Zhang, Hao; Li, Hongwei; Yuan, Liming; Wang, Zhiqin; Yang, Jianchang; Zhang, Jianhua
This study tested the hypothesis that a post-anthesis moderate soil drying can improve grain filling through regulating the key enzymes in the sucrose-to-starch pathway in the grains of rice (Oryza sativa L.). Two rice cultivars were field grown and two irrigation regimes, alternate wetting and moderate soil drying (WMD) and conventional irrigation (CI, continuously flooded), were imposed during the grain-filling period. The grain-filling rate and activities of four key enzymes in sucrose-to-starch conversion, sucrose synthase (SuSase), adenosine diphosphate-glucose pyrophosphorylase (AGPase), starch synthase (StSase), and starch branching enzyme (SBE), showed no significant difference between WMD and CI regimes for the earlier flowering superior spikelets. However, they were significantly enhanced by the WMD for the later flowering inferior spikelets. The activities of both soluble and insoluble acid invertase in the grains were little affected by the WMD. The two cultivars showed the same tendencies. The activities of SuSase, AGPase, StSase, and SBE in grains were very significantly correlated with the grain-filling rate. The abscisic acid (ABA) concentration in inferior spikelets was remarkably increased in the WMD and very significantly correlated with activities of SuSase, AGPase, StSase, and SBE. Application of ABA on plants under CI produced similar results to those seen in plants receiving WMD. Applying fluridone, an indirect inhibitor of ABA synthesis, produced the opposite effect. The results suggest that post-anthesis WMD could enhance sink strength by regulating the key enzymes involved, and consequently, increase the grain-filling rate and grain weight of inferior spikelets. ABA plays an important role in this process.
Full Text Available The changes in activities of key enzymes involved in sucrose-to-starch conversion and concentrations of hormones in superior and inferior spikelets of super rice were investigated and their association with grain filling was analyzed. Four super rice cultivars, Liangyoupeijiu, IIyou 084, Huaidao 9 and Wujing 15, and two high-yielding and elite check cultivars, Shanyou 63 and Yangfujing 8, were used. The activities of sucrose synthase (SuSase, adenosine diphosphoglucose pyrophosphorylase (AGPase, starch synthase (StSase and starch branching enzyme (SBE, and the concentrations of zeatin + zeatin riboside (Z + ZR, indole-3-acetic acid (IAA and abscisic acid (ABA in superior and inferior spikelets were determined during the grain filling period and their relationships with grain filling rate were analyzed. Maximum grain filling rate, the time reaching the maximum grain-filling rate, mean grain filling rate and brown rice weight for superior spikelets showed a slight difference between the super and check rice cultivars, but were significantly lower in the super rice than in the check rice for inferior spikelets. Changes of enzyme activities and hormone concentrations in grains exhibited single peak curves during the grain filling period. The peak values and the mean activities of SuSase, AGPase, StSase and SBE were lower in inferior spikelets than in superior ones, as well as the peak values and the mean concentrations of Z + ZR and IAA. However, the peak value and the mean concentration of ABA were significantly higher in inferior spikelets than in superior ones and greater in the super rice than in the check rice. The grain filling rate was positively and significantly correlated with the activities of SuSase, AGPase and StSase and the concentrations of Z + ZR and IAA. The results suggested that the low activities of SuSase, AGPase and StSase and the low concentrations of Z + ZR and IAA might be important physiological reasons for the slow grain
Saripalli, Gautam; Gupta, Pushpendra Kumar
AGPase, a key enzyme of starch biosynthetic pathway, has a significant role in crop productivity. Thermotolerant variants of AGPase in cereals may be used for developing cultivars, which may enhance productivity under heat stress. Improvement of crop productivity has always been the major goal of plant breeders to meet the global demand for food. However, crop productivity itself is influenced in a large measure by a number of abiotic stresses including heat, which causes major losses in crop productivity. In cereals, crop productivity in terms of grain yield mainly depends upon the seed starch content so that starch biosynthesis and the enzymes involved in this process have been a major area of investigation for plant physiologists and plant breeders alike. Considerable work has been done on AGPase and its role in crop productivity, particularly under heat stress, because this enzyme is one of the major enzymes, which catalyses the rate-limiting first committed key enzymatic step of starch biosynthesis. Keeping the above in view, this review focuses on the basic features of AGPase including its structure, regulatory mechanisms involving allosteric regulators, its sub-cellular localization and its genetics. Major emphasis, however, has been laid on the genetics of AGPases and its manipulation for developing high yielding cultivars that will have comparable productivity under heat stress. Some important thermotolerant variants of AGPase, which mainly involve specific amino acid substitutions, have been highlighted, and the prospects of using these thermotolerant variants of AGPase in developing cultivars for heat prone areas have been discussed. The review also includes a brief account on transgenics for AGPase, which have been developed for basic studies and crop improvement.
Full Text Available ADP-glucose pyrophosphorylase (AGPase is the first rate limiting enzyme of starch biosynthesis pathway and has been exploited as the target for greater starch yield in several plants. The structure-function analysis and substrate binding specificity of AGPase have provided enormous potential for understanding the role of specific amino acid or motifs responsible for allosteric regulation and catalytic mechanisms, which facilitate the engineering of AGPases. We report the three-dimensional structure, substrate, and inhibitor binding specificity of AGPase small subunit from different monocot and dicot crop plants. Both monocot and dicot subunits were found to exploit similar interactions with the substrate and inhibitor molecule as in the case of their closest homologue potato tuber AGPase small subunit. Comparative sequence and structural analysis followed by molecular docking and electrostatic surface potential analysis reveal that rearrangements of secondary structure elements, substrate, and inhibitor binding residues are strongly conserved and follow common folding pattern and orientation within monocot and dicot displaying a similar mode of allosteric regulation and catalytic mechanism. The results from this study along with site-directed mutagenesis complemented by molecular dynamics simulation will shed more light on increasing the starch content of crop plants to ensure the food security worldwide.
Corbi, Jonathan; Dutheil, Julien Y; Damerval, Catherine; Tenaillon, Maud I; Manicacci, Domenica
ADP-glucose pyrophosphorylase (AGPase) is a key enzyme of starch biosynthesis. In the green plant lineage, it is composed of two large (LSU) and two small (SSU) sub-units encoded by paralogous genes, as a consequence of several rounds of duplication. First, our aim was to detect specific patterns of molecular evolution following duplication events and the divergence between monocotyledons and dicotyledons. Secondly, we investigated coevolution between amino acids both within and between sub-units. A phylogeny of each AGPase sub-unit was built using all gymnosperm and angiosperm sequences available in databases. Accelerated evolution along specific branches was tested using the ratio of the non-synonymous to the synonymous substitution rate. Coevolution between amino acids was investigated taking into account compensatory changes between co-substitutions. We showed that SSU paralogues evolved under high functional constraints during angiosperm radiation, with a significant level of coevolution between amino acids that participate in SSU major functions. In contrast, in the LSU paralogues, we identified residues under positive selection (1) following the first LSU duplication that gave rise to two paralogues mainly expressed in angiosperm source and sink tissues, respectively; and (2) following the emergence of grass-specific paralogues expressed in the endosperm. Finally, we found coevolution between residues that belong to the interaction domains of both sub-units. Our results support the view that coevolution among amino acid residues, especially those lying in the interaction domain of each sub-unit, played an important role in AGPase evolution. First, within SSU, coevolution allowed compensating mutations in a highly constrained context. Secondly, the LSU paralogues probably acquired tissue-specific expression and regulatory properties via the coevolution between sub-unit interacting domains. Finally, the pattern we observed during LSU evolution is consistent
Conclusions: This work reveals the possible number of AGPase enzyme isoforms and their molecular levels in banana. Molecular markers could be designed from SNPs present in these banana accessions. This information could be useful for the development of SNP-based molecular markers for Musa germplasm, and alteration of the allosteric properties of AGPase to increase the starch content and manipulate the starch quality of banana fruits.
Zhou, Yu-Xi; Chen, Yu-Xiang; Tao, Xiang; Cheng, Xiao-Jie; Wang, Hai-Yan
Sweet potato [Ipomoea batatas (L.) Lam.], the world's seventh most important food crop, is also a major industrial raw material for starch and ethanol production. In the plant starch biosynthesis pathway, ADP-glucose pyrophosphorylase (AGPase) catalyzes the first, rate-limiting step and plays a pivotal role in regulating this process. In spite of the importance of sweet potato as a starch source, only a few studies have focused on the molecular aspects of starch biosynthesis in sweet potato and almost no intensive research has been carried out on the AGPase gene family in this species. In this study, cDNAs encoding two small subunits (SSs) and four large subunits (LSs) of AGPase isoforms were cloned from sweet potato and the genomic organizations of the corresponding AGPase genes were elucidated. Expression pattern analysis revealed that the two SSs were constitutively expressed, whereas the four LSs displayed differential expression patterns in various tissues and at different developmental stages. Co-expression of SSs with different LSs in Escherichia coli yielded eight heterotetramers showing different catalytic activities. Interactions between different SSs and LSs were confirmed by a yeast two-hybrid experiment. Our findings provide comprehensive information about AGPase gene sequences, structures, expression profiles, and subunit interactions in sweet potato. The results can serve as a foundation for elucidation of molecular mechanisms of starch synthesis in tuberous roots, and should contribute to future regulation of starch biosynthesis to improve sweet potato starch yield.
Choix, Francisco J; Bashan, Yoav; Mendoza, Alberto; de-Bashan, Luz E
ADP-glucose pyrophosphorylase (AGPase) regulates starch biosynthesis in higher plants and microalgae. This study measured the effect of the bacterium Azospirillum brasilense on AGPase activity in the freshwater microalga Chlorella vulgaris and formation of starch. This was done by immobilizing both microorganisms in alginate beads, either replete with or deprived of nitrogen or phosphorus and all under heterotrophic conditions, using d-glucose or Na-acetate as the carbon source. AGPase activity during the first 72h of incubation was higher in C. vulgaris when immobilized with A. brasilense. This happened simultaneously with higher starch accumulation and higher carbon uptake by the microalgae. Either carbon source had similar effects on enzyme activity and starch accumulation. Starvation either by N or P had the same pattern on AGPase activity and starch accumulation. Under replete conditions, the population of C. vulgaris immobilized alone was higher than when immobilized together, but under starvation conditions A. brasilense induced a larger population of C. vulgaris. In summary, adding A. brasilense enhanced AGPase activity, starch formation, and mitigation of stress in C. vulgaris. Copyright © 2014 Elsevier B.V. All rights reserved.
The current concept for starch biosynthesis in plants is that amylopectin, the major fraction of starch, is synthesised by the concerted actions of ADP-Glc pyrophosphorylase (AGPase), soluble starch synthase (SS), starch-branching enzyme (BE), and starch-debranching enzyme (DBE). We have isolated a cDNA clone of.
Convigton, E. D.; Roitsch, Thomas; Dernastia, M.
Roč. 63, č. 4 (2016), s. 757-762 ISSN 1318-0207 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : AGPase * carbohydrates * invertases * sucrose synthase * panel of enzyme activity assays * phytoplasma Subject RIV: EH - Ecology, Behaviour Impact factor: 0.983, year: 2016
Okita, Thomas W. [Washington State Univ., Pullman, WA (United States)
ADPglucose pyrophosphorylase (AGPase) and the plastidial starch phosphorylase1 (Pho1) are two regulatory enzymes whose catalytic activities are essential for starch granule synthesis. Conversion of the pre-starch granule to the mature form is dependent on AGPase, which produces ADPglucose, the substrate used by starch synthases. The catalytic activity of AGPase is controlled by small effector molecules and a prime goal of this project was to decipher the role of the two subunit types that comprise the heterotetrameric enzyme structure. Extensive genetic and biochemical studies showed that catalysis was contributed mainly by the small subunit although the large subunit was required for maximum activity. Both subunits were needed for allosteric regulatory properties. We had also demonstrated that the AGPase catalyzed reaction limits the amount of starch accumulation in developing rice seeds and that carbon flux into rice seed starch can be increased by expression of a cytoplasmic-localized, up-regulated bacterial AGPase enzyme form. Results of subsequent physiological and metabolite studies showed that the AGPase reaction is no longer limiting in the AGPase transgenic rice lines and that one or more downstream processes prevent further increases in starch biosynthesis. Further studies showed that over-production of ADPglucose dramatically alters the gene program during rice seed development. Although the expression of nearly all of the genes are down-regulated, levels of a starch binding domain containing protein (SBDCP) are elevated. This SBDCP was found to bind to and inhibit the catalytic activity of starch synthase III and, thereby preventing maximum starch synthesis from occurring. Surprisingly, repression of SBDCP elevated expression of starch synthase III resulting in increasing rice grain weight. A second phase of this project examined the structure-function of Pho1, the enzyme required during the initial phase of pre-starch granule formation and its
Nagai, Yasuko S; Sakulsingharoj, Chotipa; Edwards, Gerald E; Satoh, Hikaru; Greene, Thomas W; Blakeslee, Beth; Okita, Thomas W
We had previously demonstrated that expression of a cytoplasmic-localized ADPglucose pyrophosphorylase (AGPase) mutant gene from Escherichia coli in rice endosperm resulted in enhanced starch synthesis and, in turn, higher seed weights. In this study, the levels of the major primary carbon metabolites were assessed in wild type and four transgenic CS8 rice lines expressing 3- to 6-fold higher AGPase activity. Consistent with the increase in AGPase activity, all four transgenic CS8 lines showed elevated levels of ADPglucose (ADPglc) although the extent of increases in this metabolite was much higher than the extent of increases in starch as measured by seed weight. Surprisingly, the levels of several other key intermediates were significantly altered. Glucose 1-phosphate (Glc 1-P), a substrate of the AGPase reaction, as well as UDPglucose and Glc 6-P were also elevated to the same relative extent in the transgenic lines compared with the wild-type control. Analysis of metabolite ratios showed no significant differences between the wild type and transgenic lines, indicating that the reactions leading from sucrose metabolism to ADPglc formation were in near equilibrium. Moreover, glucose and fructose levels were also elevated in three transgenic lines that showed the largest differences in metabolites and seed weight over the wild type, suggesting the induction of invertase. Overall, the results indicate that the AGPase-catalyzed reaction is no longer limiting in the transgenic lines, and constraints on carbon flux into starch are downstream of ADPglc formation, resulting in an elevation of precursors upstream of ADPglc formation.
Cassava (Manihot esculenta Crantz) is a tropical crop grown for its starchy thickened roots, mainly by peasant farmers, in the tropics, for whom it is a staple food. There is an increasing demand for the use of cassava in processed food and feed products, and in the paper and textile industries amongst others. This thesis describes research on the cloning of the genes encoding ADP-glucose pyrophosphorylase small and large subunits (AGPase B and S, respectively)...
Seng, Shanshan, E-mail: firstname.lastname@example.org [Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Yuan Mingyuan Western Road 2#, Beijing 100193 (China); Wu, Jian [Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Yuan Mingyuan Western Road 2#, Beijing 100193 (China); Sui, Juanjuan [Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Yuan Mingyuan Western Road 2#, Beijing 100193 (China); College of Biology, Fuyang Normal College, Qinghe Western Road 100#, Fuyang 236037, Anhui (China); Wu, Chenyu; Zhong, Xionghui; Liu, Chen; Liu, Chao; Gong, Benhe; Zhang, Fengqin; He, Junna [Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Yuan Mingyuan Western Road 2#, Beijing 100193 (China); Yi, Mingfang, E-mail: email@example.com [Beijing Key Laboratory of Development and Quality Control of Ornamental Crops, Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Yuan Mingyuan Western Road 2#, Beijing 100193 (China)
Starch is the main storage compound in underground organs like corms. ADP-glucose pyrophosphorylase (AGPase) plays a key role in regulating starch biosynthesis in storage organs and is likely one of the most important determinant of sink strength. Here, we identify an AGPase gene (GhAGPS1) from gladiolus. The highest transcriptional levels of GhAGPS1 were observed in cormels and corms. Transformation of GhAGPS1 into Arabidopsis rescued the phenotype of aps1 mutant. Silencing GhAGPS1 in gladiolus corms by virus-induced gene silencing (VIGS) decreased the transcriptional levels of two genes and starch content. Transmission electron microscopy analyses of leaf and corm sections confirmed that starch biosynthesis was inhibited. Corm weight and cormel number reduced significantly in the silenced plants. Taken together, these results indicate that inhibiting the expression of AGPase gene could impair starch synthesis, which results in the lowered corm quality and cormel yield in gladiolus. -- Highlights: •Cormel quantity was reduced significantly in silenced Gladiolus plants. •Corm quality was declined significantly in silenced Gladiolus plants. •Starch synthesis was inhibited in silenced Gladiolus plants.
Jourda, Cyril; Cardi, Céline; Gibert, Olivier; Giraldo Toro, Andrès; Ricci, Julien; Mbéguié-A-Mbéguié, Didier; Yahiaoui, Nabila
Starch is the most widespread and abundant storage carbohydrate in plants. It is also a major feature of cultivated bananas as it accumulates to large amounts during banana fruit development before almost complete conversion to soluble sugars during ripening. Little is known about the structure of major gene families involved in banana starch metabolism and their evolution compared to other species. To identify genes involved in banana starch metabolism and investigate their evolutionary history, we analyzed six gene families playing a crucial role in plant starch biosynthesis and degradation: the ADP-glucose pyrophosphorylases (AGPases), starch synthases (SS), starch branching enzymes (SBE), debranching enzymes (DBE), α-amylases (AMY) and β-amylases (BAM). Using comparative genomics and phylogenetic approaches, these genes were classified into families and sub-families and orthology relationships with functional genes in Eudicots and in grasses were identified. In addition to known ancestral duplications shaping starch metabolism gene families, independent evolution in banana and grasses also occurred through lineage-specific whole genome duplications for specific sub-families of AGPase, SS, SBE, and BAM genes; and through gene-scale duplications for AMY genes. In particular, banana lineage duplications yielded a set of AGPase, SBE and BAM genes that were highly or specifically expressed in banana fruits. Gene expression analysis highlighted a complex transcriptional reprogramming of starch metabolism genes during ripening of banana fruits. A differential regulation of expression between banana gene duplicates was identified for SBE and BAM genes, suggesting that part of starch metabolism regulation in the fruit evolved in the banana lineage. PMID:27994606
Full Text Available Starch is the most widespread and abundant storage carbohydrate in plants. It is also a major feature of cultivated bananas as it accumulates to large amounts during banana fruit development before almost complete conversion to soluble sugars during ripening. Little is known about the structure of major gene families involved in banana starch metabolism and their evolution compared to other species. To identify genes involved in banana starch metabolism and investigate their evolutionary history, we analyzed six gene families playing a crucial role in plant starch biosynthesis and degradation: the ADP-glucose pyrophosphorylases (AGPases, starch synthases (SS, starch branching enzymes (SBE, debranching enzymes (DBE, -amylases (AMY and -amylases (BAM. Using comparative genomics and phylogenetic approaches, these genes were classified into families and sub-families and orthology relationships with functional genes in Eudicots and in grasses were identified. In addition to known ancestral duplications shaping starch metabolism gene families, independent evolution in banana and grasses also occurred through lineage-specific whole genome duplications for specific sub-families of AGPases, SS, SBE and BAM genes; and through gene-scale duplications for AMY genes. In particular, banana lineage duplications yielded a set of AGPases, SBE and BAM genes that were highly or specifically expressed in banana fruits. Gene expression analysis highlighted a complex transcriptional reprogramming of starch metabolism genes during ripening of banana fruits. A differential regulation of expression between banana gene duplicates was identified for SBE and BAM genes, suggesting that part of starch metabolism regulation in the fruit evolved in the banana lineage
Jourda, Cyril; Cardi, Céline; Gibert, Olivier; Giraldo Toro, Andrès; Ricci, Julien; Mbéguié-A-Mbéguié, Didier; Yahiaoui, Nabila
Starch is the most widespread and abundant storage carbohydrate in plants. It is also a major feature of cultivated bananas as it accumulates to large amounts during banana fruit development before almost complete conversion to soluble sugars during ripening. Little is known about the structure of major gene families involved in banana starch metabolism and their evolution compared to other species. To identify genes involved in banana starch metabolism and investigate their evolutionary history, we analyzed six gene families playing a crucial role in plant starch biosynthesis and degradation: the ADP-glucose pyrophosphorylases (AGPases), starch synthases (SS), starch branching enzymes (SBE), debranching enzymes (DBE), α-amylases (AMY) and β-amylases (BAM). Using comparative genomics and phylogenetic approaches, these genes were classified into families and sub-families and orthology relationships with functional genes in Eudicots and in grasses were identified. In addition to known ancestral duplications shaping starch metabolism gene families, independent evolution in banana and grasses also occurred through lineage-specific whole genome duplications for specific sub-families of AGPase, SS, SBE, and BAM genes; and through gene-scale duplications for AMY genes. In particular, banana lineage duplications yielded a set of AGPase, SBE and BAM genes that were highly or specifically expressed in banana fruits. Gene expression analysis highlighted a complex transcriptional reprogramming of starch metabolism genes during ripening of banana fruits. A differential regulation of expression between banana gene duplicates was identified for SBE and BAM genes, suggesting that part of starch metabolism regulation in the fruit evolved in the banana lineage.
Nardozza, Simona; Boldingh, Helen L; Osorio, Sonia; Höhne, Melanie; Wohlers, Mark; Gleave, Andrew P; MacRae, Elspeth A; Richardson, Annette C; Atkinson, Ross G; Sulpice, Ronan; Fernie, Alisdair R; Clearwater, Michael J
Tomato, melon, grape, peach, and strawberry primarily accumulate soluble sugars during fruit development. In contrast, kiwifruit (Actinidia Lindl. spp.) and banana store a large amount of starch that is released as soluble sugars only after the fruit has reached maturity. By integrating metabolites measured by gas chromatography-mass spectrometry, enzyme activities measured by a robot-based platform, and transcript data sets during fruit development of Actinidia deliciosa genotypes contrasting in starch concentration and size, this study identified the metabolic changes occurring during kiwifruit development, including the metabolic hallmarks of starch accumulation and turnover. At cell division, a rise in glucose (Glc) concentration was associated with neutral invertase (NI) activity, and the decline of both Glc and NI activity defined the transition to the cell expansion and starch accumulation phase. The high transcript levels of β-amylase 9 (BAM9) during cell division, prior to net starch accumulation, and the correlation between sucrose phosphate synthase (SPS) activity and sucrose suggest the occurrence of sucrose cycling and starch turnover. ADP-Glc pyrophosphorylase (AGPase) is identified as a key enzyme for starch accumulation in kiwifruit berries, as high-starch genotypes had 2- to 5-fold higher AGPase activity, which was maintained over a longer period of time and was also associated with enhanced and extended transcription of the AGPase large subunit 4 (APL4). The data also revealed that SPS and galactinol might affect kiwifruit starch accumulation, and suggest that phloem unloading into kiwifruit is symplastic. These results are relevant to the genetic improvement of quality traits such as sweetness and sugar/acid balance in a range of fruit species.
Tuncel, Aytug; Okita, Thomas W
Significant improvements in crop productivity are required to meet the nutritional requirements of a growing world population. This challenge is magnified by an increased demand for bioenergy as a means to mitigate carbon inputs into the environment. Starch is a major component of the harvestable organs of many crop plants, and various endeavors have been taken to improve the yields of starchy organs through the manipulation of starch synthesis. Substantial efforts have centered on the starch regulatory enzyme ADPglucose pyrophosphorylase (AGPase) due to its pivotal role in starch biosynthesis. These efforts include over-expression of this enzyme in cereal plants such as maize, rice and wheat as well as potato and cassava, as they supply the bulk of the staple food worldwide. In this perspective, we describe efforts to increase starch yields in cereal grains by first providing an introduction about the importance of source-sink relationship and the motives behind the efforts to alter starch biosynthesis and turnover in leaves. We then discuss the catalytic and regulatory properties of AGPase and the molecular approaches used to enhance starch synthesis by manipulation of this process during grain filling using seed-specific promoters. Several studies have demonstrated increases in starch content per seed using endosperm-specific promoters, but other studies have demonstrated an increase in seed number with only marginal impact on seed weight. Potential mechanisms that may be responsible for this paradoxical increase in seed number will also be discussed. Finally, we describe current efforts and future prospects to improve starch yield in cereals. These efforts include further enhancement of starch yield in rice by augmenting the process of ADPglucose transport into amyloplast as well as other enzymes involved in photoassimilate partitioning in seeds. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
A Robot-based platform to measure multiple enzyme activities in Arabidopsis using a set of cycling assays: comparison of changes of enzyme activities and transcript levels during diurnal cycles and in prolonged darkness.
Gibon, Yves; Blaesing, Oliver E; Hannemann, Jan; Carillo, Petronia; Höhne, Melanie; Hendriks, Janneke H M; Palacios, Natalia; Cross, Joanna; Selbig, Joachim; Stitt, Mark
A platform has been developed to measure the activity of 23 enzymes that are involved in central carbon and nitrogen metabolism in Arabidopsis thaliana. Activities are assayed in optimized stopped assays and the product then determined using a suite of enzyme cycling assays. The platform requires inexpensive equipment, is organized in a modular manner to optimize logistics, calculates results automatically, combines high sensitivity with throughput, can be robotized, and has a throughput of three to four activities in 100 samples per person/day. Several of the assays, including those for sucrose phosphate synthase, ADP glucose pyrophosphorylase (AGPase), ferredoxin-dependent glutamate synthase, glycerokinase, and shikimate dehydrogenase, provide large advantages over previous approaches. This platform was used to analyze the diurnal changes of enzyme activities in wild-type Columbia-0 (Col-0) and the starchless plastid phosphoglucomutase (pgm) mutant, and in Col-0 during a prolongation of the night. The changes of enzyme activities were compared with the changes of transcript levels determined with the Affymetrix ATH1 array. Changes of transcript levels typically led to strongly damped changes of enzyme activity. There was no relation between the amplitudes of the diurnal changes of transcript and enzyme activity. The largest diurnal changes in activity were found for AGPase and nitrate reductase. Examination of the data and comparison with the literature indicated that these are mainly because of posttranslational regulation. The changes of enzyme activity are also strongly delayed, with the delay varying from enzyme to enzyme. It is proposed that enzyme activities provide a quasi-stable integration of regulation at several levels and provide useful data for the characterization and diagnosis of different physiological states. As an illustration, a decision tree constructed using data from Col-0 during diurnal changes and a prolonged dark treatment was used to
Victoria H. Work
Full Text Available The cyanobacterium Synechococcus sp. PCC 7002 was genetically engineered to synthesize biofuel compatible medium-chain fatty acids during photoautotrophic growth. Expression of a heterologous lauroyl-acyl carrier protein (C12:0-ACP thioesterase with concurrent deletion of the endogenous putative acyl-ACP synthetase led to secretion of transesterifiable C12:0 fatty acid in CO2-supplemented batch cultures. When grown at steady state over a range of light intensities in an LED turbidostat photobioreactor, the C12-secreting mutant exhibited a modest reduction in growth rate and increased O2 evolution relative to the wildtype. Inhibition of i glycogen synthesis by deletion of the glgC-encoded ADP-glucose pyrophosphorylase (AGPase, and ii protein synthesis by nitrogen deprivation were investigated as potential mechanisms for metabolite redistribution to increase fatty acid synthesis. Deletion of AGPase led to a ten-fold decrease in reducing carbohydrates and secretion of organic acids during nitrogen deprivation consistent with an energy spilling phenotype. When the carbohydrate-deficient background (∆glgC was modified for C12 secretion, no increase in C12 was achieved during nutrient replete growth, and no C12 was recovered from any strain upon nitrogen deprivation under the conditions used. At steady state, the growth rate of the ∆glgC strain saturated at a lower light intensity than the wildtype, but O2 evolution was not compromised and became increasingly decoupled from growth rate with rising irradiance. Photophysiological properties of the ∆glgC strain suggest energy dissipation from photosystem II and reconfiguration of electron flow at the level of the plastoquinone pool.
Sugar metabolism, chip color, invertase activity, and gene expression during long-term cold storage of potato (Solanum tuberosum) tubers from wild-type and vacuolar invertase silencing lines of Katahdin.
Wiberley-Bradford, Amy E; Busse, James S; Jiang, Jiming; Bethke, Paul C
Storing potato tubers at low temperatures minimizes sprouting and disease but can cause an accumulation of reducing sugars in a process called cold-induced sweetening. Tubers with increased amounts of reducing sugars produce dark-colored, bitter-tasting fried products with elevated amounts of acrylamide, a possible carcinogen. Vacuolar invertase (VInv), which converts sucrose produced by starch breakdown to glucose and fructose, is the key determinant of reducing sugar accumulation during cold-induced sweetening. In this study, wild-type tubers and tubers in which VInv expression was reduced by RNA interference were used to investigate time- and temperature-dependent changes in sugar contents, chip color, and expression of VInv and other genes involved in starch metabolism in tubers during long-term cold storage. VInv activities and tuber reducing sugar contents were much lower, and tuber sucrose contents were much higher, in transgenic than in wild-type tubers stored at 3-9°C for up to eight months. Large differences in VInv mRNA accumulation were not observed at later times in storage, especially at temperatures below 9°C, so differences in invertase activity were likely established early in the storage period and maintained by stability of the invertase protein. Sugar contents, chip color, and expression of several of the studied genes, including AGPase and GBSS, were affected by storage temperature in both wild-type and transgenic tubers. Though transcript accumulation for other sugar-metabolism genes was affected by storage temperature and duration, it was essentially unaffected by invertase silencing and altered sugar contents. Differences in stem- and bud-end sugar contents in wild-type and transgenic tubers suggested different compartmentalization of sucrose at the two ends of stored tubers. VInv silencing significantly reduced cold-induced sweetening in stored potato tubers, likely by means of differential VInv expression early in storage. Transgenic
Sawicki, Mélodie; Ait Barka, Essaid; Clément, Christophe; Gilard, Françoise; Tcherkez, Guillaume; Baillieul, Fabienne; Vaillant-Gaveau, Nathalie; Jacquard, Cédric
Cold nights impact grapevine flower development and fruit set. Regulation at the female meiosis stepmay be of considerable importance for further understanding on how flower reacts to cold stress. In this study, the impact of chilling temperature (0 °C overnight) on carbon metabolism was investigated in the inflorescencesof two cultivars, Pinot noir (Pinot) and Gewurztraminer (Gewurtz.). Fluctuations in photosynthetic activity and carbohydrate metabolism were monitored by analyzing gas exchanges, simultaneous photosystem I and II activities, andcarbohydrate content. Further, the expression of PEPc, PC, FNR, ISO, OXO, AGPase, amylases and invertase genes, activities of various enzymes, as well as metabolomic analysis were attained. Results showed that the chilling night has different impacts depending on cultivars. Thus, in Gewurtz., net photosynthesis (Pn) was transiently increased whereas, in Pinot, the Pn increase was persistent and concomitant with an inhibition of respiration. However, during the days following the cold night, photosynthetic activity was decreased, and the cyclic electron flow was inhibited in Gewurtz., suggesting lower efficient energy dissipation. Likewise, metabolomic analysis revealed that several metabolites contents (namely alanine, GABA, lysine and succinate)were distinctly modulated in the two cultivars. Taking together, these results reflect a photosynthetic metabolism alteration or internal CO2 conductance in Gewurtz. explaining partly why Pinot is less susceptible to cold stress. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Li, Xiangyang; Xing, Jinpeng; Gianfagna, Thomas J.; Janes, Harry W.
ADP-glucose pyrophosphorylase (AGPase, EC126.96.36.199) is a key regulatory enzyme in starch biosynthesis. The enzyme is a heterotetramer with two S and two B subunits. In tomato, there are three multiple forms of the S subunit gene. Agp S1, S2 and B are highly expressed in fruit from 10 to 25 days after anthesis. Agp S3 is only weakly expressed in fruit. Sucrose significantly elevates expression of Agp S1, S2 and B in both leaves and fruits. Agp S1 exhibits the highest degree of regulation by sucrose. In fact, sucrose may be required for Agp S1 expression. For excised leaves incubated in water, no transcripts for Agp S1 could be detected in the absence of sucrose, whereas it took up to 16 h in water before transcripts were no longer detectable for Agp S2 and B. Neither Agp S3 nor the tubulin gene is affected by sucrose, demonstrating that this response is specifically regulated by a carbohydrate metabolic signal, and is not due to a general increase in metabolism caused by sucrose treatment. Truncated versions of the promoter for Agp S1 indicate that a specific region 1.3-3.0 kb upstream from the transcription site is responsible for sucrose sensitivity. This region of the S1 promoter contains several cis-acting elements present in the promoters of other genes that are also regulated by sucrose. c2002 Elsevier Science Ireland Ltd. All rights reserved.
Full Text Available Mutated genetic resources play an important role in gene/allele characterization. Currently, there are few hexaploid winter wheat mutated resources available. Here, we developed a hexaploid winter wheat resource by inducing mutations via EMS treatment by the single seed descent method. A broad mutation spectrum with high mutation frequency (∼19% on phenotypic variations was identified. These mutations included spike, leaf and seed morphology, plant architecture, and heading date variations. To evaluate the efficiency of the resource for reverse genetic analysis, allelic variations in the TaAGP.L-B1 gene, encoding the AGPase large subunit, were screened by the TILLING approach. Four missense mutations were identified and one allele in line E3-1-3, resulted in an amino acid change predicated to have severe effects on gene function. The other three mutations were predicted to have no effect. Results of gene expression patterns and grain starch content demonstrated that the novel allele in E3-1-3 altered the function of TaAGP.L-B1. Our results indicated that this mutated genetic wheat resource contained broad spectrum phenotypic and genotypic variations, that may be useful for wheat improvement, gene discovery, and functional genomics.
Tang, Yawei; Zeng, Xingquan; Wang, Yulin; Bai, Lijun; Xu, Qijun; Wei, Zexiu; Yuan, Hongjun; Nyima, Tashi
Hulless barley, with its unique nutritional value and potential health benefits, has increasingly attracted attentions in recent years. However, the transcription dynamics during hulless barley grain development is not well understood. In the present study, we investigated the transcriptome changes during barley grain development using Illumina paired-end RNA-sequencing. Two datasets of the developing grain transcriptomes from two barley landraces with the differential seed starch synthesis traits were generated, and comparative transcriptome approach in both genotypes was performed. The results showed that 38 differentially expressed genes (DEGs) were found co-modulated in both genotypes during the barley grain development. Of those, the proteins encoded by most of those DGEs were found, such as alpha-amylase-related proteins, lipid-transfer protein, homeodomain leucine zipper (HD-Zip), NUCLEAR FACTOR-Y, subunit B (NF-YBs), as well as MYB transcription factors. More interestingly, two genes Hvulgare_GLEAN_10012370 and Hvulgare_GLEAN_10021199 encoding SuSy, AGPase (Hvulgare_GLEAN_10033640 and Hvulgare_GLEAN_10056301), as well as SBE2b (Hvulgare_GLEAN_10018352) were found to significantly contribute to the regulatory mechanism during grain development in both genotypes. Moreover, six co-expression modules associated with specific biological processes or pathways (M1 to M6) were identified by consensus co-expression network. Significantly enriched pathways of those module genes showed difference in both genotypes. These results will expand our understanding of the complex molecular mechanism of starch synthesis during barley grain development.
Full Text Available Cassava, being one of the top three tuberous crops, features highly efficient starch accumulation in the storage root to adapt the tropical resources and environments. The molecular mechanism for the process, however, is still unclear. ADP-glucose pyrophosphorylase, the first and rate-limited enzyme in starch biosynthesis pathway, is a heterotetramer comprised of two small/catalytic and two large/modulatory subunits. To understand the regulation of MeAGPase, the promoter of a highly expressed small subunit, MeAGPs1a, was used as bait for a yeast one-hybrid assay to screen storage root cDNA library. One cDNA, coding for a small auxin-up RNA protein, named MeSAUR1, was isolated from cassava. MeSAUR1 could bind to the promoter of MeAGPS1a in yeast one-hybrid test and in vitro, and was located in cell nucleus. MeSAUR1 displayed a higher transcript level in cassava root cortex, and its expression was induced by indole-3-acetic acid, gibberellin and ethylene, but repressed by abscisic acid. A dual-luciferase interaction test further convinced that MeSAUR1 could bind to the promoter of MeAGPS1a, and positively regulate the transcription of MeAGPS1a in cassava.
Fan, Weijuan; Wang, Hongxia; Wu, Yinliang; Yang, Nan; Yang, Jun; Zhang, Peng
Iron (Fe) deficiency is one of the most common micronutrient deficiencies limiting crop production globally, especially in arid regions because of decreased availability of iron in alkaline soils. Sweet potato [Ipomoea batatas (L.) Lam.] grows well in arid regions and is tolerant to Fe deficiency. Here, we report that the transcription of type I H + -pyrophosphatase (H + -PPase) gene IbVP1 in sweet potato plants was strongly induced by Fe deficiency and auxin in hydroponics, improving Fe acquisition via increased rhizosphere acidification and auxin regulation. When overexpressed, transgenic plants show higher pyrophosphate hydrolysis and plasma membrane H + -ATPase activity compared with the wild type, leading to increased rhizosphere acidification. The IbVP1-overexpressing plants showed better growth, including enlarged root systems, under Fe-sufficient or Fe-deficient conditions. Increased ferric precipitation and ferric chelate reductase activity in the roots of transgenic lines indicate improved iron uptake, which is also confirmed by increased Fe content and up-regulation of Fe uptake genes, e.g. FRO2, IRT1 and FIT. Carbohydrate metabolism is significantly affected in the transgenic lines, showing increased sugar and starch content associated with the increased expression of AGPase and SUT1 genes and the decrease in β-amylase gene expression. Improved antioxidant capacities were also detected in the transgenic plants, which showed reduced H 2 O 2 accumulation associated with up-regulated ROS-scavenging activity. Therefore, H + -PPase plays a key role in the response to Fe deficiency by sweet potato and effectively improves the Fe acquisition by overexpressing IbVP1 in crops cultivated in micronutrient-deficient soils. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.
Ranjeet R. Kumar
Full Text Available Wheat is highly prone to terminal heat stress (HS under late-sown conditions. Delayed- sowing is one of the preferred methods to screen the genotypes for thermotolerance under open field conditions. We investigated the effect of terminal HS on the thermotolerance of four popular genotypes of wheat i.e. WR544, HD2967, HD2932, and HD2285 under field condition. We observed significant variations in the biochemical parameters like protein content, antioxidant activity, proline and total reducing sugar content in leaf, stem, and spike under normal (26 ± 2°C and terminal HS (36 ± 2°C conditions. Maximum protein, sugars and proline was observed in HD2967, as compared to other cultivars under terminal HS. Wheat cv. HD2967 showed more adaptability to the terminal HS. Differential protein-profiling in leaves, stem and spike of HD2967 under normal (26 ± 2°C and terminal HS (36 ± 2°C showed expression of some unique protein spots. MALDI-TOF/MS analysis showed the DEPs as RuBisCO (Rub, RuBisCO activase (Rca, oxygen evolving enhancer protein (OEEP, hypothetical proteins, etc. Expression analysis of genes associated with photosynthesis (Rub and Rca and starch biosynthesis pathway (AGPase, SSS and SBE showed significant variations in the expression under terminal HS. HD2967 showed better performance, as compared to other cultivars under terminal HS. SSS activity observed in HD2967 showed more stability under terminal HS, as compared with other cultivars. Triggering of different biochemical parameters in response to terminal HS was observed to modulate the plasticity of carbon assimilatory pathway. The identified DEPs will enrich the proteomic resources of wheat and will provide a potential biochemical marker for screening wheat germplasm for thermotolerance. The model hypothesized will help the researchers to work in a more focused way to develop terminal heat tolerant wheat without compromising with the quality and quantity of grains.
Kumar, Ranjeet R; Goswami, Suneha; Shamim, Mohammed; Mishra, Upama; Jain, Monika; Singh, Khushboo; Singh, Jyoti P; Dubey, Kavita; Singh, Shweta; Rai, Gyanendra K; Singh, Gyanendra P; Pathak, Himanshu; Chinnusamy, Viswanathan; Praveen, Shelly
Wheat is highly prone to terminal heat stress (HS) under late-sown conditions. Delayed- sowing is one of the preferred methods to screen the genotypes for thermotolerance under open field conditions. We investigated the effect of terminal HS on the thermotolerance of four popular genotypes of wheat i.e. WR544, HD2967, HD2932, and HD2285 under field condition. We observed significant variations in the biochemical parameters like protein content, antioxidant activity, proline and total reducing sugar content in leaf, stem, and spike under normal (26 ± 2°C) and terminal HS (36 ± 2°C) conditions. Maximum protein, sugars and proline was observed in HD2967, as compared to other cultivars under terminal HS. Wheat cv. HD2967 showed more adaptability to the terminal HS. Differential protein-profiling in leaves, stem and spike of HD2967 under normal (26 ± 2°C) and terminal HS (36 ± 2°C) showed expression of some unique protein spots. MALDI-TOF/MS analysis showed the DEPs as RuBisCO (Rub), RuBisCO activase (Rca), oxygen evolving enhancer protein (OEEP), hypothetical proteins, etc. Expression analysis of genes associated with photosynthesis (Rub and Rca) and starch biosynthesis pathway (AGPase, SSS and SBE) showed significant variations in the expression under terminal HS. HD2967 showed better performance, as compared to other cultivars under terminal HS. SSS activity observed in HD2967 showed more stability under terminal HS, as compared with other cultivars. Triggering of different biochemical parameters in response to terminal HS was observed to modulate the plasticity of carbon assimilatory pathway. The identified DEPs will enrich the proteomic resources of wheat and will provide a potential biochemical marker for screening wheat germplasm for thermotolerance. The model hypothesized will help the researchers to work in a more focused way to develop terminal heat tolerant wheat without compromising with the quality and quantity of grains.
Guo, Ling; Ding, Yanqiang; Xu, Yaliang; Li, Zhidan; Jin, Yanling; He, Kaize; Fang, Yang; Zhao, Hai
Landoltia punctata has been considered as a potential bioenergy crop due to its high biomass and starch yields in different cultivations. Cobalt and nickel are known to induce starch accumulation in duckweed. We monitored the growth rate, net photosynthesis rate, total chlorophyll content, Rubisco activity, Co2+ and Ni2+ contents, activity of antioxidant enzymes, starch content and activity of related enzymes under various concentrations of cobalt and nickel. The results indicate that Co2+ and Ni2+ (≤0.5mgL-1) can facilitate growth in the beginning. Although the growth rate, net photosynthesis rate, chlorophyll content and Rubisco activity were significantly inhibited at higher concentrations (5mgL-1), the starch content increased sharply up to 53.3% dry weight (DW) in L. punctata. These results were attributed to the increase in adenosine diphosphate-glucose pyrophosphorylase (AGPase) and soluble starch synthase (SSS) activities and the decrease in α-amylase activity upon exposure to excess Co2+ and Ni2+. In addition, a substantial increase in the antioxidant enzyme activities and high flavonoid contents in L. punctata may have largely resulted in the metal tolerance. Furthermore, the high Co2+ and Ni2+ contents (2012.9±18.8 and 1997.7±29.2mgkg-1 DW) in the tissue indicate that L. punctata is a hyperaccumulator. Thus, L. punctata can be considered as a potential candidate for the simultaneous bioremediation of Co2+- and Ni2+-polluted water and high-quality biomass production. Copyright © 2017 Elsevier B.V. All rights reserved.
Chang, Tao-Shan; Liu, Chih-Wei; Lin, Yu-Ling; Li, Chao-Yi; Wang, Arthur Z; Chien, Min-Wei; Wang, Chang-Sheng; Lai, Chien-Chen
Our results not only provide a comprehensive overview of the starch biosynthetic pathway in the developing endosperm but also reveal some important protein markers that regulate the synthesis of starch. In human diets, rice (Oryza sativa L.) is an important source of starch, a substantial amount of which is accumulated in developing endosperm. A better understanding of the complicated pathways involved in starch biosynthesis is needed to improve the yield and quality of rice and other cereal crops through breeding. One pure line rice mutant, SA0419, was induced from a wild-type rice, TNG67, by sodium azide mutagenesis; therefore, TNG67 and SA0419 share the same genetic background. SA0419 is, however, a unique glutinous rice with a lower amylose content (8%) than that of TNG67 (20%), and the grains of SA0419 develop earlier and faster than those of TNG67. In this study, we used a comparative proteomic analysis to identify the differentially expressed proteins that may explain the differences in starch biosynthesis and the characteristics of TNG67 and SA0419. A gel-based proteomic approach was applied to profile the expressed proteome in the developing endosperm of these two rice varieties by nano-LC/MS/MS. Several over-expressed proteins were found in SA0419, such as plastidial ADP-glucose pyrophosphorylase (AGPase), phosphoglucomutase (PGM), pyrophosphate-fructose 6-phosphate 1-phosphotransferase (PFP), 6-phosphofructokinase (PFK), pyruvate phosphate dikinase (PPDK), starch branching enzymes (SBE) and starch debranching enzyme (SDBE), with those proteins mainly being involved in the pathways of starch metabolism and PPDK-mediated gluconeogenesis. Those over-expressed enzymes may contribute to the relatively early development, similar starch accumulation and rapid grain filling of SA0419 as compared with TNG67. This study provides a detailed biochemical description of starch biosynthesis and related information regarding a unique starch mutant that may assist future
Zale, Janice; Jung, Je Hyeong; Kim, Jae Yoon; Pathak, Bhuvan; Karan, Ratna; Liu, Hui; Chen, Xiuhua; Wu, Hao; Candreva, Jason; Zhai, Zhiyang; Shanklin, John; Altpeter, Fredy
Elevating the lipid content in vegetative tissues has emerged as a new strategy for increasing energy density and biofuel yield of crops. Storage lipids in contrast to structural and signaling lipids are mainly composed of glycerol esters of fatty acids, also known as triacylglycerol (TAG). TAGs are one of the most energy-rich and abundant forms of reduced carbon available in nature. Therefore, altering the carbon-partitioning balance in favour of TAG in vegetative tissues of sugarcane, one of the highest yielding biomass crops, is expected to drastically increase energy yields. Here we report metabolic engineering to elevate TAG accumulation in vegetative tissues of sugarcane. Constitutive co-expression of WRINKLED1 (WRI1), diacylglycerol acyltransferase1-2 (DGAT1-2) and oleosin1 (OLE1) and simultaneous cosuppression of ADP-glucose pyrophosphorylase (AGPase) and a subunit of the peroxisomal ABC transporter1 (PXA1) in transgenic sugarcane elevated TAG accumulation in leaves or stems by 95- or 43-fold to 1.9% or 0.9% of dry weight (DW), respectively, while expression or suppression of one to three of the target genes increased TAG levels by 1.5- to 9.5-fold. Accumulation of TAG in vegetative progeny plants was consistent with the results from primary transgenics and contributed to a total fatty acid content of up to 4.7% or 1.7% of DW in mature leaves or stems, respectively. Lipid droplets were visible within mesophyll cells of transgenic leaves by confocal fluorescence microscopy. These results provide the basis for optimizations of TAG accumulation in sugarcane and other high yielding biomass grasses and will open new prospects for biofuel applications. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.
Li, XueYan; Wang, ChunXia; Cheng, JinYun; Zhang, Jing; da Silva, Jaime A Teixeira; Liu, XiaoYu; Duan, Xin; Li, TianLai; Sun, HongMei
The formation and development of bulblets are crucial to the Lilium genus since these processes are closely related to carbohydrate metabolism, especially to starch and sucrose metabolism. However, little is known about the transcriptional regulation of both processes. To gain insight into carbohydrate-related genes involved in bulblet formation and development, we conducted comparative transcriptome profiling of Lilium davidii var. unicolor bulblets at 0 d, 15 d (bulblets emerged) and 35 d (bulblets formed a basic shape with three or four scales) after scale propagation. Analysis of the transcriptome revealed that a total of 52,901 unigenes with an average sequence size of 630 bp were generated. Based on Clusters of Orthologous Groups (COG) analysis, 8% of the sequences were attributed to carbohydrate transport and metabolism. The results of KEGG pathway enrichment analysis showed that starch and sucrose metabolism constituted the predominant pathway among the three library pairs. The starch content in mother scales and bulblets decreased and increased, respectively, with almost the same trend as sucrose content. Gene expression analysis of the key enzymes in starch and sucrose metabolism suggested that sucrose synthase (SuSy) and invertase (INV), mainly hydrolyzing sucrose, presented higher gene expression in mother scales and bulblets at stages of bulblet appearance and enlargement, while sucrose phosphate synthase (SPS) showed higher expression in bulblets at morphogenesis. The enzymes involved in the starch synthetic direction such as ADPG pyrophosphorylase (AGPase), soluble starch synthase (SSS), starch branching enzyme (SBE) and granule-bound starch synthase (GBSS) showed a decreasing trend in mother scales and higher gene expression in bulblets at bulblet appearance and enlargement stages while the enzyme in the cleavage direction, starch de-branching enzyme (SDBE), showed higher gene expression in mother scales than in bulblets. An extensive transcriptome
Yu, Changjiang; Zhao, Xiaowen; Qi, Guang; Bai, Zetao; Wang, Yu; Wang, Shumin; Ma, Yubin; Liu, Qian; Hu, Ruibo; Zhou, Gongke
Duckweed is considered a promising source of energy due to its high starch content and rapid growth rate. Starch accumulation in duckweed involves complex processes that depend on the balanced expression of genes controlled by various environmental and endogenous factors. Previous studies showed that nitrogen starvation induces a global stress response and results in the accumulation of starch in duckweed. However, relatively little is known about the mechanisms underlying the regulation of starch accumulation under conditions of nitrogen starvation. In this study, we used next-generation sequencing technology to examine the transcriptome responses of Lemna aequinoctialis 6000 at three stages (0, 3, and 7 days) during nitrogen starvation in the presence of exogenously applied sucrose. Overall, 2522, 628, and 1832 differentially expressed unigenes (DEGs) were discovered for the treated and control samples. Clustering and enrichment analysis of DEGs revealed several biological processes occurring under nitrogen starvation. Genes involved in nitrogen metabolism showed the earliest responses to nitrogen starvation, whereas genes involved in carbohydrate biosynthesis were responded subsequently. The expression of genes encoding nitrate reductase, glutamine synthetase, and glutamate synthase was down-regulated under nitrogen starvation. The expression of unigenes encoding enzymes involved in gluconeogenesis was up-regulated, while the majority of unigenes involved in glycolysis were down-regulated. The metabolite results showed that more ADP-Glc was accumulated and lower levels of UDP-Glc were accumulated under nitrogen starvation, the activity of AGPase was significantly increased while the activity of UGPase was dramatically decreased. These changes in metabolite levels under nitrogen starvation are roughly consistent with the gene expression changes in the transcriptome. Based on these results, it can be concluded that the increase of ADP-glucose and starch contents
Silva, Angélica; Noronha, Henrique; Dai, Zhanwu; Delrot, Serge; Gerós, Hernâni
Severe leaf removal decreases storage starch and sucrose in grapevine cv. Cabernet Sauvignon fruiting cuttings and modulates the activity of key enzymes and the expression of sugar transporter genes. Leaf removal is an agricultural practice that has been shown to modify vineyard efficiency and grape and wine composition. In this study, we took advantage of the ability to precisely control the number of leaves to fruits in Cabernet Sauvignon fruiting cuttings to study the effect of source-sink ratios (2 (2L), 6 (6L) and 12 (12) leaves per cluster) on starch metabolism and accumulation. Starch concentration was significantly higher in canes from 6L (42.13 ± 1.44 mg g DW-1) and 12L (43.50 ± 2.85 mg g DW-1) than in 2L (22.72 ± 3.10 mg g DW-1) plants. Moreover, carbon limitation promoted a transcriptional adjustment of genes involved in starch metabolism in grapevine woody tissues, including a decrease in the expression of the plastidic glucose-6-phosphate translocator, VvGPT1. Contrarily, the transcript levels of the gene coding the catalytic subunit VvAGPB1 of the VvAGPase complex were higher in canes from 2L plants than in 6L and 12L, which positively correlated with the biochemical activity of this enzyme. Sucrose concentration increased in canes from 2L to 6L and 12L plants, and the amount of total phenolics followed the same trend. Expression studies showed that VvSusy transcripts decreased in canes from 2L to 6L and 12L plants, which correlated with the biochemical activity of insoluble invertase, while the expression of the sugar transporters VvSUC11 and VvSUC12, together with VvSPS1, which codes an enzyme involved in sucrose synthesis, increased. Thus, sucrose seems to control starch accumulation through the adjustment of the cane sink strength.
Simón Pedro Cortés Sierra
months old, in 5 cassava varieties. Important gene expression differences were detected both at the variety and time level. CM523-7 and SM1219-2 showed one of the highest expression levels for AGPase and GBSS genes, while α-amylase showed the lowest level in these two varieties. TMS60444 variety showed similar expression levels in starch biosynthesis-related genes, but conversely also showed the highest α-amylase expression. This correlates with the relative low dry-matter content in TMS60444. Gene expression data reported here will allow complementing actual information on enzymatic activity, in order to identify the most relevant factors in differential starch accumulation between cassava varieties.