in microgravity conditions in the International Space Station (ISS) and compared with seedlings grown on Earth. Leaf growth was clearly stimulated in space whereas data suggest a similar trend for the shoots. Needles on the current shoots of ground-based seedlings were more inclined towards the stem base than those of seedlings grown in the ISS. Amyloplasts sedimented in specialized cells of shoots and roots in seedlings grown on Earth while they were distributed at random in similar cells of seedlings tested in the ISS. In shoots, such amyloplasts were found in starch sheath cells located between leaf traces and cortical cells whereas in roots they were constituents of columella cells of the cap. Nuclei were regularly observed just above the sedimented amyloplasts in both organs. It was also frequent to detect vacuoles with phenolic compounds and endoplasmic reticulum (ER) close to the sedimented amyloplasts. The ER was mainly observed just under these amyloplasts. Thus, when amyloplasts sediment, the pressure exerted on the ER, the organelle that can for instance secrete proteins destined for the plasma membrane, might influence their functioning and play a role in signaling pathways involved in gravity-sensing white spruce cells.

  9. Isolation of cDNA encoding a newly identified major allergenic protein of rye-grass pollen: intracellular targeting to the amyloplast.

    OpenAIRE

    Singh, M B; Hough, T; Theerakulpisut, P; Avjioglu, A; Davies, S; Smith, P M; Taylor, P; Simpson, R J; Ward, L D; McCluskey, J

    1991-01-01

    We have identified a major allergenic protein from rye-grass pollen, tentatively designated Lol pIb of 31kDa and with pI 9.0. A cDNA clone encoding Lol pIb has been isolated, sequenced, and characterized. Lol pIb is located mainly in the starch granules. This is a distinct allergen from Lol pI, which is located in the cytosol. Lol pIb is synthesized in pollen as a pre-allergen with a transit peptide targeting the allergen to amyloplasts. Epitope mapping of the fusion protein localized the IgE...

  10. Overriding the co-limiting import of carbon and energy into tuber amyloplasts increases the starch content and yield of transgenic potato plants.

    Science.gov (United States)

    Zhang, Lizhi; Häusler, Rainer E; Greiten, Christian; Hajirezaei, Mohammad-Reza; Haferkamp, Ilka; Neuhaus, H Ekkehard; Flügge, Ulf-Ingo; Ludewig, Frank

    2008-06-01

    Transgenic potato (Solanum tuberosum) plants simultaneously over-expressing a pea (Pisum sativum) glucose-6-phosphate/phosphate translocator (GPT) and an Arabidopsis thaliana adenylate translocator (NTT1) in tubers were generated. Double transformants exhibited an enhanced tuber yield of up to 19%, concomitant with an additional increased starch content of up to 28%, compared with control plants. The total starch content produced in tubers per plant was calculated to be increased by up to 44% in double transformants relative to the wild-type. Single over-expression of either gene had no effect on tuber starch content or tuber yield, suggesting that starch formation within amyloplasts is co-limited by the import of energy and the supply of carbon skeletons. As total adenosine diphosphate-glucose pyrophosphorylase and starch synthase activities remained unchanged in double transformants relative to the wild-type, they cannot account for the increased starch content found in tubers of double transformants. Rather, an optimized supply of amyloplasts with adenosine triphosphate and glucose-6-phosphate seems to favour increased starch synthesis, resulting in plants with increased starch content and yield of tubers.

  11. Isolation of cDNA encoding a newly identified major allergenic protein of rye-grass pollen: intracellular targeting to the amyloplast.

    Science.gov (United States)

    Singh, M B; Hough, T; Theerakulpisut, P; Avjioglu, A; Davies, S; Smith, P M; Taylor, P; Simpson, R J; Ward, L D; McCluskey, J

    1991-01-01

    We have identified a major allergenic protein from rye-grass pollen, tentatively designated Lol pIb of 31kDa and with pI 9.0. A cDNA clone encoding Lol pIb has been isolated, sequenced, and characterized. Lol pIb is located mainly in the starch granules. This is a distinct allergen from Lol pI, which is located in the cytosol. Lol pIb is synthesized in pollen as a pre-allergen with a transit peptide targeting the allergen to amyloplasts. Epitope mapping of the fusion protein localized the IgE binding determinant in the C-terminal domain. Images PMID:1671715

  12. Amyloplast sedimentation dynamics in maize columella cells support a new model for the gravity-sensing apparatus of roots

    Science.gov (United States)

    Yoder, T. L.; Zheng, H. Q.; Todd, P.; Staehelin, L. A.

    2001-01-01

    Quantitative analysis of statolith sedimentation behavior was accomplished using videomicroscopy of living columella cells of corn (Zea mays) roots, which displayed no systematic cytoplasmic streaming. Following 90 degrees rotation of the root, the statoliths moved downward along the distal wall and then spread out along the bottom with an average velocity of 1.7 microm min(-1). When statolith trajectories traversed the complete width or length of the cell, they initially moved horizontally toward channel-initiation sites and then moved vertically through the channels to the lower side of the reoriented cell where they again dispersed. These statoliths exhibited a significantly lower average velocity than those sedimenting on distal-to-side trajectories. In addition, although statoliths undergoing distal-to-side sedimentation began at their highest velocity and slowed monotonically as they approached the lower cell membrane, statoliths crossing the cell's central region remained slow initially and accelerated to maximum speed once they reached a channel. The statoliths accelerated sooner, and the channeling effect was less pronounced in roots treated with cytochalasin D. Parallel ultrastructural studies of high-pressure frozen-freeze-substituted columella cells suggest that the low-resistance statolith pathway in the cell periphery corresponds to the sharp interface between the endoplasmic reticulum (ER)-rich cortical and the ER-devoid central region of these cells. The central region is also shown to contain an actin-based cytoskeletal network in which the individual, straight, actin-like filaments are randomly distributed. To explain these findings as well as the results of physical simulation experiments, we have formulated a new, tensegrity-based model of gravity sensing in columella cells. This model envisages the cytoplasm as pervaded by an actin-based cytoskeletal network that is denser in the ER-devoid central region than in the ER-rich cell cortex and is linked to stretch receptors in the plasma membrane. Sedimenting statoliths are postulated to produce a directional signal by locally disrupting the network and thereby altering the balance of forces acting on the receptors in different plasma membrane regions.

  13. LOCALIZATION OF BRANCHING ENZYME IN POTATO-TUBER CELLS WITH THE USE OF IMMUNOELECTRON MICROSCOPY

    NARCIS (Netherlands)

    KRAM, AM; OOSTERGETEL, GT; VANBRUGGEN, EFJ

    Potato branching enzyme, a key enzyme in the biosynthesis of starch, was localized in amyloplasts in starch-storage cells of potato (Solanum tuberosum L) with the use of immunogold electron microscopy. Branching enzyme was found in the amyloplast stroma, concentrated at the interface of the stroma

  14. Reference: 112 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available ecca A et al. 2004 Oct. Plant Physiol. 136(2):3095-103; discussion 3002. The gravitropism defective 2 (grv2)... mutants of Arabidopsis show reduced shoot phototropism and gravitropism. Amyloplasts in the shoot endoderma...g via amyloplasts sedimentation and the subsequent more general tropic growth response. The gravitropism

  15. A morphometric analysis of the redistribution of organelles in columella cells of horizontally-oriented roots of Zea mays

    Science.gov (United States)

    Moore, R.

    1986-01-01

    In order to determine what structural changes in graviperceptive cells are associated with onset of root gravicurvature, the redistribution of organelles in columella cells of horizontally-oriented, graviresponding roots of Zea mays has been quantified. Root gravicurvature began by 15 min after reorientation, and did not involve significant changes in the (i) volume of individual columella cells or amyloplasts, (ii) relative volume of any cellular organelle, (iii) number of amyloplasts per columella cell, or (iv) surface area of cellular location of endoplasmic reticulum. Sedimentation of amyloplasts began within 1 to 2 min after reorientation, and was characterized by an intensely staining area of cytoplasm adjacent to the sedimenting amyloplasts. By 5 min after reorientation, amyloplasts were located in the lower distal corner of columella cells, and, by 15 min after reorientation, overlaid the entire length of the lower cell wall. No consistent contact between amyloplasts and any cellular structure was detected at any stage of gravicurvature. Centrally-located nuclei initially migrated upward in columella cells of horizontally-oriented roots, after which they moved to the proximal ends of the cells by 15 min after reorientation. No significant pattern of redistribution of vacuoles, mitochondria, dictyosomes, or hyaloplasm was detected that correlated with the onset of gravicurvature. These results indicate that amyloplasts and nuclei are the only organelles whose movements correlate positively with the onset of gravicurvature by primary roots of this cultivar of Zea mays.

  16. Actin microfilaments in presumptive statocytes of root caps and coleoptiles

    Science.gov (United States)

    White, R. G.; Sack, F. D.

    1990-01-01

    Rhodamine-phalloidin was used to determine the distribution of actin microfilament bundles (mfb) in cells thought to be the site of gravity perception (statocytes) in coleoptiles and root caps of Zea mays and Hordeum vulgare. In coleoptile cells, amyloplasts were usually observed in close proximity to thick mfb, which often appeared to divide into finer mfb adjacent to individual amyloplasts. The nucleus in these cells was surrounded by an extensive network of mfb, which were connected to thicker transvacuolar mfb. Columella cells of the root cap contained an extensive reticulum of fine mfb throughout the protoplast, but lacked the much thicker mfb seen in coleoptile cells. The distribution and extent of mfb observed in fixed cells correlates with patterns of streaming and amyloplast movement seen in living cells. A possible role for actin mfb in the perception of gravity is discussed.

  17. Gravity-regulated formation of the peg in developing cucumber seedlings

    Science.gov (United States)

    Takahashi, H.; Scott, T. K.

    1994-01-01

    It has been proposed that peg formation in the vascular transition region (TR zone) between the hypocotyl and the root in Cucurbitaceae seedlings is a gravimorphogenetic phenomenon. Initiation of the peg became visible 36 h after imbibition when cucumber (Cucumis sativus L. cv. Burpee Hybrid II) seeds were germinated in a horizontal position at 24 degrees C in the dark. Simultaneously, sedimented amyloplasts (putative statoliths) were apparent in the sheath cells surrounding the vascular strands, and in the cortical cells immediately adjacent to them, in the TR zone. In contrast, the other cortical cells, some of which were destined to develop into the peg, contained amyloplasts which were not sedimented. These results suggest that the graviperception mechanism for peg formation may be like that of statoliths in shoot gravitropism. By 48 h following imbibition, the cells of the TR zone still had sedimented amyloplasts but had lost their sensitivity to gravity, possibly because of their maturation.

  18. The relationship between profiles of plagiogravitropism and morphometry of columella cells during the development of lateral roots of Vigna angularis

    Science.gov (United States)

    Kuya, Noriyuki; Sato, Seiichi

    2011-02-01

    There has been no convincing explanation on a mechanism inducing plagiogravitropism of lateral roots. The present work deals with gravitropic features of Vignaangularis lateral roots during the course of their growth and morphometric analysis of root caps, columella cells and amyloplasts. Regardless of the magnitude of deviation of the primary root axis from the gravity vector, the newly emerging lateral roots tended to keep a constant angle to the gravity vector. They modified gravireaction several times during the course of their development: a first horizontal-growth stage when they grow in the cortex of primary roots (stage I), a sloping-down growth stage from their emergence to a length of about 1 mm (stage II), a second horizontal-growth stage from a length of about 1 mm to that of over 4 mm (stage III) and a curving-down stage thereafter (stage IV). The columella cells with amyloplasts large enough to sediment were not fully differentiated in the stage I but the turning point from the stage I to II was associated with the development of amyloplasts which were able to sediment toward the distal part of the cell. Amyloplasts were significantly small in the lateral roots over 10 mm long compared with those in ones 0-10 mm long, suggesting that they rapidly develop immediately after the lateral roots emerge from primary roots and then gradually decrease their size when the lateral roots grow over 10 mm long. This dimensional decrease of amyloplasts may be partially involved in weak gravireaction in the stage III. Evidence was not presented indicating that a switchover from the stage III to IV was connected with the dimension of root caps, the number of columella cells and the development of amyloplasts. Some factors at the molecular level rather than at the cellular and tissue levels are probably dominant to induce the stage IV.

  19. Investigation of Starch Binding Domains for Improvement of Starch degradation

    DEFF Research Database (Denmark)

    Christiansen, Camilla

    Dansk resume Stivelse er planternes primære energilager og et vigtigt næringsmiddel for pattedyr,svampe og bakterier. Stivelse deponeres i højt organiserede semi-krystallinske stivelseskorn i plastider: kloroplaster i blade (transitorisk stivelse) og amyloplaster i lagerorganer som knolde. Stivel...

  20. Kinetics of starch digestion and performance of broiler chickens

    NARCIS (Netherlands)

    Weurding, R.E.

    2002-01-01

    Keywords: starch, digestion rate, broiler chickens, peas, tapioca

    Starch is stored in amyloplasts of various plants like cereals and legumes and seeds of these plants are used as feedstuffs for farm animals. Starch is the major energy

  1. Effects of Nitrogen Application Time on Caryopsis Development and Grain Quality of Rice Variety Yangdao 6

    Directory of Open Access Journals (Sweden)

    Fei XIONG

    2008-03-01

    Full Text Available A pot experiment was conducted to study the effects of different nitrogen application time (during the tillering or the booting stages with the same nitrogen rates on the caryopsis development and grain quality of rice variety Yangdao 6. The increased nitrogen fertilizer (urea, especially applied during the booting stage, could evidently increase the milled rice rate, head rice rate and protein content in rice grains compared with the control (no nitrogen application, and decrease chalky grain rate and amylose content. Moreover, the increased nitrogen fertilizer significantly affected the caryopsis development and enhanced the grain weight when nitrogen applied during the tillering and the booting stages, especially during the booting stage. During caryopsis development the increased nitrogen fertilizer applied during the tillering and booting stages could obviously decrease the total starch and amylose contents, but not obviously for the amylopectin content in rice grain. Increased topdressing of nitrogen fertilizer, especially applied during the booting stage, had significant effect on the development and structures of amyloplasts and proteinoplasts. That is, it could change the distribution, number and shape of amyloplasts and proteinoplasts in the endosperm cells especially in grain abdomen. Compared with the control the arrangements of amyloplasts and proteinoplasts were closer, with more numbers, higher density and less interspaces each ohter. Furthermore, most amyloplasts showed polyhedron under the increased nitrogen fertilizer level.

  2. Influence of microgravity on root-cap regeneration and the structure of columella cells in Zea mays

    Science.gov (United States)

    Moore, R.; McClelen, C. E.; Fondren, W. M.; Wang, C. L.

    1987-01-01

    We launched imbibed seeds and seedlings of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on 1) root-cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth-grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth-grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and ellipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar of Z. mays.

  3. Changes in the distribution of plastids and endoplasmic reticulum during cellular differentiation in root caps of Zea mays

    Science.gov (United States)

    Moore, R.; McClelen, C. E.

    1985-01-01

    In calyptrogen cells of Zea mays, proplastids are distributed randomly throughout the cell, and the endoplasmic reticulum (ER) is distributed parallel to the cell walls. The differentiation of calyptrogen cells into columella statocytes is characterized by the following sequential events: (1) formation of ER complexes at the distal and proximal ends of the cell, (2) differentiation of proplastids into amyloplasts, (3) sedimentation of amyloplasts onto the distal ER complex, (4) breakdown of the distal ER complex and sedimentation of amyloplasts to the bottom of the cell, and (5) formation of sheets of ER parallel to the longitudinal cell walls. Columella statocytes located in the centre of the cap each possess 4530 +/- 780 micrometers2 of ER surface area, an increase of 670 per cent over that of calyptrogen cells. The differentiation of peripheral cells correlates positively with (1) the ER becoming arranged in concentric sheets, (2) amyloplasts and ER becoming randomly distributed, and (3) a 280 per cent increase in ER surface area over that of columella statocytes. These results are discussed relative to graviperception and mucilage secretion, which are functions of columella and peripheral cells, respectively.

  4. Tropism in azalea and lily flowers

    Science.gov (United States)

    Shimizu, M.; Tomita-Yokotani, K.; Nakamura, T.; Yamashita, M.

    Tropic responses were examined in azalea Rhododendrom pulchrum and lily Lilium cv. 'Casablanca' flowers. Orientation of the flowers in these two species depicts several up/down characteristics, such as angle of the corolla opening, alignment or configuration of a specific petal at the top, plus direction in the curved tip of the pistil and stamen. Gravity was found to be the prime factor, with light as a secondary signal that determines gravitropism in the pistil of the azalea. Within the azalea, sedimented amyloplasts were observed throughout the cells along the inner layers below the epidermis. In lily flowers, no sedimented amyloplasts were found in style cells, and phototropic responses caused upward bending of the pistil. Responses of lily pistils to monochromatic light were consistent with the action spectrum for phototropism in the shoots of monocotyledonous plants. We discuss how these features may increase the fitness for pollination in these two species.

  5. Transcriptome Analysis Suggests That Starch Synthesis May Proceed via Multiple Metabolic Routes in High Yielding Potato Cultivars

    DEFF Research Database (Denmark)

    Kaminski, Kacper Piotr; Petersen, Annabeth Høgh; Sønderkær, Mads

    2012-01-01

    levels of transcripts for other enzymes involved in starch metabolism in comparison with medium and low yielding cultivars as determined by DeepSAGE transcriptome profiling. The decrease in PGM activity in Kuras was confirmed by measuring the enzyme activity from potato tuber extracts. Contrary......Background: Glucose-6-phosphate is imported into the amyloplast of potato tubers and thought to constitute the precursor for starch synthesis in potato tubers. However, recently it was shown that glucose-1-phosphate can also be imported into the amyloplast and incorporated into starch via an ATP...... independent mechanism under special conditions. Nonetheless, glucose-6-phosphate is believed to be the quantitatively important precursor for starch synthesis in potato. Principical finding: potato tubers of the high yielding cv Kuras had low gene expression of plastidial phophoglucomutase (PGM) and normal...

  6. Photosynthetic Activity in Green Hairy Roots : Ultrastructure of Plastid and Correlation of Chlorophyll and Secondary Metabolites

    OpenAIRE

    Yumio, Toda; Toshio, Aoki; Kayo, Yoshimatsu; Koichiro, Shimomura; Nano-Fabrication Group, Nanomaterial Laboratory, National Institute for Materials Science; Department of Applied Biological Sciences, Nihon University; Tsukuba Medicinal Plant Research Station, National Institute of Health Sciences; Faculty of Life Science, Toyo University

    2002-01-01

    Ultrastructure of the plastid and photosynthetic activity in green hairy roots of Amsonia elliptica, Lippia dulcis and Digitalis lanata were investigated. Plastids observed in A. elliptica were not like normal chloroplasts in leaves or leucoplasts in roots, but an amyloplast-like structure, containing large starch granules with thylakoid membranes around them. In contrast the plastids in D. lanata were chloroplast-like, and just intermediate in L. dulcis. The photosynthetic oxygen evolution a...

  7. Interaction between hydrotropism and gravitropism in seedling roots

    Science.gov (United States)

    Kobayashi, A.; Takahashi, A.; Yamazaki, Y.; Kakimoto, Y.; Higashitani, A.; Fujii, N.; Takahashi, H.

    Roots display positive hydrotropism in response to a moisture gradient, which could play a role in avoiding drought stress. Because roots also respond to other stimuli such as gravity, touch and light and exhibit gravitropism, thigmotropism and phototropism, respectively, their growth orientation is determined by interaction among those tropisms. We have demonstrated the interaction between hydrotropism and gravitropism. For example, 1) agravitropic roots of pea mutant strongly respond to a moisture gradient and show positive hydrotropism by overcoming gravitropism, 2) in wild type pea roots hydrotropism is weak but pronounced when rotated on clinostat, 3) cucumber roots are positively gravitropic on the ground but become hydrotropic in microgravity, and 4) maize roots change their growth direction depending on the intensities of both gravistimulation and hydrostimulation. Here we found that Arabidopsis roots could display strong hydrotropism by overcoming gravitropism. It was discovered that amyloplasts in the columella cells are rapidly degraded upon exposure to a moisture gradient. Thus, degradation of amyloplasts could reduce the responsiveness to gravity, which could pronounce the hydrotropic response. In hydrotropically stimulated roots of pea seedlings, however, we could not observe a rapid degradation of amyloplasts in the columella cells. These results suggest that mechanism underlying the interaction between hydrotropism and gravitropism differs among plant species. To further study the molecular mechanism of hydrotropism and its interaction with gravitropism, we isolated unique mutants of Arabidopsis of which roots showed either ahydrotropism, reduced hydrotropism or negative hydrotropic response and examined their gravitropism, phototropism, waving response, amyloplast degradation and elongation growth. Based on the characterization of hydrotropic mutants, we will attempt to compare the mechanisms of the two tropisms and to clarify their cross talk for

  8. Salt-avoidance tropism in Arabidopsis thaliana

    OpenAIRE

    Li, Xia; Zhang, WS

    2008-01-01

    The orientation of plant root growth is modulated by developmental as well as environmental cues. Among the environmental factors, gravity has been extensively studied because of its overpowering effects in modulating root growth direction. However, our knowledge of the effects of other abiotic signals that influence root growth direction is largely unknown. Recently, we have shown that high salinity can modify root growth direction by inducing rapid amyloplast degradation in root columella c...

  9. Effects of clinorotation and microgravity on sweet clover columella cells treated with cytochalasin D

    Science.gov (United States)

    Hilaire, E.; Paulsen, A. Q.; Brown, C. S.; Guikema, J. A.; Spooner, B. S. (Principal Investigator)

    1995-01-01

    The cytoskeleton of columella cells is believed to be involved in maintaining the developmental polarity of cells observed as a reproducible positioning of cellular organelles. It is also implicated in the transduction of gravitropic signals. Roots of sweet clover (Melilotus alba L.) seedlings were treated with a microfilament disrupter, cytochalasin D, on a slowly rotating horizontal clinostat (2 rpm). Electron micrographs of treated columella cells revealed several ultrastructural effects including repositioning of the nucleus and the amyloplasts and the formation of endoplasmic reticulum (ER) whorls. However, experiments performed during fast clinorotation (55 rpm) showed an accumulation (but no whorling) of a disorganized ER network at the proximal and distal pole and a random distribution of the amyloplasts. Therefore, formation of whorls depends upon the speed of clinorotation, and the overall impact of cytochalasin D suggests the necessity of microfilaments in organelle positioning. Interestingly, a similar drug treatment performed in microgravity aboard the US Space Shuttle Endeavour (STS-54, January 1993) caused a displacement of ER membranes and amyloplasts away from the distal plasma membrane. In the present study, we discuss the role of microfilaments in maintaining columella cell polarity and the utility of clinostats to simulate microgravity.

  10. Induction of Plant Curvature by Magnetophoresis and Cytoskeletal Changes during Root Graviresponse

    Science.gov (United States)

    Hasenstein, Karl H.; Kuznetsov, Oleg A.; Blancaflor, Eilson B.

    1996-01-01

    High gradient magnetic fields (HGMF) induce curvature in roots and shoots. It is considered that this response is likely to be based on the intracellular displacement of bulk starch (amyloplasts) by the ponderomotive force generated by the HGMF. This process is called magnetophoresis. The differential elongation during the curvature along the concave and convex flanks of growing organs may be linked to the microtubular and/or microfilament cytoskeleton. The possible existence of an effect of the HGMF on the cytoskeleton was tested for, but none was found. The application of cytoskeletal stabilizers or depolymerizers showed that neither microtubules, nor microfilaments, are involved in the graviresponse.

  11. Reference: 408 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available o T et al. 2006 Aug. Plant J. 47(4):619-28. Plants can sense the direction of gravity and change the growth ...orientation of their organs. To elucidate the molecular mechanisms of gravity perception and the signal tran...SGR5 promoter revealed that SGR5 is mainly expressed in the endodermis, the gravity-sensing tissue in inflor...f SGR5 using the SCR promoter in the sgr5-1 mutant restores shoot gravitropism indicates that it could function in the gravity...st all amyloplasts in the endodermal cells of the sgr5-1 mutant sedimented in the direction of gravity. Take

  12. Microgravity and clinorotation cause redistribution of free calcium in sweet clover columella cells

    Science.gov (United States)

    Hilaire, E.; Paulsen, A. Q.; Brown, C. S.; Guikema, J. A.; Spooner, B. S. (Principal Investigator)

    1995-01-01

    In higher plants, calcium redistribution is believed to be crucial for the root to respond to a change in the direction of the gravity vector. To test the effects of clinorotation and microgravity on calcium localization in higher plant roots, sweet clover (Melilotus alba L.) seedlings were germinated and grown for two days on a slow rotating clinostat or in microgravity on the US Space Shuttle flight STS-60. Subsequently, the tissue was treated with a fixative containing antimonate (a calcium precipitating agent) during clinorotation or in microgravity and processed for electron microscopy. In root columella cells of clinorotated plants, antimonate precipitates were localized adjacent to the cell wall in a unilateral manner. Columella cells exposed to microgravity were characterized by precipitates mostly located adjacent to the proximal and lateral cell wall. In all treatments some punctate precipitates were associated with vacuoles, amyloplasts, mitochondria, and euchromatin of the nucleus. A quantitative study revealed a decreased number of precipitates associated with the nucleus and the amyloplasts in columella cells exposed to microgravity as compared to ground controls. These data suggest that roots perceive a change in the gravitational field, as produced by clinorotation or space flights, and respond respectively differently by a redistribution of free calcium.

  13. Molecular mechanisms of root gravity sensing and signal transduction.

    Science.gov (United States)

    Strohm, Allison K; Baldwin, Katherine L; Masson, Patrick H

    2012-01-01

    Plants use gravity as a guide to direct their roots down into the soil to anchor themselves and to find resources needed for growth and development. In higher plants, the columella cells of the root tip form the primary site of gravity sensing, and in these cells the sedimentation of dense, starch-filled plastids (amyloplasts) triggers gravity signal transduction. This generates an auxin gradient across the root cap that is transmitted to the elongation zone where it promotes differential cell elongation, allowing the root to direct itself downward. It is still not well understood how amyloplast sedimentation leads to auxin redistribution. Models have been proposed to explain how mechanosensitive ion channels or ligand-receptor interactions could connect these events. Although their roles are still unclear, possible second messengers in this process include protons, Ca(2+), and inositol 1,4,5-triphosphate. Upon gravistimulation, the auxin efflux facilitators PIN3 and PIN7 relocalize to the lower side of the columella cells and mediate auxin redistribution. However, evidence for an auxin-independent secondary mechanism of gravity sensing and signal transduction suggests that this physiological process is quite complex. Furthermore, plants must integrate a variety of environmental cues, resulting in multifaceted relationships between gravitropism and other directional growth responses such as hydro-, photo-, and thigmotropism. Copyright © 2011 Wiley Periodicals, Inc.

  14. Gravity sensing and signal transduction in vascular plant primary roots.

    Science.gov (United States)

    Baldwin, Katherine L; Strohm, Allison K; Masson, Patrick H

    2013-01-01

    During gravitropism, the potential energy of gravity is converted into a biochemical signal. How this transfer occurs remains one of the most exciting mysteries in plant cell biology. New experiments are filling in pieces of the puzzle. In this review, we introduce gravitropism and give an overview of what we know about gravity sensing in roots of vascular plants, with special highlight on recent papers. When plant roots are reoriented sideways, amyloplast resedimentation in the columella cells is a key initial step in gravity sensing. This process somehow leads to cytoplasmic alkalinization of these cells followed by relocalization of auxin efflux carriers (PINs). This changes auxin flow throughout the root, generating a lateral gradient of auxin across the cap that upon transmission to the elongation zone leads to differential cell elongation and gravibending. We will present the evidence for and against the following players having a role in transferring the signal from the amyloplast sedimentation into the auxin signaling cascade: mechanosensitive ion channels, actin, calcium ions, inositol trisphosphate, receptors/ligands, ARG1/ARL2, spermine, and the TOC complex. We also outline auxin transport and signaling during gravitropism.

  15. Gravisensing, apoptosis, and drug recovery in Taxus cell suspensions

    Science.gov (United States)

    Durzan, D. J.

    1999-01-01

    Haploid and diploid cell suspensions of Taxus spp. were examined for their adaptive plasticity in response to simulated microgravity, unit gravity, and hypergravity. Cell suspensions produced the taxane, paclitaxel, (TAXOL (R)), which is useful for the treatment of various cancers. Amyloplasts contributed to taxane ring biosynthesis and to drug release at the cell wall. Drug-producing cells reacted as gravisensing osmotic tensiometers. In stressed cells, amyloplasts docked and fused in clusters to sites on the plasmalemma before taxane discharge into the culture medium. In simulated microgravity and compared to all other treatments, taxane production was reduced nearly 100-fold. The percent paclitaxel of total taxanes remained 3-to 6-fold greater, and biomass doubled. When p53-independent programmed cell death was induced, taxanes were released into the culture medium as free molecules (soluble and insoluble) or bound to membranes, nuclear fragments, xylan residues, and other particulate materials. Unit gravity and especially hypergravity promoted xylogenesis and significant drug overproduction. A model relating families of >touch = (TCH), taxane early response (TER), nuclear cycling, and apoptosis-regulating genes to gravisensing, cell wall modifications, and to taxane recovery accounted for most but not all of the observations.

  16. Transcriptome Analysis Suggests That Starch Synthesis May Proceed via Multiple Metabolic Routes in High Yielding Potato Cultivars

    Science.gov (United States)

    Kaminski, Kacper Piotr; Petersen, Annabeth Høgh; Sønderkær, Mads; Pedersen, Lars Haastrup; Pedersen, Henrik; Feder, Christian; Nielsen, Kåre L.

    2012-01-01

    Background Glucose-6-phosphate is imported into the amyloplast of potato tubers and thought to constitute the precursor for starch synthesis in potato tubers. However, recently it was shown that glucose-1-phosphate can also be imported into the amyloplast and incorporated into starch via an ATP independent mechanism under special conditions. Nonetheless, glucose-6-phosphate is believed to be the quantitatively important precursor for starch synthesis in potato. Principal Finding Potato tubers of the high yielding cv Kuras had low gene expression of plastidial phophoglucomutase (PGM) and normal levels of transcripts for other enzymes involved in starch metabolism in comparison with medium and low yielding cultivars as determined by DeepSAGE transcriptome profiling. The decrease in PGM activity in Kuras was confirmed by measuring the enzyme activity from potato tuber extracts. Contrary to expectations, this combination lead to a higher level of intracellular glucose-1-phosphate (G1P) in Kuras suggesting that G1P is directly imported into plastids and can be quantitatively important for starch synthesis under normal conditions in high yielding cultivars. Significance This could open entirely new possibilities for metabolic engineering of the starch metabolism in potato via the so far uncharacterized G1P transporter. The perspectives are to increase yield and space efficiency of this important crop. In the light of the increasing demands imposed on agriculture to support a growing global population this presents an exciting new possibility. PMID:23284672

  17. The effect of ozone on pollen development in Lolium perenne L

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, K.; Franz, J.-Th.; Masuch, G

    2004-10-01

    Perennial ryegrass plants (Lolium perenne L.) were exposed in 'Closed-Top Chambers' to different ozone concentrations and to charcoal filtered ambient air to study the effect of ozone on the development of pollen. Ozone at ambient (65 nl l{sup -1}, 8 h) and elevated (110 nl l{sup -1}, 4 h) concentrations affected the maturing of pollen by inhibiting starch accumulation in pollen throughout the anther. Affected pollen persisted in the vacuolated state while normal pollen in the same anther were filled with amyloplasts. The percentage of underdeveloped pollen--determined in transversal sections--was significantly higher in exposed plants than in plants grown in filtered air. Results indicate that ozone stress was responsible for the disrupted development of pollen in L. perenne.

  18. Plastid transformation in potato: Solanum tuberosum.

    Science.gov (United States)

    Valkov, Vladimir T; Gargano, Daniela; Scotti, Nunzia; Cardi, Teodoro

    2014-01-01

    Although plastid transformation has attractive advantages and potential applications in plant biotechnology, for long time it has been highly efficient only in tobacco. The lack of efficient selection and regeneration protocols and, for some species, the inefficient recombination using heterologous flanking regions in transformation vectors prevented the extension of the technology to major crops. However, the availability of this technology for species other than tobacco could offer new possibilities in plant breeding, such as resistance management or improvement of nutritional value, with no or limited environmental concerns. Herein we describe an efficient plastid transformation protocol for potato (Solanum tuberosum subsp. tuberosum). By optimizing the tissue culture system and using transformation vectors carrying homologous potato flanking sequences, we obtained up to one transplastomic shoot per bombardment. Such efficiency is comparable to that usually achieved in tobacco. The method described in this chapter can be used to regenerate potato transplastomic plants expressing recombinant proteins in chloroplasts as well as in amyloplasts.

  19. The Quest for Golden Bananas: Investigating Carotenoid Regulation in a Fe'i Group Musa Cultivar.

    Science.gov (United States)

    Buah, Stephen; Mlalazi, Bulukani; Khanna, Harjeet; Dale, James L; Mortimer, Cara L

    2016-04-27

    The regulation of carotenoid biosynthesis in a high-carotenoid-accumulating Fe'i group Musa cultivar, "Asupina", has been examined and compared to that of a low-carotenoid-accumulating cultivar, "Cavendish", to understand the molecular basis underlying carotenogenesis during banana fruit development. Comparisons in the accumulation of carotenoid species, expression of isoprenoid genes, and product sequestration are reported. Key differences between the cultivars include greater carotenoid cleavage dioxygenase 4 (CCD4) expression in "Cavendish" and the conversion of amyloplasts to chromoplasts during fruit ripening in "Asupina". Chromoplast development coincided with a reduction in dry matter content and fruit firmness. Chromoplasts were not observed in "Cavendish" fruits. Such information should provide important insights for future developments in the biofortification and breeding of banana.

  20. [Enhancement of photoassimilate utilization by manipulation of the ADPglucose pyrophosphorylase gene]. Progress report, [March 15, 1989--April 14, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Okita, T.W.

    1990-12-31

    The long term aim of this project is to assess the feasibility of increasing the conversion of photosynthate into starch via manipulation of the gene that encodes for ADPglucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis. In developing storage tissues such as cereal seeds and tubers, starch biosynthesis is regulated by the gene activation and expression of ADPglucose pyrophosphorylase, starch synthase, branching enzyme and other ancillary starch modifying enzymes, as well as the allosteric-controlled behavior of ADPglucose pyrophosphorylase activity. During the last two years we have obtained information on the structure of this enzyme from both potato tuber and rice endosperm, using a combination of biochemical and molecular biological approaches. Moreover, we present evidence that this enzyme may be localized at discrete regions of the starch grain within the amyloplast, and plays a role in controlling overall starch biosynthesis in potato tubers.

  1. Ultrastructure of central cell in female gametophyte of Castilleja wightii Elmer (Scrophulariaceae).

    Science.gov (United States)

    Ekici, Nuran; Dane, Feruzan; Olgun, Göksel

    2013-09-01

    Embryo sac cells are highly differentiated in plants. The central cell is one of the most important cells of the embryo sac. It forms endosperm by fusion with a sperm cell. Ultrastructure of the central cell in the mature embryo sac of Castilleja wightii was investigated in this study. Nucleolus which had a lot of vacuole in a large secondary nucleus and numerous dictyosomes, vesicles, mitochondria, amyloplasts in cytoplasm were seen in this cell. Also free ribosomes in the form of polysomes and large lipid bodies were detected in the cytoplasm. Numerous vacuoles of different size were observed and some of them had autophagic function. Both smooth and rough endoplasmic reticulums were seen. Although invaginations were seen in the plasmalemma of the central cell to the inside of the embryo sac, a thick cuticular layer was observed outer side on the cell wall. The aim of this study was to contribute studies about the ultrastructure of embryo sacs.

  2. Phototropism and gravitropism in lateral roots of Arabidopsis

    Science.gov (United States)

    Kiss, John Z.; Miller, Kelley M.; Ogden, Lisa A.; Roth, Kelly K.

    2002-01-01

    Gravitropism and, to a lesser extent, phototropism have been characterized in primary roots, but little is known about structural/functional aspects of these tropisms in lateral roots. Therefore, in this study, we report on tropistic responses in lateral roots of Arabidopsis thaliana. Lateral roots initially are plagiogravitropic, but when they reach a length of approximately 10 mm, these roots grow downward and exhibit positive orthogravitropism. Light and electron microscopic studies demonstrate a correlation between positive gravitropism and development of columella cells with large, sedimented amyloplasts in wild-type plants. Lateral roots display negative phototropism in response to white and blue light and positive phototropism in response to red light. As is the case with primary roots, the photoresponse is weak relative to the graviresponse, but phototropism is readily apparent in starchless mutant plants, which are impaired in gravitropism. To our knowledge, this is the first report of phototropism of lateral roots in any plant species.

  3. Gravitropism in leaves of Arabidopsis thaliana (L.) Heynh.

    Science.gov (United States)

    Mano, Eriko; Horiguchi, Gorou; Tsukaya, Hirokazu

    2006-02-01

    In higher plants, stems and roots show negative and positive gravitropism, respectively. However, current knowledge on the graviresponse of leaves is lacking. In this study, we analyzed the positioning and movement of rosette leaves of Arabidopsis thaliana under light and dark conditions. We found that the radial positioning of rosette leaves was not affected by the direction of gravity under continuous white light. In contrast, when plants were shifted to darkness, the leaves moved upwards, suggesting negative gravitropism. Analysis of the phosphoglucomutase and shoot gravitropism 2-1 mutants revealed that the sedimenting amyloplasts in the leaf petiole are important for gravity perception, as is the case in stems and roots. In addition, our detailed physiological analyses revealed a unique feature of leaf movement after the shift to darkness, i.e. movement could be divided into negative gravitropism and nastic movement. The orientation of rosette leaves is ascribed to a combination of these movements.

  4. Isolation of cyanophycin from tobacco and potato plants with constitutive plastidic cphATe gene expression.

    Science.gov (United States)

    Neubauer, Katja; Hühns, Maja; Hausmann, Tina; Klemke, Friederike; Lockau, Wolfgang; Kahmann, Uwe; Pistorius, Elfriede K; Kragl, Udo; Broer, Inge

    2012-03-31

    A chimeric cyanophycin synthetase gene composed of the cphATe coding region from the cyanobacterium Thermosynechococcus elongatus BP-1, the constitutive 35S promoter and the plastid targeting sequence of the integral photosystem II protein PsbY was transferred to the tobacco variety Petit Havanna SRI and the commercial potato starch production variety Albatros. The resulting constitutive expression of cyanophycin synthetase leads to polymer contents in potato leaf chloroplasts of up to 35 mg/g dry weight and in tuber amyloplasts of up to 9 mg/g dry weight. Both transgenic tobacco and potato were used for the development of isolation methods applicable for large-scale extraction of the polymer. Two different procedures were developed which yielded polymer samples of 80 and 90% purity, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Embryo cell wall properties in relation to development and desiccation in the recalcitrant-seeded Encephalartos natalensis (Zamiaceae) Dyer and Verdoorn.

    Science.gov (United States)

    Woodenberg, Wynston Ray; Pammenter, N W; Farrant, Jill M; Driouich, Azeddine; Berjak, Patricia

    2015-01-01

    Plant cell walls are dynamic entities that may change with development, differ between plant species and tissue type and play an important role in responses to various stresses. In this regard, the present investigation employed immunocytochemistry to determine wall composition and possible changes during development of immature and mature embryos of the recalcitrant-seeded cycad Encephalartos natalensis. Fluorescent and gold markers, together with cryo-scanning and transmission electron microscopy (TEM) were also used to analyse potential changes in the cell walls of mature embryos upon desiccation. Immature cell walls were characterised by low- and high methyl-esterified epitopes of pectin, rhamnogalacturonan-associated arabinan, and the hemicellulose xyloglucan. Arabinogalactan protein recognised by the LM2 antibody, along with rhamnogalacturonan-associated galactan and the hemicellulose xylan, were not positively localised using immunological probes, suggesting that the cell walls of the embryo of E. natalensis do not possess these epitopes. Interestingly, mature embryos appeared to be identical to immature ones with respect to the cell wall components investigated, implying that these may not change during the protracted post-shedding embryogenesis of this species. Drying appeared to induce some degree of cell wall folding in mature embryos, although this was limited by the abundant amyloplasts, which filled the cytomatrical space. Folding, however, was correlated with relatively high levels of wall plasticisers typified by arabinose polymers. From the results of this study, it is proposed that the embryo cell walls of E. natalensis are constitutively prepared for the flexibility required during cell growth and expansion, which may also facilitate the moderate cell wall folding observed in mature embryos upon drying. This, together with the abundant occurrence of amyloplasts in the cytomatrix, may provide sufficient mechanical stabilisation if water is lost

  6. Statolith action by the numbers: Physics and feasbility

    Science.gov (United States)

    Todd, Paul; Yoder, Thomas; Staehelin, L. Andrew

    2016-07-01

    All modern (and ancient) studies make it clear that statolith motion is required for gravisensing, and some evidence indicates a role for statolith-microfilament interaction. In this study two components of statolith action are considered quantitatively: (1) the movement of statoliths through the columella cell cytoplasm and (2) forces at the site of action of the statolith. (1) Statoliths move through the cytoplasm in the presence of viscous and elastic forces that may be considered separately. The viscous component may be characterized as a solution with a viscosity of approximately 40 centiPoise. Statoliths are deflected from perfectly vertical trajectories by various obstacles, including actin filaments, and their velocities are influenced by interactions between statoliths. Channeling flow is commonly observed, but this cannot be due to the breaking of actin filaments by the force of the sedimenting statolith, as about 600 pN force is required to break a filament, and the force due to gravity on the amyloplast is about 0.07 pN. Under least viscous conditions the randomly-directed Brownian diffusion velocity of the amyloplast is about 10% the sedimentation velocity. (2) Intimate association of statoliths with the cortical ER region requiring gravitational force is postulated. Thin-section micrographs clearly show an interface between the cortex and the central cytoplasm of the columella cell in vascular plant species that have been studied. Whether or not an exchange of chemical components is required, experiments, including observations in low gravity, have demonstrated that the statolith is shallowly embedded in this cortical region to the extent that deformation occurs consistent with Newton's third law. Relieving the gravitational force results in instantaneous motion of the amyloplast away from the cortex. The following inquiry was made concerning the physics at the interface between the statolith and the material of the cortical ER region. How much force

  7. Displacement of organelles in plant gravireceptor cells by vibrational forces and ultrasound.

    Science.gov (United States)

    Kuznetsov, O.; Nechitailo, G.; Kuznetsov, A.

    Plant gravity perception can be studied by displacing statoliths inside receptor cells by forces other than gravity. Due to mechanical heterogeneity of statocytes various ponderomotive forces can be used for this purpose. In a plant subjected to non- symmetric vibrations statoliths experience inertial force proportional to the difference between their density and that of cytoplasm and to the instantaneous acceleration of the cell. This force causes cyclic motion of statoliths relative to cytoplasm and, depending on the profile of oscillations, can result in a net displacement of them (due to complex rheology of the cell interior), similar to sedimentation. This can be described as "vibrational" ponderomotive force acting on the statoliths. Vertically growing Arabidopsis seedlings, subjected to horizontal, sawtooth shaped oscillations (250 Hz, 1.5 mm amplitude), showed 17+/-2o root curvature toward and shoot curvature of 11+/-3o against the stronger acceleration. When the polarity of the oscillations was reversed, the direction of curvature of shoots and roots was also reversed. Control experiments with starchless mutants (TC7) produced no net curvature, which indicates that dense starch-filled amyloplasts are needed for the effect. These control experiments also eliminate touch-induced reactions or other side-effects as the cause of the curvature. Linum roots curved 25+/-7o . Ceratodon protonemata subjected to the same oscillations have shown displacement of plastids and curvature consistent with the pattern observed during graviresponse: positively gravitropic wwr mutant curved in the direction of the plastid displacement, WT curved in the opposite direction. Acoustic ponderomotive forces, originating from transfer of a sonic beam momentum to the medium due to sound scattering and attenuation in a mechanically heterogeneous system, also can displace statoliths. Vertical flax seedlings curved away from the ultrasonic source (800 kHz, 0.1 W/cm2 ) presumably as a

  8. Some effects of high- gradient magnetic field on tropism of roots of higher plants

    Science.gov (United States)

    Kondrachuk, A.; Belyavskaya, N.

    The perception of gravity in living organisms is mostly based on the response of the gravisensing system to displacement of some specific mass caused by gravitational force. According to the starch-statolith hypothesis the amyloplasts play the role of specific mass in gravisensing cells of higher plants. Kuznetsov & Hasenstein (1996) have demonstrated that the high-gradient magnetic field (HGMF) exerts a directional ponderomotive force on diamagnetic substances, in particular, statoliths. This effect of the HGMF causes root response similar to that produced by the change in gravity vector. Their studies supported the starch-statolith hypothesis and showed that ponderomotive force can be used to modify force acting on statoliths by manipulating statolith locations within gravisensing cells. We have designed the HGMF facility that allows for generating the HGMF and analyzing its effects on higher plants' roots. It records by videosystem and measures with the help of image analysis software the parameters of kinetics of root bending under both the HGMF action and gravistimulation. Two species of plants (pea and cress) have been examined. The main results of the work are the following: 1) The magnetotropic effect of HGMF on root growth was found for both species. 2) The critical value of ponderomotive force that caused the magnetotropic effect was estimated by modeling the magnetic field spatial distribution in the region of root apex. 3) The electron-microscopic analysis of statocytes after the HGMF treatment was carried out. The displacement of amyloplasts in root statocytes of two species of plants in HGMF was firstly demonstrated at the ultrastructural level. 4) Spatial distribution of exogenous proton fluxes (pH) along the roots was studied. The changes in pH distribution along curvature zone and apices of roots were revealed in the HGMF. It is known that application of HGMFs or strong uniform magnetic fields may influence ion transport due to Ampere force. It

  9. Root cytoskeleton: its role in perception of and response to gravity

    Science.gov (United States)

    Baluska, F.; Hasenstein, K. H.

    1997-01-01

    We have critically evaluated the possible functions of the plant cytoskeleton in root gravisensing and graviresponse and discussed the evidence that microtubules (MTs) and actin microfilaments (MFs) do not control differential cell growth during bending of roots. On the other hand, MF and MT networks are envisaged to participate in gravisensing because of the mechanical properties of the cytoskeletal structures that interconnect plant cell organelles with the plasma membrane. In restrained gravisensing, forces are suggested to be transmitted to membranes because large-scale gravity-dependent repositioning of organelles is effectively prevented due to the cytoskeleton-mediated anchorage of their envelopes at the plasma membrane. From the cytoskeletal point of view, we can also envisage an unrestrained gravity sensing when cytoskeletal tethers are not strong enough to preserve the tight control over distribution of organelles and the latter, if heavy enough, are allowed to sediment towards the physical bottom of cells. This situation obviously occurs in root cap statocytes because these uniquely organized cells are depleted of prominent actin MF bundles, endoplasmic MT arrays, and ER elements in their internal cytoplasm. Nevertheless, indirect evidence clearly indicates that sedimented root cap statoliths are enmeshed within fine but dynamic MF networks and that their behaviour is obviously under, at least partial, cytoskeletal control. The actomyosin-enriched domain among and around amyloplasts is proposed to increase the perception of gravity due to the grouping effect of sedimenting statoliths. Cytoskeletal links between myosin-rich statoliths, and cell peripheries well equipped with dense cortical MTs, membrane-associated cytoskeleton, as well as with ER elements, would allow efficient restrained gravisensing only at the statocyte cell cortex. As a consequence of cytoskeletal depletion in the internal statocyte cytoplasm and bulk sedimentation of large

  10. Plastidial α-glucan phosphorylase 1 complexes with disproportionating enzyme 1 in Ipomoea batatas storage roots for elevating malto-oligosaccharide metabolism.

    Science.gov (United States)

    Lin, Yi-Chen; Chang, Shih-Chung; Juang, Rong-Huay

    2017-01-01

    It has been proposed that malto-oligosaccharides (MOSs) are possibly recycled back into amylopectin biosynthesis via the sequential reactions catalyzed by plastidial α-glucan phosphorylase 1 (Pho1) and disproportionating enzyme 1 (Dpe1). In the present study, the reciprocal co-immunoprecipitation experiments using specific antibodies against Pho1 and Dpe1 demonstrated that these two enzymes can form a complex (the PD complex) in Ipomoea batatas storage roots. The immunohistochemistry analyses also revealed the co-localization of Pho1 and Dpe1 in the amyloplasts, and the protein levels of Pho1 and Dpe1 increased gradually throughout sweet potato storage root development. A high molecular weight PD complex was co-purified from sweet potato storage root lysates by size exclusion chromatography. Enzyme kinetic analyses showed that the PD complex can catalyze maltotriose and maltotetraose to generate glucose-1-phosphate in the presence of inorganic phosphate, and it also performs greater Dpe1 activity toward MOSs than does free form Dpe1. These data suggest that Pho1 and Dpe1 may form a metabolon complex, which provides elevated metabolic fluxes for MOS metabolism via a direct transfer of sugar intermediates, resulting in recycling of glucosyl units back into amylopectin biosynthesis more efficiently.

  11. Characterization of chromoplasts and carotenoids of red- and yellow-fleshed papaya (Carica papaya L.).

    Science.gov (United States)

    Schweiggert, Ralf M; Steingass, Christof B; Heller, Annerose; Esquivel, Patricia; Carle, Reinhold

    2011-11-01

    Chromoplast morphology and ultrastructure of red- and yellow-fleshed papaya (Carica papaya L.) were investigated by light and transmission electron microscopy. Carotenoid analyses by LC-MS revealed striking similarity of nutritionally relevant carotenoid profiles in both the red and yellow varieties. However, while yellow fruits contained only trace amounts of lycopene, the latter was found to be predominant in red papaya (51% of total carotenoids). Comparison of the pigment-loaded chromoplast ultrastructures disclosed tubular plastids to be abundant in yellow papaya, whereas larger crystalloid substructures characterized most frequent red papaya chromoplasts. Exclusively existent in red papaya, such crystalloid structures were associated with lycopene accumulation. Non-globular carotenoid deposition was derived from simple solubility calculations based on carotenoid and lipid contents of the differently colored fruit pulps. Since the physical state of carotenoid deposition may be decisive regarding their bioavailability, chromoplasts from lycopene-rich tomato fruit (Lycopersicon esculentum L.) were also assessed and compared to red papaya. Besides interesting analogies, various distinctions were ascertained resulting in the prediction of enhanced lycopene bioavailability from red papaya. In addition, the developmental pathway of red papaya chromoplasts was investigated during fruit ripening and carotenogenesis. In the early maturation stage of white-fleshed papaya, undifferentiated proplastids and globular plastids were predominant, corresponding to incipient carotenoid biosynthesis. Since intermediate plastids, e.g., amyloplasts or chloroplasts, were absent, chromoplasts are likely to emerge directly from proplastids.

  12. Transcriptional and Hormonal Regulation of Gravitropism of Woody Stems in Populus.

    Science.gov (United States)

    Gerttula, Suzanne; Zinkgraf, Matthew; Muday, Gloria K; Lewis, Daniel R; Ibatullin, Farid M; Brumer, Harry; Hart, Foster; Mansfield, Shawn D; Filkov, Vladimir; Groover, Andrew

    2015-10-01

    Angiosperm trees reorient their woody stems by asymmetrically producing a specialized xylem tissue, tension wood, which exerts a strong contractile force resulting in negative gravitropism of the stem. Here, we show, in Populus trees, that initial gravity perception and response occurs in specialized cells through sedimentation of starch-filled amyloplasts and relocalization of the auxin transport protein, PIN3. Gibberellic acid treatment stimulates the rate of tension wood formation and gravibending and enhances tissue-specific expression of an auxin-responsive reporter. Gravibending, maturation of contractile fibers, and gibberellic acid (GA) stimulation of tension wood formation are all sensitive to transcript levels of the Class I KNOX homeodomain transcription factor-encoding gene ARBORKNOX2 (ARK2). We generated genome-wide transcriptomes for trees in which gene expression was perturbed by gravistimulation, GA treatment, and modulation of ARK2 expression. These data were employed in computational analyses to model the transcriptional networks underlying wood formation, including identification and dissection of gene coexpression modules associated with wood phenotypes, GA response, and ARK2 binding to genes within modules. We propose a model for gravitropism in the woody stem in which the peripheral location of PIN3-expressing cells relative to the cambium results in auxin transport toward the cambium in the top of the stem, triggering tension wood formation, while transport away from the cambium in the bottom of the stem triggers opposite wood formation. © 2015 American Society of Plant Biologists. All rights reserved.

  13. Microtubules restrict plastid sedimentation in protonemata of the moss Ceratodon

    Science.gov (United States)

    Schwuchow, J.; Sack, F. D.

    1994-01-01

    Apical cells of protonemata of the moss Ceratodon purpureus are unusual among plant cells with sedimentation in that only some amyloplasts sediment and these do not fall completely to the bottom of vertical cells. To determine whether the cytoskeleton restricts plastid sedimentation, the effects of amiprophos-methyl (APM) and cytochalasin D (CD) on plastid position were quantified. APM treatments of 30-60 min increased the plastid sedimentation that is normally seen along the length of untreated or control cells. Longer APM treatments often resulted in more dramatic plastid sedimentation, and in some cases almost all plastids sedimented to the lowermost point in the cell. In contrast, the microfilament inhibitor CD did not affect longitudinal plastid sedimentation compared to untreated cells, although it did disturb or eliminate plastid zonation in the tip. These data suggest that microtubules restrict the sedimentation of plastids along the length of the cell and that microtubules are load-bearing for all the plastids in the apical cell. This demonstrates the importance of the cytoskeleton in maintaining organelle position and cell organization against the force of gravity.

  14. Auxin, ethylene and light in gravitropic growth: new insights

    Science.gov (United States)

    Edelmann, Hg; Sabovljevic, A.; Njio, G.; Roth, U.

    The regulation mechanism of gravitropic differential plant growth is commonly divided into three sequential processes: the perception of the gravistimulus (generally attributed to amyloplast sedimentation), the transduction of the perceived signal (of which very little is known), and the adequate differential growth response (generally attributed to asymmetric auxin redistribution). The detailled mechanism is still unresolved and remains to be elucidated in significant parts. Employing 2D SDS-PAGE /Q-TOF amongst other methods and strategies we studied the effect of different auxins on gravitropism of coleoptiles and hypocotyls. We also analyzed the effects of light and ethylene (synthesis and perception) on gravitropic growth of primary shoots and roots and analyzed the protein pattern with respect to the observed physiological effects. In coleoptiles, under the applied experimental conditions the effect of 2,4-dichlorophenoxy acetic acid (2,4 D) on gravitropism differed from the effect of indolylacetic acid (IAA), which was similar to the one observed in sunflower hypocotyls. In roots, the relevance of ethylene for gravitropic differential growth and the capacity to evade mechanical barriers during horizontal gravistimulation was analyzed in detail. A special focus was addressed on the physiological significance of the root cap. We will show that the relevance of ethylene for gravitropism has hitherto been misjudged. Further new findings and their implications for the regulation mechanism of gravitropism will be presented and discussed. Kramer et al., (2003) J. Ex. Bot. 54, (393), 2723-2732 Edelmann, H.G., (2002) J. Ex. Bot. 53, (375), 1825-1828

  15. The role of transporters in supplying energy to plant plastids.

    Science.gov (United States)

    Flügge, Ulf-Ingo; Häusler, Rainer E; Ludewig, Frank; Gierth, Markus

    2011-04-01

    The energy status of plant cells strongly depends on the energy metabolism in chloroplasts and mitochondria, which are capable of generating ATP either by photosynthetic or oxidative phosphorylation, respectively. Another energy-rich metabolite inside plastids is the glycolytic intermediate phosphoenolpyruvate (PEP). However, chloroplasts and most non-green plastids lack the ability to generate PEP via a complete glycolytic pathway. Hence, PEP import mediated by the plastidic PEP/phosphate translocator or PEP provided by the plastidic enolase are vital for plant growth and development. In contrast to chloroplasts, metabolism in non-green plastids (amyloplasts) of starch-storing tissues strongly depends on both the import of ATP mediated by the plastidic nucleotide transporter NTT and of carbon (glucose 6-phosphate, Glc6P) mediated by the plastidic Glc6P/phosphate translocator (GPT). Both transporters have been shown to co-limit starch biosynthesis in potato plants. In addition, non-photosynthetic plastids as well as chloroplasts during the night rely on the import of energy in the form of ATP via the NTT. During energy starvation such as prolonged darkness, chloroplasts strongly depend on the supply of ATP which can be provided by lipid respiration, a process involving chloroplasts, peroxisomes, and mitochondria and the transport of intermediates, i.e. fatty acids, ATP, citrate, and oxaloacetate across their membranes. The role of transporters involved in the provision of energy-rich metabolites and in pathways supplying plastids with metabolic energy is summarized here.

  16. Rape embryogenesis. IV. Appearance and disappearance of starch during embryo development

    Directory of Open Access Journals (Sweden)

    Teresa Tykarska

    2014-01-01

    Full Text Available Starch appears first in the suspensor of the proembryo with two-cell apical part. It is observed in the embryo proper from the octant stage. At first it is visible in all the embryo cells in the form of minute transient grains which disappear during cell divisions. But the columella mother cells and their derivatives have persistent large grains. When the embryo turns green in the heart stage a gradual accumulation of storage starch begins and lasts to the end of embryogenesis. Storage starch grains appear first in the auter cortex layers of the hypocotyl where the largest grains are to be found later, and afterwards in all the other tissues. Starch is usually absent in the frequently dividing cells, but even there it appears in the form of minute grains after the end of cell divisions. Disappearance of starch starts when the intensive green colour of the seed coat begins to fade. The first to disappear are the smallest granules in the regions where they were noted latest. In the embryo axis the starch grains remain deposited longest in dermatogen and cortex cells in the lower hypocotyl part. They are visible there, still when the seed turns brown. In black seeds starch may be only found in the columella the cells of which throughout embryogenesis contain amyloplasts filled with starch. These grains disappear completely at the time when the seeds become dry.

  17. Starch Biosynthesis in the Developing Endosperms of Grasses and Cereals

    Directory of Open Access Journals (Sweden)

    Ian J. Tetlow

    2017-12-01

    Full Text Available The starch-rich endosperms of the Poaceae, which includes wild grasses and their domesticated descendents the cereals, have provided humankind and their livestock with the bulk of their daily calories since the dawn of civilization up to the present day. There are currently unprecedented pressures on global food supplies, largely resulting from population growth, loss of agricultural land that is linked to increased urbanization, and climate change. Since cereal yields essentially underpin world food and feed supply, it is critical that we understand the biological factors contributing to crop yields. In particular, it is important to understand the biochemical pathway that is involved in starch biosynthesis, since this pathway is the major yield determinant in the seeds of six out of the top seven crops grown worldwide. This review outlines the critical stages of growth and development of the endosperm tissue in the Poaceae, including discussion of carbon provision to the growing sink tissue. The main body of the review presents a current view of our understanding of storage starch biosynthesis, which occurs inside the amyloplasts of developing endosperms.

  18. Expression of an engineered granule-bound Escherichia coli maltose acetyltransferase in wild-type and amf potato plants.

    Science.gov (United States)

    Nazarian Firouzabadi, Farhad; Vincken, Jean-Paul; Ji, Qin; Suurs, Luc C J M; Visser, Richard G F

    2007-01-01

    Starch is used in many industrial applications, but often requires chemical derivatization to enhance its properties before use. In particular, the stability of starch polymers in solution is improved by acetylation. A drawback of this treatment is the use of pollutant chemicals. A biological alternative to chemical derivatization was investigated by the expression of an amyloplast-targeted Escherichia coli maltose acetyltransferase (MAT) gene in tubers of wild-type (Kardal) and mutant amylose-free (amf) potato plants. MAT was expressed as such, or fused to the N- or C-terminus of a non-catalytic starch-binding domain (SBD) to target the starch granule. Starch granules derived from transgenic plants were found to contain acetyl groups, although their content was low, opening up an avenue to move away from the post-harvest chemical derivatization of starch. MAT inside starch granules was found to be active post-harvest when supplied with acetyl-coenzyme A and glucose or maltose, but it did not acetylate starch polymers in vitro. Starch granules from transformants in which MAT alone was expressed also showed MAT activity, indicating that MAT is accumulated in starch granules, and has affinity for starch by itself. Furthermore, starch granule morphology was altered, and fusion proteins containing MAT and SBD seemed to have a higher affinity for starch granules than two appended SBDs. These results are discussed against the background of the quaternary structure of MAT.

  19. Post-harvest light treatment increases expression levels of recombinant proteins in transformed plastids of potato tubers.

    Science.gov (United States)

    Larraya, Luis M; Fernández-San Millán, Alicia; Ancín, María; Farran, Inmaculada; Veramendi, Jon

    2015-09-01

    Plastid genetic engineering represents an attractive system for the production of foreign proteins in plants. Although high expression levels can be achieved in leaf chloroplasts, the results for non-photosynthetic plastids are generally discouraging. Here, we report the expression of two thioredoxin genes (trx f and trx m) from the potato plastid genome to study transgene expression in amyloplasts. As expected, the highest transgene expression was detected in the leaf (up to 4.2% of TSP). The Trx protein content in the tuber was approximately two to three orders of magnitude lower than in the leaf. However, we demonstrate that a simple post-harvest light treatment of microtubers developed in vitro or soil-grown tubers induces up to 55 times higher accumulation of the recombinant protein in just seven to ten days. After the applied treatment, the Trx f levels in microtubers and soil-grown tubers increased to 0.14% and 0.11% of TSP, respectively. Moreover, tubers stored for eight months maintained the capacity of increasing the foreign protein levels after the light treatment. Post-harvest cold induction (up to five times) at 4°C was also detected in microtubers. We conclude that plastid transformation and post-harvest light treatment could be an interesting approach for the production of foreign proteins in potato. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Dynamics of vegetative cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana

    Science.gov (United States)

    Kuang, A.; Musgrave, M. E.

    1996-01-01

    Ultrastructural changes of pollen cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana were studied. The pollen cytoplasm develops a complicated ultrastructure and changes dramatically during these stages. Lipid droplets increase after generative cell formation and their organization and distribution change with the developmental stage. Starch grains in amyloplasts increase in number and size during generative and sperm cell formation and decrease at pollen maturity. The shape and membrane system of mitochondria change only slightly. Dictyosomes become very prominent, and numerous associated vesicles are observed during and after sperm cell formation. Endoplasmic reticulum appears extensively as stacks during sperm cell formation. Free and polyribosomes are abundant in the cytoplasm at all developmental stages although they appear denser at certain stages and in some areas. In mature pollen, all organelles are randomly distributed throughout the vegetative cytoplasm and numerous small particles appear. Organization and distribution of storage substances and appearance of these small particles during generative and sperm cell formation and pollen maturation are discussed.

  1. Proteome Profile of Starch Granules Purified from Rice (Oryza sativa) Endosperm.

    Science.gov (United States)

    Xing, Shihai; Meng, Xiaoxi; Zhou, Lihui; Mujahid, Hana; Zhao, Chunfang; Zhang, Yadong; Wang, Cailin; Peng, Zhaohua

    2016-01-01

    Starch is the most important food energy source in cereals. Many of the known enzymes involved in starch biosynthesis are partially or entirely granule-associated in the endosperm. Studying the proteome of rice starch granules is critical for us to further understand the mechanisms underlying starch biosynthesis and packaging of starch granules in rice amyloplasts, consequently for the improvement of rice grain quality. In this article, we developed a protocol to purify starch granules from mature rice endosperm and verified the quality of purified starch granules by microscopy observations, I2 staining, and Western blot analyses. In addition, we found the phenol extraction method was superior to Tris-HCl buffer extraction method with respect to the efficiency in recovery of starch granule associated proteins. LC-MS/MS analysis showed identification of already known starch granule associated proteins with high confidence. Several proteins reported to be involved in starch synthesis in prior genetic studies in plants were also shown to be enriched with starch granules, either directly or indirectly, in our studies. In addition, our results suggested that a few additional candidate proteins may also be involved in starch synthesis. Furthermore, our results indicated that some starch synthesis pathway proteins are subject to protein acetylation modification. GO analysis and KEGG pathway enrichment analysis showed that the identified proteins were mainly located in plastids and involved in carbohydrate metabolism. This study substantially advances the understanding of the starch granule associated proteome in rice and post translational regulation of some starch granule associated proteins.

  2. The effect of the external medium on the gravitropic curvature of rice (Oryza sativa, Poaceae) roots

    Science.gov (United States)

    Staves, M. P.; Wayne, R.; Leopold, A. C.

    1997-01-01

    The roots of rice seedlings, growing in artificial pond water, exhibit robust gravitropic curvature when placed perpendicular to the vector of gravity. To determine whether the statolith theory (in which intracellular sedimenting particles are responsible for gravity sensing) or the gravitational pressure theory (in which the entire protoplast acts as the gravity sensor) best accounts for gravity sensing in rice roots, we changed the physical properties of the external medium with impermeant solutes and examined the effect on gravitropism. As the density of the external medium is increased, the rate of gravitropic curvature decreases. The decrease in the rate of gravicurvature cannot be attributed to an inhibition of growth, since rice roots grown in 100 Osm/m3 (0.248 MPa) solutions of different densities all support the same root growth rate but inhibit gravicurvature increasingly with increasing density. By contrast, the sedimentation rate of amyloplasts in the columella cells is unaffected by the external density. These results are consistent with the gravitational pressure theory of gravity sensing, but cannot be explained by the statolith theory.

  3. A functional TOC complex contributes to gravity signal transduction in Arabidopsis.

    Science.gov (United States)

    Strohm, Allison K; Barrett-Wilt, Greg A; Masson, Patrick H

    2014-01-01

    Although plastid sedimentation has long been recognized as important for a plant's perception of gravity, it was recently shown that plastids play an additional function in gravitropism. The Translocon at the Outer envelope membrane of Chloroplasts (TOC) complex transports nuclear-encoded proteins into plastids, and a receptor of this complex, Toc132, was previously hypothesized to contribute to gravitropism either by directly functioning as a gravity signal transducer or by indirectly mediating the plastid localization of a gravity signal transducer. Here we show that mutations in multiple genes encoding TOC complex components affect gravitropism in a genetically sensitized background and that the cytoplasmic acidic domain of Toc132 is not required for its involvement in this process. Furthermore, mutations in TOC132 enhance the gravitropic defect of a mutant whose amyloplasts lack starch. Finally, we show that the levels of several nuclear-encoded root proteins are altered in toc132 mutants. These data suggest that the TOC complex indirectly mediates gravity signal transduction in Arabidopsis and support the idea that plastids are involved in gravitropism not only through their ability to sediment but also as part of the signal transduction mechanism.

  4. Plastidial α-glucan phosphorylase 1 complexes with disproportionating enzyme 1 in Ipomoea batatas storage roots for elevating malto-oligosaccharide metabolism

    Science.gov (United States)

    Lin, Yi-Chen; Chang, Shih-Chung; Juang, Rong-Huay

    2017-01-01

    It has been proposed that malto-oligosaccharides (MOSs) are possibly recycled back into amylopectin biosynthesis via the sequential reactions catalyzed by plastidial α-glucan phosphorylase 1 (Pho1) and disproportionating enzyme 1 (Dpe1). In the present study, the reciprocal co-immunoprecipitation experiments using specific antibodies against Pho1 and Dpe1 demonstrated that these two enzymes can form a complex (the PD complex) in Ipomoea batatas storage roots. The immunohistochemistry analyses also revealed the co-localization of Pho1 and Dpe1 in the amyloplasts, and the protein levels of Pho1 and Dpe1 increased gradually throughout sweet potato storage root development. A high molecular weight PD complex was co-purified from sweet potato storage root lysates by size exclusion chromatography. Enzyme kinetic analyses showed that the PD complex can catalyze maltotriose and maltotetraose to generate glucose-1-phosphate in the presence of inorganic phosphate, and it also performs greater Dpe1 activity toward MOSs than does free form Dpe1. These data suggest that Pho1 and Dpe1 may form a metabolon complex, which provides elevated metabolic fluxes for MOS metabolism via a direct transfer of sugar intermediates, resulting in recycling of glucosyl units back into amylopectin biosynthesis more efficiently. PMID:28472155

  5. Ultrastructural features of Mimulus aurantiacus (Scrophulariaceae) pollen tubes in vivo.

    Science.gov (United States)

    Ekici, Nuran; Dane, Feruzan; Olgun, Göksel

    2009-03-01

    The aim of this study is to give information on ultrastructure of in vivo pollen tubes of Mimulus aurantiacus which were collected from the Botanical Garden of the University of California at Berkeley. Materials were prepared according to electron microscopy methods and examined under Zeiss electron microscope. Four zones were examined in the pollen tubes of Mimulus aurantiacus. Apical zone: Mitochondria, smooth endoplasmic reticulum, rough endoplasmic reticulum, dictyosomes and secretory vesicles were observed. Subapical zone: This area contained abundant rough endoplasmic reticulum and occasionally some smooth endoplasmic reticulum. The polysomes, mitochondria, proplastids that contain starch, small vacuoles and a few lipid bodies were detected. Nuclear zone: Both generative and vegetative cell nuclei lie in this zone. The vegetative cell nucleus was large and long. Rough endoplasmic reticulum, mitochondria, ribosomes, dictyosomes, and amyloplasts that are rich of starch were observed. Vacuolation and plug formation zone: Cytoplasm of the tubes was full of large vacuoles. Few organelles such as mitochondria, dictyosome and rough endoplasmic reticulum were detected along their periphery.

  6. Salt-avoidance tropism in Arabidopsis thaliana.

    Science.gov (United States)

    Li, Xia; Zhang, Ws

    2008-05-01

    The orientation of plant root growth is modulated by developmental as well as environmental cues. Among the environmental factors, gravity has been extensively studied because of its overpowering effects in modulating root growth direction. However, our knowledge of the effects of other abiotic signals that influence root growth direction is largely unknown. Recently, we have shown that high salinity can modify root growth direction by inducing rapid amyloplast degradation in root columella cells of Arabidopsis thaliana. By exploiting salt overly sensitive (sos) mutants and PIN2 expression analyses, we have shown that the altered root growth direction in response to salt is mediated by ion disequilibrium and is correlated with PIN2 mRNA abundance and expression and localization of the protein. Our study demonstrates that the SOS pathway may mediate this process. Here we discuss our data from broader perspectives. We propose that salt-induced modification of root growth direction is a salt-avoidance behavior, which is an active adaptive mechanism for plants grown under saline conditions. Furthermore, high salinity also stimulates alteration of gravitropic growth of shoots. These findings illustrate that plants have a fine and sophisticated sensory and communication system that enable plants to dynamically and efficiently cope with rapidly changing environment.

  7. Participation of IAA in transduction of gravistimulus in apical cells of moss protonema

    Science.gov (United States)

    Oksyniuk, U. A.; Khorkavtsiv, O. Y.; Lesniak, Y. I.

    Growth movements of vascular plant axis organs -- photo-, gravi- and other tropisms -- are tightly connected with IAA transport (Hertel, 1983; Medvedev, 1996; Kiss, 2000). Moss protonema synthesizes IAA (indole-3-acetic acid) and transports it basipetally favouring growth and differentiation of caulonema (Bopp, 1979; Rose, Bopp, 1983; Rose et al., 1983). We aimed at studying the role of IAA in moss protonema gravitropism using exogenous IAA, 1-NAA (1-naphthaleneacetic acid), 2,4D (2,4-dichlorophenoxyacetic acid) and inhibitors of polar IAA transport -- phytotropins NPA (N-1-naphthylphthalamic acid) and TIBA (2,3,5-triiodobenzoic acid). Six-day gravitropic protonema of Ceratodon purpureus and Pohlia nutans were taken for experiments. Auxin and phytotropins solutions were laid on protonema mats the latters being kept in solutions for 30 min. Then the surplus of solutions were poured off and Petri dishes were placed vertically for 6 h. 20 μ M of IAA and of other synthetic auxins did not significantly influence the angle of protonema gravity bending, 40 μ M of the agents, howewer, reduced the per cent of apical cells bendings and their angles. The most expressed influence on the angles of bending had the inhibitors of polar IAA transport -- NPA. 0,1 -- 3,0 μ M of this phytotropin did not change the form of apical cell, did not disturb the general distribution of amyloplasts and did not significantly lower the per cent and the value of gravity bending angle, though 10 μ M of the phytotropin - inhibited gravity bending. The mixture of 1-NAA and NPA having been added into the medium the influence of NPA was lowered and gravitropic growth renewed in course of time. 10 μ M of other phytopropin TIBA also inhibited gravitropism of Ceratodon purpureus and Pohlia nutans protonema. The analysis of basipetal transport of IAA in moss rhizoids and protonema may indicate the availability of special IAA transport in these structures (Bopp, Cerier, 1988). On the basis of the

  8. Molecular and biochemical analysis of the plastidic ADP-glucose transporter (ZmBT1) from Zea mays.

    Science.gov (United States)

    Kirchberger, Simon; Leroch, Michaela; Huynen, Martijn A; Wahl, Markus; Neuhaus, H Ekkehard; Tjaden, Joachim

    2007-08-03

    Physiological studies on the Brittle1 maize mutant have provided circumstantial evidence that ZmBT1 (Zea mays Brittle1 protein) is involved in the ADP-Glc transport into maize endosperm plastids, but up to now, no direct ADP-Glc transport mediated by ZmBT1 has ever been shown. The heterologous synthesis of ZmBT1 in Escherichia coli cells leads to the functional integration of ZmBT1 into the bacterial cytoplasmic membrane. ZmBT1 transports ADP-Glc in counterexchange with ADP with apparent affinities of about 850 and 465 mum, respectively. Recently, a complete ferredoxin/thioredoxin system has been identified in cereal amyloplasts and BT1 has been proposed as a potential Trx target protein (Balmer, Y., Vensel, W. H., Cai, N., Manieri, W., Schurmann, P., Hurkman, W. J., and Buchanan, B. B. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 2988-2993). Interestingly, we revealed that the transport activity of ZmBT1 is reversibly regulated by redox reagents such as diamide and dithiothreitol. The expression of ZmBT1 is restricted to endosperm tissues during starch synthesis, whereas a recently identified BT1 maize homologue, the ZmBT1-2, exhibits a ubiquitous expression pattern in hetero- and autotrophic tissues indicating different physiological roles for both maize BT1 isoforms. BT1 homologues are present in both mono- and dicotyledonous plants. Phylogenetic analyses classify the BT1 family into two phylogenetically and biochemically distinct groups. The first group comprises BT1 orthologues restricted to cereals where they mediate the ADP-Glc transport into cereal endosperm storage plastids during starch synthesis. The second group occurs in mono- and dicotyledonous plants and is most probably involved in the export of adenine nucleotides synthesized inside plastids.

  9. New Insights into Fe Localization in Plant Tissues

    Directory of Open Access Journals (Sweden)

    Hannetz eRoschzttardtz

    2013-09-01

    Full Text Available Deciphering cellular iron (Fe homeostasis requires having access to both quantitative and qualitative information on the subcellular pools of Fe in tissues and their dynamics within the cells. We have taken advantage of the Perls/DAB Fe staining procedure to perform a systematic analysis of Fe distribution in roots, leaves and reproductive organs of the model plant Arabidopsis thaliana, using wild-type and mutant genotypes affected in iron transport and storage. Roots of soil-grown plants accumulate iron in the apoplast of the central cylinder, a pattern that is strongly intensified when the citrate effluxer FRD3 is not functional, thus stressing the importance of citrate in the apoplastic movement of Fe. In leaves, Fe level is low and only detected in and around vascular tissues. In contrast, Fe staining in leaves of iron-treated plants extends in the surrounding mesophyll cells where Fe deposits, likely corresponding to Fe-ferritin complexes, accumulate in the chloroplasts. The loss of ferritins in the fer1,3,4 triple mutant provoked a massive accumulation of Fe in the apoplastic space, suggesting that in the absence of iron buffering in the chloroplast, cells activate iron efflux and/or repress iron influx to limit the amount of iron in the cell. In flowers, Perls/DAB staining has revealed a major sink for Fe in the anthers. In particular, developing pollen grains accumulate detectable amounts of Fe in small-size intracellular bodies that aggregate around the vegetative nucleus at the binuclear stage and that were identified as amyloplasts. In conclusion, using the Perls/DAB procedure combined to selected mutant genotypes, this study has established a reliable atlas of Fe distribution in the main Arabidopsis organs, proving and refining long-assumed intracellular locations and uncovering new ones. This iron map of Arabidopsis will serve as a basis for future studies of possible actors of iron movement in plant tissues and cell compartments.

  10. Identification and analysis of novel genes involved in gravitropism of Arabidopsis thaliana.

    Science.gov (United States)

    Morita, Miyo T.; Tasaka, Masao; Masatoshi Taniguchi, .

    2012-07-01

    Gravitropism is a continuous control with regard to the orientation and juxtaposition of the various parts of the plant body in response to gravity. In higher plants, the relative directional change of gravity is mainly suscepted in specialized cells called statocytes, followed by signal conversion from physical information into physiological information within the statocytes. We have studied the early process of shoot gravitropism, gravity sensing and signaling process, mainly by molecular genetic approach. In Arabidopsis shoot, statocytes are the endodermal cells. sgr1/scarcrow (scr) and sgr7/short-root (shr) mutants fail to form the endodermis and to respond to gravity in their inflorescence stems. Since both SGR1/SCR and SGR7/SHR are transcriptional factors, at least a subset of their downstream genes can be expected to be involved in gravitropism. In addition, eal1 (endodermal-amyloplast less 1), which exhibits no gravitropism in inflorescence stem but retains ability to form endodermis, is a hypomorphic allele of sgr7/shr. Take advantage of these mutants, we performed DNA microarray analysis and compared gene expression profiles between wild type and the mutants. We found that approx. 40 genes were commonly down-regulated in these mutants and termed them DGE (DOWN-REGULATED GENE IN EAL1) genes. DGE1 has sequence similarity to Oryza sativa LAZY1 that is involved in shoot gravitropism of rice. DGE2 has a short region homologous to DGE1. DTL (DGE TWO-LIKE}) that has 54% identity to DGE2 is found in Arabidopsis genome. All three genes are conserved in angiosperm but have no known functional domains or motifs. We analyzed T-DNA insertion for these genes in single or multiple combinations. In dge1 dge2 dtl triple mutant, gravitropic response of shoot, hypocotyl and root dramatically reduced. Now we are carrying out further physiological and molecular genetic analysis of the triple mutant.

  11. Differentiation of nodules of Glycine max : Ultrastructural studies of plant cells and bacteroids.

    Science.gov (United States)

    Werner, D; Mörschel, E

    1978-01-01

    Plants of Glycine max var. Caloria, infected as 14 d old seedlings with a defined titre of Rhizobium japonicum 3Il b85 in a 10 min inoculation test, develop a sharp maximum of nitrogenase activity between 17 and 25 d after infection. This maximum (14±3 nmol C2H4 h(-1) mg nodule fresh weight(-1)), expressed as per mg nodule or per plant is followed by a 15 d period of reduced nitrogen fixation (20-30% of peak activity). 11 d after infection the first bacteroids develop as single cells inside infection vacuoles in the plant cells, close to the cell wall and infection threads. As a cytological marker for peak multiplication of bacteroids and for peak N2-fixation a few days later the association of a special type of nodule mitochondria with amyloplasts is described. 20 d after inoculation, more than 80% of the volume of infected plant cells is occupied by infection vacuoles, mostly containing only one bacteroid. The storage of poly-β-hydroxybutyrate starts to accumulate at both ends of the bacteroids. Non infected plant cells are squeezed between infected cells (25d), with infection vacuoles containing now more than two (up to five) bacteroids per section. Bacteroid development including a membrane envelope is also observed in the intercellular space between plant cells. 35 d after infection, more than 50% of the bacteroid volume is occupied by poly-β-hydroxybutyrate. The ultrastructural differentiation is discussed in relation to some enzymatic data in bacteroids and plant cell cytoplasm during nodule development.

  12. Development of Gravity Sensitive Plant Cells (Ceratodon) in Microgravity

    Science.gov (United States)

    Sack, Fred D.

    1999-01-01

    Protonemata of the moss Ceratodon are tip-growing cells that grow up in the dark. This cell type is unique compared to cells in almost any other organism, since the growth of the plant cell itself is completely oriented by gravity. Thus, both the processes of gravity sensing and the gravity response occur in the same cell. Gravity sensing appears to rely upon amyloplasts (starch-filled plastids) that sediment. This sedimentation occurs in specific zones and plastid zonation is complex with respect to plastid morphology, distribution, and gravity. Microtubules restrict the extent of plastid sedimentation (i.e., they are load-bearing). Light also is important since apical cells have a phytochrome-based positive phototropism, light quality influences plastid zonation and sedimentation (photomorphogenesis), and red light suppresses gravitropism at higher but not lower light intensities. Many of these processes were examined in a 16 day spaceflight experiment, "SPM-A" space moss" or "SPAM)) on STS-87 that landed in December, 1997. The work described here involves the definition of a second flight experiment that builds upon the data and questions arising from STS-87. Effort was directed towards further definition of an experiment for the Shuttle (dubbed "SOS" for "Son of SPAM"). Our current target is STS 107 that is scheduled to fly in January 2001. This definition addressed two goals of the STS107 experiment. The goals of the current experiment were to determine whether the cytoskeleton plays a role in maintaining and generating an apical (non-random) plastid distribution in microgravity and to determine the development and extent of clockwise spiral tip-growth in microgravity.

  13. Antisense inhibition of the plastidial glucose-6-phosphate/phosphate translocator in Vicia seeds shifts cellular differentiation and promotes protein storage.

    Science.gov (United States)

    Rolletschek, Hardy; Nguyen, Thuy H; Häusler, Rainer E; Rutten, Twan; Göbel, Cornelia; Feussner, Ivo; Radchuk, Ruslana; Tewes, Annegret; Claus, Bernhard; Klukas, Christian; Linemann, Ute; Weber, Hans; Wobus, Ulrich; Borisjuk, Ljudmilla

    2007-08-01

    The glucose-6-phosphate/phosphate translocator (GPT) acts as an importer of carbon into the plastid. Despite the potential importance of GPT for storage in crop seeds, its regulatory role in biosynthetic pathways that are active during seed development is poorly understood. We have isolated GPT1 from Vicia narbonensis and studied its role in seed development using a transgenic approach based on the seed-specific legumin promoter LeB4. GPT1 is highly expressed in vegetative sink tissues, flowers and young seeds. In the embryo, localized upregulation of GPT1 at the onset of storage coincides with the onset of starch accumulation. Embryos of transgenic plants expressing antisense GPT1 showed a significant reduction (up to 55%) in the specific transport rate of glucose-6-phosphate as determined using proteoliposomes prepared from embryos. Furthermore, amyloplasts developed later and were smaller in size, while the expression of genes encoding plastid-specific translocators and proteins involved in starch biosynthesis was decreased. Metabolite analysis and stable isotope labelling demonstrated that starch biosynthesis was also reduced, although storage protein biosynthesis increased. This metabolic shift was characterized by upregulation of genes related to nitrogen uptake and protein storage, morphological variation of the protein-storing vacuoles, and a crude protein content of mature seeds of transgenics that was up to 30% higher than in wild-type. These findings provide evidence that (1) the prevailing level of GPT1 abundance/activity is rate-limiting for the synthesis of starch in developing seeds, (2) GPT1 exerts a controlling function on assimilate partitioning into storage protein, and (3) GPT1 is essential for the differentiation of embryonic plastids and seed maturation.

  14. Integration of orientation, clinorotation, and sensitivity in the graviresponse

    Science.gov (United States)

    Hasenstein, Karl H.; John, Susan

    Gravitropism describes the response of plants to some acceleration and typically involves amy-loplast displacement. Despite numerous studies, opinions diverge on the perception threshold and persistence of the stimulus. Short-term reorientation in the gravity field and superim-posed mechanostimulation (clinorotation) has the potential to reveal the duration (half-life) of mechanostimulation or memory persistence. Although clinorotation is commonly used to compensate the effect of continuous gravity stimulation, it adds long-term mechanostimulation to short-term reorientation. The constantly changing gravity vector is likely to interfere with curvature and root development. Especially sensitive are columella cells and entire layers have been shown to undergo programmed cell death upon clinorotation. It is unknown to what extent this response depends on the onset, speed, or duration of clinorotation. To determine the susceptibility of the graviresponse on clinorotation, we studied the effects of the rate (0.5 to 5 rpm) of rotation of reoriented flax roots (placed horizontally for 5, 10, or 15 min). Seedlings were kept in the dark, clinorotated either parallel or perpendicular to the root axis and imaged after each rotation by an infrared video camera. Horizontal clinorotation did not affect root growth rate (0.78±0.05 mm/h) but vertical clinorotation reduced root growth by more than 10%. The rate of clinorotation did not affect growth for either condition. However, maximal curvature for vertical clinorotation decreased with increasing rate of rotation and produced straight roots at 5 rpm. Horizontal clinorotation increased curvature with increasing reorienta-tion time and resulted in curvature that increased with the rotation rate. Thus, clinorotation changes the graviresponse but introduces secondary effects that depend on rate and direction of rotation.

  15. Characterization of root agravitropism induced by genetic, chemical, and developmental constraints

    International Nuclear Information System (INIS)

    Moore, R.; Fondren, W.M.; Marcum, H.

    1987-01-01

    The patterns and rates of organelle redistribution in columella (i.e., putative statocyte) cells of agravitropic agt mutants of Zea mays are not significantly different from those of columella cells in graviresponsive roots. Graviresponsive roots of Z. mays are characterized by a strongly polar movement of 45 Ca 2+ across the root tip from the upper to the lower side. Horizontally-oriented roots of agt mutants exhibit only a minimal polar transport of 45 Ca 2+ . Exogenously-induced asymmetries of Ca result in curvature of agt roots toward the Ca source. A similar curvature can be induced by a Ca asymmetry in normally nongraviresponsive (i.e., lateral) roots of Phaseolus vulgaris. Similarly, root curvature can be induced by placing the roots perpendicular to an electric field. This electrotropism increase with (1) currents between 8-35 mA, and (2) time between 1-9 hr when the current is constant. Electrotropism is reduced significantly by treating roots with triiodobenzoic acid (TIBA), an inhibitor of auxin transport. These results suggest that (1) if graviperception occurs via the sedimentation of amyloplasts in columella cells, then nongraviresponsive roots apparently sense gravity as do graviresponsive roots, (2) exogenously induced asymmetries of a gravitropic effector (i.e., Ca) can induce curvature of normally nongraviresponsive roots, (3) the gravity-induced downward movement of exogenously-applied 45 Ca 2+ across tips of graviresponsive roots does not occur in nongraviresponsive roots, (4) placing roots in an electrical field (i.e., one favoring the movement of ions such as Ca 2+ ) induces root curvature and (5) electrically-induced curvature is apparently dependent on auxin transport. These result are discussed relative to a model to account for the lack of graviresponsiveness by these roots

  16. The cytoskeleton and gravitropism in higher plants

    Science.gov (United States)

    Blancaflor, Elison B.

    2002-01-01

    The cellular and molecular mechanisms underlying the gravitropic response of plants have continued to elude plant biologists despite more than a century of research. Lately there has been increased attention on the role of the cytoskeleton in plant gravitropism, but several controversies and major gaps in our understanding of cytoskeletal involvement in gravitropism remain. A major question in the study of plant gravitropism is how the cytoskeleton mediates early sensing and signal transduction events in plants. Much has been made of the actin cytoskeleton as the cellular structure that sedimenting amyloplasts impinge upon to trigger the downstream signaling events leading to the bending response. There is also strong molecular and biochemical evidence that the transport of auxin, an important player in gravitropism, is regulated by actin. Organizational changes in microtubules during the growth response phase of gravitropism have also been well documented, but the significance of such reorientations in controlling differential cellular growth is unclear. Studies employing pharmacological approaches to dissect cytoskeletal involvement in gravitropism have led to conflicting results and therefore need to be interpreted with caution. Despite the current controversies, the revolutionary advances in molecular, biochemical, and cell biological techniques have opened up several possibilities for further research into this difficult area. The myriad proteins associated with the plant cytoskeleton that are being rapidly characterized provide a rich assortment of candidate regulators that could be targets of the gravity signal transduction chain. Cytoskeletal and ion imaging in real time combined with mutant analysis promises to provide a fresh start into this controversial area of research.

  17. Lack of fructose-1,6-bisphosphatase in a range of higher plants that store starch.

    Science.gov (United States)

    Entwistle, G; ap Rees, T A

    1990-01-01

    The aim of this work was to discover whether fructose-1,6-bisphosphatase (FBPase) is present in higher-plant cells that synthesize storage starch. The following were examined: suspension cultures of soybean (Glycine max), tubers of potato (Solanum tuberosum), florets of cauliflower (Brassica oleracea), developing endosperm of maize and of sweet corn (Zea mays), roots of pea (Pisum sativum), and the developing embryos of round and wrinkled varieties of pea. Unfractionated extracts of each tissue readily converted fructose 1,6-bisphosphate to fructose 6-phosphate in assays for both plastidic and cytosolic FBPase. These conversions were not inhibited by 20 microM-fructose 2,6-bisphosphate. Except in extracts of pea embryos and sweet-corn endosperm, treatment with affinity-purified antibodies to pyrophosphate: fructose-6-phosphate 1-phosphotransferase reduced the above fructose 6-phosphate production to the rate found with boiled extracts. The antibody-resistant activity from sweet corn was slight. In immunoblot analyses, antibody to plastidic FBPase did not react positively with any protein in extracts of soybean cells, potato tuber, cauliflower florets, maize endosperm and pea roots. Positive reactions were found for extracts of embryos of both round and wrinkled varieties of peas and endosperm of sweet corn. For pea embryos, but not for sweet-corn endosperm, the Mr of the recognized protein corresponded to that of plastidic FBPase. It is argued that soybean cells, potato tuber, cauliflower florets, maize (var. White Horse Tooth) endosperm and pea roots lack significant activity of plastidic FBPase, but that this enzyme is present in developing embryos of pea. The data for sweet corn (var. Golden Bantam) are not decisive. It is also argued that, where FBPase is absent, carbon for starch synthesis does not enter the amyloplast as triose phosphate. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. PMID:2173563

  18. Changes in Lipid Peroxidation and Lipolytic and Free-Radical Scavenging Enzyme Activities during Aging and Sprouting of Potato (Solanum tuberosum) Seed-Tubers.

    Science.gov (United States)

    Kumar, GNM.; Knowles, N. R.

    1993-05-01

    Previous research has shown that cell membranes of potato (Solanum tuberosum L. cv Russet Burbank) seed-tubers lose integrity between 7 and 26 months of storage (4[deg]C, 95% relative humidity), and this loss coincides with a significant decrease in growth potential. The age-induced decline in membrane integrity is apparently due to increased peroxidative damage of membrane lipids. Malondialdehyde (MDA) and ethane concentrations (sensitive markers of lipid peroxidation and membrane damage) increased in seed-tuber tissues with advancing age. Moreover, in vivo ethane production from discs of cortex tissue from 13- and 25-month-old seed-tubers was 87% greater (on average) than that from discs from 1-month-old tubers. Calcium suppressed ethane production from all ages of tissue discs, and the effect was concentration dependent. Linoleic acid enhanced ethane production from 5- and 17-month-old tubers by 61 and 228%, respectively, suggesting that older tissue may contain a higher free-radical (FR) titer and/or lower free polyunsaturated fatty acid content. In addition, throughout plant establishment, the internal ethane concentration of older seed-tubers was 54% higher than that of younger seed-tubers. MDA concentration of tuber tissue declined by about 65% during the initial 7 months of storage and then increased 267% as tuber age advanced to 30 months. The age-induced trend in tuber reducing sugar concentration was similar to that of MDA, and the two were linearly correlated. The age-dependent increase in reducing sugars may thus reflect peroxidative degeneration of the amyloplast membrane, leading to increased starch hydrolysis. Compared with 5-month-old seed tubers, 17- and 29-month-old seed-tubers had significantly higher levels of lipofuscin-like fluorescent compounds (FCs), which are produced when MDA reacts with free amino acids. Age-dependent increases in MDA, ethane, and FCs were not associated with higher activities of phospholipase and lipoxygenase in tissue

  19. Water mediated alterations in gravity signal transform phytofilertation capability in hydroponic plants

    Science.gov (United States)

    Singh, Yogranjan; Singh Marabi, Rakesh; Satpute, Gyanesh Kumar; Mishra, Stuti

    2012-07-01

    signal is generated by the sedimentation of the amyloplasts. This induces a signal transduction pathway that promotes an auxin gradient across the root. The proteinogenic amino acid proline functions as a radical scavenger, electron sink, stabilizer of macromolecules, cell wall component and a metal chelation compound. In order to have most competent option for phytofilteration, the natural biodiversity out of aquatic ecosystem should be better studied. Screening of plants that produce natural chemicals whose structures are similar to the xenobiotic compounds should be the first step of any phytoremediation process. An experimental hydroponic-phytofilteration system with real effluent must give pragmatic information on the real detoxification capacity of the plants and allow determining the appropriate design and size of the future constructed wetland system to clean up the contaminated wastewater to reduce negative impact of eutrophication.

  20. The potential of two Salix genotypes for radionuclide/heavy metal accumulation. A case study of Rovinari ash pit (Gorj District, Romania)

    Science.gov (United States)

    Hernea, Cornelia; Neţoiu, Constantin; Corneanu, Gabriel; Crăciun, Constantin; Corneanu, Mihaela; Cojocaru, Luminiţa; Rovena Lăcătuşu, Anca; Popescu, Ion

    2014-05-01

    heavy metals and radionuclides, in comparison with Salix alba. In seedlings developed on ash waste dump, in leaf cells, the fine blocks of heterochromatin are dispersed in nucleus. The chloroplast with well developed grana and numerous plastoglobuls, are in active synthesis (being present 2 - 4 starch grains), some chloroplasts being transformed in amyloplast. In the mitochondria matrix, are present ferritin aggregates, with role in cell detoxification processes.

  1. Himatanthus lancifolius (Müll. Arg. Woodson, Apocynaceae: estudo farmacobotânico de uma planta medicinal da Farmacopeia brasileira 1ª edição Himatanthus lancifolius (Müll. Arg. Woodson, Apocynaceae: morpho-anatomical study of a medicinal plant described in the Brazilian Pharmacopoeia 1st edition

    Directory of Open Access Journals (Sweden)

    Leopoldo C. Baratto

    2010-11-01

    Full Text Available Himatanthus lancifolius (Müll. Arg. Woodson é um arbusto nativo do Brasil, latescente, popularmente conhecido como agoniada e utilizado principalmente para distúrbios menstruais. O presente trabalho teve como objetivo caracterizar morfoanatomicamente a folha, o caule e a casca caulinar dessa planta medicinal, a fim de contribuir para o controle de qualidade e a autenticidade dessa espécie. O material vegetal foi fixado e submetido às microtécnicas usuais. A folha é simples, glabra e obovado-lanceolada. A epiderme é uniestratificada, revestida por cutícula estriada e possui estômatos anisocíticos na face abaxial. O mesofilo é dorsiventral. A nervura central é biconvexa e o pecíolo é circular, ambos apresentando feixes vasculares bicolaterais. Laticíferos, amiloplastos e idioblastos fenólicos estão presentes no parênquima fundamental da nervura central e do pecíolo. O sistema vascular do caule é tipicamente bicolateral. Laticíferos e idioblastos fenólicos ocorrem no córtex, no floema e na medula. Esses caracteres morfoanatômicos, em conjunto, podem ser utilizados como parâmetros para o controle de qualidade dessa espécie.Himatanthus lancifolius (Müll. Arg. Woodson is a Brazilian native shrub, laticiferous, popularly known as "agoniada" and it is mainly used for uterine disorders. The present work aimed to study the leaf, stem and stem bark morpho-anatomy of this medicinal plant, in order to contribute to its quality control and identification. The plant material was fixed and submitted to standard microtechniques. The leaf is simple, glabrous and obovate-lanceolate. The epidermis is uniseriate, coated with striated cuticle and it has anysocitic stomata on the abaxial surface. The mesophyll is dorsiventral. The midrib is biconvex and the petiole is circular, both presenting bicollateral vascular bundles. Laticiferous ducts, amyloplasts and phenolic idioblasts are found in ground parenchyma of the midrib and petiole. The

  2. ARG1 and ARL2 contribute to gravity signal transduction in the statocytes of Arabidopsis thaliana roots and hypocotyls

    Science.gov (United States)

    Masson, Patrick; Harrison, Benjamin; Stanga, John; Otegui, Marisa; Sedbrook, John

    those of the single mutants. We used this observation to design a genetic screen for the identification of new loci that contribute to the pgm gravity-signaling pathway. Two genetic enhancers of arg1-2 were identified this way, called mar1-1 and mar2-1. These mutations were shown to affect components of the protein-import complex found in the outer membrane of plastids. Interestingly, the columellar amyloplasts of arg1-2 mar2-1 mutant roots display wild-type ultra-structure, accumulate starch and sediment at wild-type rates upon gravistimulation. We conclude that the plastid outer envelope may contribute directly to gravity signal transduction within the statocytes.

  3. Ultrastructural features of Mimulus aurantiacus (Scrophulariaceae pollen tubes in vivo

    Directory of Open Access Journals (Sweden)

    Nuran Ekici

    2009-03-01

    Full Text Available The aim of this study is to give information on ultrastructure of in vivo pollen tubes of Mimulus aurantiacus which were collected from the Botanical Garden of the University of California at Berkeley. Materials were prepared according to electron microscopy methods and examined under Zeiss electron microscope. Four zones were examined in the pollen tubes of Mimulus aurantiacus. APICAL ZONE: Mitochondria, smooth endoplasmic reticulum, rough endoplasmic reticulum, dictyosomes and secretory vesicles were observed. SUBAPICAL ZONE: This area contained abundant rough endoplasmic reticulum and occasionally some smooth endoplasmic reticulum. The polysomes, mitochondria, proplastids that contain starch, small vacuoles and a few lipid bodies were detected. NUCLEAR ZONE: Both generative and vegetative cell nuclei lie in this zone. The vegetative cell nucleus was large and long. Rough endoplasmic reticulum, mitochondria, ribosomes, dictyosomes, and amyloplasts that are rich of starch were observed. VACUOLATION AND PLUG FORMATION ZONE: Cytoplasm of the tubes was full of large vacuoles. Few organelles such as mitochondria, dictyosome and rough endoplasmic reticulum were detected along their periphery.O objetivo deste estudo é informar sobre a ultraestrutura de tubos de pólen de Mimulus aurantiacus in vivo coletados no "Botanical Garden" da Universidade da Califórnia em Berkeley. O material foi preparado de acordo com os métodos de microscopia eletrônica e examinado em microscópio eletrônico Zeiss. Quatro zonas dos tubos de pólen de Mimulus aurantiacus foram examinadas. ZONA APICAL: foram observados mitocôndrias, retículo endoplasmático liso; retículo endoplasmático rugoso, dictiossomos e vesículas secretoras. ZONA SUBAPICAL: esta área continha retículo endoplasmático rugoso em abundância e, ocasionalmente, algum retículo endoplasmático liso. Foram detectados polissomos, mitocôndrias, proplastídeos que contêm amido, pequenos vacúolos e

  4. Pharmacobotanic characterization of young stems and stem barks of Rauvolfia sellowii Müll. Arg., Apocynaceae

    Directory of Open Access Journals (Sweden)

    Leopoldo Clemente Baratto

    2010-09-01

    Full Text Available Rauvolfia sellowii Müll. Arg. (Apocynaceae, a Brazilian native tree rich in indole alkaloids, is known as "pau-pra-tudo" and popularly used as hypocholesterolemic, hypoglycemic and antihypertensive. The aim of this work was to study the anatomy of the young stems and stem barks of this medicinal plant, in order to contribute to the identification of the species as a drug. The plant material was fixed and prepared according to standard microtechniques. The young stems have remaining epidermis, but a suberified peridermis is evident. The phellogen is located in the cortical region, forming suber externally. Underneath the phellogen, lies the phelloderm and collenchymatic region. In the cortex, there are numerous laticifers and some fibers. There is an incomplete sclerenchymatic sheath, consisting of several groups of fibers and stone cells. The stem has internal phloem ordered as isolated groups side by side. Numerous laticifers, calcium oxalate crystals, idioblasts and amyloplasts are found in the cortex, phloem, xylem and pith. The stem bark has many layers of suber and cortical parenchyma, a sheath composed of fibers and stone cells totally lignified, and external phloem. These anatomical characteristic, taken together, can be used as quality control parameters for this species.Rauvolfia sellowii Müll. Arg. (Apocynaceae, uma árvore nativa brasileira rica em alcaloides indólicos, é conhecida como "pau-pra-tudo" e utilizada popularmente como hipocolesterolêmica, hipoglicêmica e anti-hipertensiva. O presente trabalho teve como objetivo caracterizar anatomicamente o caule jovem e a casca caulinar dessa planta medicinal, a fim de contribuir para a identificação e autenticidade da droga. O material vegetal foi fixado e submetido às microtécnicas usuais. O caule jovem possui epiderme remanescente, porém uma periderme suberificada é observada. O felogênio instala-se na região cortical, formando súber externamente. Subjacentes ao felog