Starch Synthesis Research Articles

Regulatory loops between rice transcription factors OsNAC25 and OsNAC20/26 balance starch synthesis.

Several starch synthesis regulators have been identified, but these regulators are situated in the terminus of the regulatory network. Their upstream regulators and the complex regulatory network formed between these regulators remain largely unknown. A previous study demonstrated that NAM, ATAF, and CUC (NAC) transcription factors, OsNAC20 and OsNAC26 (OsNAC20/26), redundantly and positively regulate the accumulation of storage material in rice (Oryza sativa) endosperm. In this study, we detected OsNAC25 as an upstream regulator and interacting protein of OsNAC20/26. Both OsNAC25 mutation and OE resulted in a chalky seed phenotype, decreased starch content, and reduced expression of starch synthesis-related genes, but the mechanisms were different. In the osnac25 mutant, decreased expression of OsNAC20/26 resulted in reduced starch synthesis; however, in OsNAC25-overexpressing plants, the OsNAC25-OsNAC20/26 complex inhibited OsNAC20/26 binding to the promoter of starch synthesis-related genes. In addition, OsNAC20/26 positively regulated OsNAC25. Therefore, the mutual regulation between OsNAC25 and OsNAC20/26 forms a positive regulatory loop to stimulate the expression of starch synthesis-related genes and meet the great demand for starch accumulation in the grain filling stage. Simultaneously, a negative regulatory loop forms among the 3 proteins to avoid the excessive expression of starch synthesis-related genes. Collectively, our findings demonstrate that both promotion and inhibition mechanisms between OsNAC25 and OsNAC20/26 are essential for maintaining stable expression of starch synthesis-related genes and normal starch accumulation.

Anthocyanins act as a sugar-buffer and an alternative electron sink in response to starch depletion during leaf senescence: a case study on a typical anthocyanic tree species, Acer japonicum.

We hypothesized that anthocyanins act as a sugar-buffer and an alternative electron sink during leaf senescence to prevent sugar-mediated early senescence and photoinhibition. To elucidate the anthocyanin role, we monitored seasonal changes in photosynthetic traits, sugar, starch and N contents, pigment composition, and gene expression profiles in leaves exposed to substantially different light conditions within a canopy of an adult tree of fullmoon maple (Acer japonicum). Enhancement of starch amylolysis accompanied with cessation of starch synthesis occurred in the same manner independent of light conditions. Leaf sugar contents increased, but reached upper limits in the late stage of leaf senescence, even though leaf anthocyanins further increased after complete depletion of starch. Sun-exposed leaves maintained higher energy consumption via electron flow than shade-grown leaves during leaf N resorption. Thus, anthocyanins accumulated in sun-exposed leaves might have a regulative role as a sugar buffer, retarding leaf senescence, and an indirect photoprotective role as an alternative sink for electron consumption to compensate declines in other metabolic processes such as starch and protein synthesis. In this context, anthocyanins might be key substrates protecting both outer-canopy leaves (against photoinhibition) and inner-canopy leaves (via shading by outer-canopy leaves) from high light stress during N resorption.

Grain Chalkiness Is Decreased by Balancing the Synthesis of Protein and Starch in Hybrid Indica Rice Grains under Nitrogen Fertilization.

The important reason for the commercial value of hybrid rice suffering is due to excessive chalkiness, and the biosynthesis of starch and proteins is critical for regulating chalkiness; however, it is currently unclear how the application of N fertilizer affects grains to reduce their chalkiness and improve their quality. The 2019, 2020, and 2021 trials were conducted in a split-plot design, with high and low chalky varieties as the main plot and N fertilizer rate as the split-plot. The effects of fertilization with 75, 150, and 225 kg N ha-1 on the dynamic synthesis of starch, protein, and endogenous hormones and on the amino acid of hybrid indica rice kernels with different degrees of chalkiness were investigated. Grain physiological activity was higher in low-chalky varieties than in high-chalky varieties, and these physiological parameters were strongly associated with chalkiness formation. Higher N fertilization (150 and 225 kg N ha-1) significantly reduced the proportion of chalky grains (8.93-28.02%) and chalkiness (8.61-33.99%) compared with 75 kg N ha-1. Increased N fertilization decreased the activities of granule-bound starch synthase and starch-debranching enzyme, but significantly increased adenosine diphosphate glucose pyrophosphorylase, soluble starch synthase, and starch-branching enzyme activities, synergistically improving glutamate synthetase and glutamine synthetase enzyme activities, which tended to support the synthesis of amylopectin, α-ketoglutarate, and 3-phosphoglyceric acid-derived amino acids in the endosperm cells of the grains; this favored starch and protein accumulation in the grains at 6-30 days after anthesis. Additionally, N application promoted the synthesis of endogenous hormones 1-aminocyclopropane-1-carboxylic acid, gibberellins, and abscisic acid in grains. Hence, N fertilization reduced the rice chalkiness in hybrid indica rice varieties by balancing grain protein and starch composition and enhancing some endogenous hormone synthesis.

Transcriptome Analysis Reveals Novel Genes Potentially Involved in Tuberization in Potato

The formation and development of tubers, the primary edible and economic organ of potatoes, directly affect their yield and quality. The regulatory network and mechanism of tuberization have been preliminarily revealed in recent years, but plenty of relevant genes remain to be discovered. A few candidate genes were provided due to the simplicity of sampling and result analysis of previous transcriptomes related to tuberization. We sequenced and thoroughly analyzed the transcriptomes of thirteen tissues from potato plants at the tuber proliferation phase to provide more reference information and gene resources. Among them, eight tissues were stolons and tubers at different developmental stages, which we focused on. Five critical periods of tuberization were selected to perform an analysis of differentially expressed genes (DEGs), according to the results of the tissue correlation. Compared with the unswollen stolons (Sto), 2751, 4897, 6635, and 9700 DEGs were detected in the slightly swollen stolons (Sto1), swollen stolons (Sto2), tubers of proliferation stage 1 (Tu1), and tubers of proliferation stage 4 (Tu4). A total of 854 transcription factors and 164 hormone pathway genes were identified in the DEGs. Furthermore, three co-expression networks associated with Sto–Sto1, Sto2–Tu1, and tubers of proliferation stages two to five (Tu2–Tu5) were built using the weighted gene co-expression network analysis (WGCNA). Thirty hub genes (HGs) and 30 hub transcription factors (HTFs) were screened and focalized in these networks. We found that five HGs were reported to regulate tuberization, and most of the remaining HGs and HTFs co-expressed with them. The orthologs of these HGs and HTFs were reported to regulate processes (e.g., flowering, cell division, hormone synthesis, metabolism and signal transduction, sucrose transport, and starch synthesis) that were also required for tuberization. Such results further support their potential to control tuberization. Our study provides insights and countless candidate genes of the regulatory network of tuberization, laying the foundation for further elucidating the genetic basis of tuber development.

The cytosolic isoform of triosephosphate isomerase, ZmTPI4, is required for kernel development and starch synthesis in maize (Zea mays L.)

Triosephosphate isomerase (TPI) is an enzyme that functions in plant energy production, accumulation, and conversion. To understand its function in maize, we characterized a maize TPI mutant, zmtpi4. In comparison to the wild type, zmtpi4 mutants showed altered ear development, reduced kernel weight and starch content, modified starch granule morphology, and altered amylose and amylopectin content. Protein, ATP, and pyruvate contents were reduced, indicating ZmTPI4 was involved in glycolysis. Although subcellular localization confirmed ZmTPI4 as a cytosolic rather than a plastid isoform of TPI, the zmtpi4 mutant showed reduced leaf size and chlorophyll content. Overexpression of ZmTPI4 in Arabidopsis led to enlarged leaves and increased seed weight, suggesting a positive regulatory role of ZmTPI4 in kernel weight and starch content. We conclude that ZmTPI4 functions in maize kernel development, starch synthesis, glycolysis, and photosynthesis.

The role of LED supplementary lighting in promoting graft necrotic layer formation in pumpkin-cucumber grafts

The rapid formation of the graft necrotic layer is crucial for preventing organic substance leakage and warding off external infections, significantly enhancing both the speed and quality of graft healing. This study investigates the impact of LED supplementary lighting on pumpkin-cucumber grafts, unveiling the molecular processes underlying necrotic layer formation. Specifically, three replications were conducted, where post-grafting cucumber seedlings were placed separately in healing chambers with LED light intensities of 0 μmol/(m2·s) and 50 ± 1 μmol/(m2·s) for three days. Anatomical observations, enzyme activity assays, energy product content detection, and a more comprehensive transcriptome sequencing analysis on the graft union of the rootstock and scion were conducted. Anatomical observations revealed that LED supplementary lighting accelerates the formation of the pumpkin-cucumber graft necrotic layer, establishing a complete layer by the second day post-grafting, one day earlier than the control. Additionally, at day 3 post-grafting, the activities of POD and PPO enzymes at the rootstock-scion junction significantly surpassed the control, exhibiting a remarkable increase of 74.12 % and 48.96 %, respectively (p < 0.01). Moreover, soluble sugar and ATP levels were notably higher at day 3 post-grafting in comparison to the control, showing significant differences (p < 0.05). Transcriptomic analysis unveiled that LED supplementary lighting not only enhances scion sugar metabolism but also stimulates the upregulation of sugar synthesis genes (SPP1, RPV1) and starch synthesis genes (AGPS1, WAXY, SBEⅡ), while downregulating the starch degradation gene LECRK71 when compared to the control. This orchestrated modulation leads to the accumulation of sugars and starch, providing substantial energy and material foundation for necrotic layer formation. Furthermore, LED supplementation also influences the hormone signaling transduction pathway in the scion, notably upregulating the gene Os01g0656200 involved in abscisic acid signaling when compared to the control, thereby furthering the formation of the necrotic layer. Overall, our research showed that LED supplementary lighting accelerates the formation of the necrotic layer in pumpkin-cucumber grafts by enhancing enzyme activities, sugar metabolism, genetic pathways related to starch accumulation, and influencing hormone signal transduction pathways, notably upregulating genes involved in abscisic acid signaling, providing a robust molecular foundation for early necrotic layer development compared to control conditions. These research findings not only provide a valuable reference for understanding graft healing mechanisms but also demonstrate the promising prospects of LED modern seedling technology. Additionally, the research, which is limited to specific pumpkin and cucumber varieties in graft experiments, necessitates further exploration to validate its broader applicability across diverse plant varieties and grafting methods.

Evolutionary and synteny analysis of HIS1, BADH2, GBSS1, and GBSS2 in rice: insights for effective introgression breeding strategies

The key genes BADH2, GBSS1, GBSS2, and HIS1 regulate the fragrance, starch synthesis, and herbicide resistance in rice. Although the molecular functions of four genes have been investigated in the Oryza sativa species, little is known regarding their evolutionary history in the Oryza genus. Here, we studied the evolution of four focal genes in 10 Oryza species using phylogenetic and syntenic approaches. The HIS1 family underwent several times of tandem duplication events in the Oryza species, resulting in copy number variation ranging from 2 to 7. At most one copy of BADH2, GBSS1, and GBSS2 orthologs were identified in each Oryza species, and gene loss events of BADH2 and GBSS2 were identified in three Oryza species. Gene transfer analysis proposed that the functional roles of GBSS1 and GBSS2 were developed in the Asian and African regions, respectively, and most allelic variations of BADH2 in japonica rice emerged after the divergence between the Asian and African rice groups. These results provide clues to determine the origin and evolution of the key genes in rice breeding as well as valuable information for molecular breeders and scientists to develop efficient strategies to simultaneously improve grain quality and yield potential in rice.

Transcriptional dynamics in source-sink tissues identifies molecular factors regulating the corm development process in saffron (Crocus sativus L.).

Geophytic plants have evolved to develop underground storage organs (USO) in the active growing season to withstand harsh environments as well as to coordinate growth and reproduction when conditions are favourable. Saffron is an autumn flowering geophyte and an expensive spice crop restricted to certain geographical locations in the world. Saffron, being sterile, does not produce seeds and thus propagates only through corms, the quality of which determines its yield. Corm development in saffron is unexplored and the underlying molecular mechanism is still elusive. In this study, we performed an extensive characterisation of the transcriptional dynamics in the source (leaf) and sink (corm) tissues during corm development in saffron. Via morphological and transcriptome studies, we identified molecular factors regulating corm development process in saffron, which defined corm development into three stages: the initiation stage demonstrates enhanced vegetative growth aboveground and swelling of shoot base belowground due to active cell division & carbohydrate storage; the bulking stage comprises of increased source and sink strength, active photosynthesis, circadian gating and starch accumulation; the maturation stage represents reduced source and sink strength, lowered photosynthesis, sugar transport, starch synthesis and cell cycle arrest. The global view of transcriptional changes in source and sink identifies similar and new molecular factors involved in the saffron corm development process compared to USO formation in other geophytes and provides a valuable resource for dissecting the molecular network underlying the corm development. We propose a hypothetical model based on data analysis, of how molecular factors via environmental cues can regulate the corm development process in saffron.

Starch Plays a Key Role in Sporosorus Formation by the Powdery Scab Pathogen Spongospora subterranea.

Powdery scab disease, caused by the soilborne protist Spongospora subterranea f. sp. subterranea, poses a major constraint to potato production worldwide. Disease symptoms include damage to the tuber skin and the formation of root galls. This study aimed to investigate the potential mechanism behind the formation of sporosori, which are aggregates of resting spores, within root galls. Scanning electron microscopy analysis revealed that the early stage of gall formation, characterized by a white color, involved the accumulation of starch grains, which later disappeared as the gall matured and turned brown. The mature brown galls were found to contain fully formed sporosori. Light microscopy examination of ultramicrotome sections of the root galls showed that the high-amylopectin starches were surrounded by a plasmodium, a precursor to sporosorus. These findings suggest that starch grains contribute to the formation of a sponge-like structure within the sporosori. A significant reduction in total starch levels in both the root galls and their associated roots was observed compared with healthy roots. These findings indicate starch consumption by sporosori during the maturation of root galls. Interestingly, analysis of the transcript levels of starch-related genes showed downregulation of genes encoding starch degrading enzymes and an amylopectin-debranching enzyme, whereas genes encoding a starch synthase and a protein facilitating starch synthesis were upregulated in the infected roots. Overall, our results demonstrate that starch is consumed during sporosorus formation, and the pathogen likely manipulates starch homeostasis to its advantage for sporosorus development within the root galls.

Unveiling the mechanism of source-sink rebalancing in cucumber-pumpkin heterografts: the buffering roles of rootstock cotyledon.

Grafting onto pumpkin rootstock is widely applied in cucumber production to improve growth and yield, as well as to overcome soil-borne diseases and enhance resistance to abiotic stresses. In this study, we constructed the cucumber-pumpkin heterografts with the one-cotyledon grafting method, and examined the effects of heterografting on biomass allocation and sugar partitioning, with cucumber and pumpkin self-grafts used as control. Compared with cucumber self-grafts, heterografting onto pumpkin rootstock promoted photosynthesis in cucumber scion, and led to higher sucrose contents in the 1st true leaf (source) and newly emerged leaf (sink). Thereby, the scion part of heterografts accumulated more biomass than cucumber self-grafts. In contrast, when compared to pumpkin self-grafts, grafting with cucumber scion reduced root vigor and biomass but promoted cotyledon growth in pumpkin rootstock. The roots (sink) of heterografts contained less sucrose and hexoses, and showed reduced sucrose synthase (SuSy) and hexokinase (HXK) activities. However, the rootstock cotyledon (source) contained more sucrose and starch, and showed higher activities of HXK, cell-wall invertase (CWIN), and enzymes for starch synthesis and degradation. Furthermore, removal or shade of rootstock cotyledon led to reduced growth of root and scion. Silencing of CmoMEX1a gene in rootstock cotyledon inhibited maltose export and reduced root growth of heterografts. These results indicated that rootstock cotyledon, especially its starch content, played a buffering role in the growth regulation of cucumber-pumpkin heterografts. Taken together, our results provided a major contribution to our understanding of source-sink sugar partitioning and scion-rootstock growth balancing in cucumber-pumpkin heterografts.

Genome-wide association and co-expression uncovered ZmMYB71 controls kernel starch content in maize

Starch plays a crucial role as a storage component, greatly affecting the grain yield and quality of maize (Zea mays L.). To meet future demands, it is essential to understand the genetic basis of the natural variation in kernel starch content (SC) for maize breeding. Through a genome-wide association study (GWAS), we identified 84 and 96 loci associated with kernel SC within two years that overlapped with 185 candidate genes. The candidate gene ZmMYB71, which encodes a myeloblastosis (MYB)-related transcription factor, exhibited the highest co-expression frequency with starch synthesis genes. We demonstrated that ZmMYB71 functions as a nuclear located transcription repressor, and the kernel SC of mutants increased by over 2.32%, with a minor effect on amylose content or 100-grain weight. Sh1, Sh2, and GBSSI showed up-regulation in mutants by 1.56-, 1.45- and 1.32-fold, respectively, consistently with the RNA sequencing result; their promoter activities may be directly repressed by ZmMYB71 through the GATATC and TTAGGG motifs. Furthermore, the ZmMYB71 elite haplotype Hap1 was present in over 55% of the high-starch maize sub-populations BSSS and PB but only in 7.14% of the low-starch sub-population PA. Comparing the Hap1 haplotype frequencies in different breeding stages found that its frequency in the inbred group released after 2010 is significantly higher at 40.28%, in contrast to 28.57% and 27.94% in the years 1980 and 1990, and 2000, respectively. The finding provides valuable information on the natural variation in SC of the maize kernel and suggests that ZmMYB71 serves as a negative regulator with the potential to be used to improve SC in the kernels.

Orchestrating seed storage protein and starch accumulation toward overcoming yield-quality trade-off in cereal crops.

Achieving high yield and good quality in crops is essential for human food security and health. However, there is usually disharmony between yield and quality. Seed storage protein (SSP) and starch, the predominant components in cereal grains, determine yield and quality, and their coupled synthesis causes a yield-quality trade-off. Therefore, dissection of the underlying regulatory mechanism facilitates simultaneous improvement of yield and quality. Here, we summarize current findings about the synergistic molecular machinery underpinning SSP and starch synthesis in the leading staple cereal crops, including maize, rice and wheat. We further evaluate the functional conservation and differentiation of key regulators and specify feasible research approaches to identify additional regulators and expand insights. We also present major strategies to leverage resultant information for simultaneous improvement of yield and quality by molecular breeding. Finally, future perspectives on major challenges are proposed.

AGPS and BAM genes dramatically improve ‘Ganlv 1′ (Actinidia eriantha) fruit quality through starch metabolism during fruit development

In previous field investigations, we found that Actinidia eriantha has sweeter flavor than other kiwifruit, which provided an opportunity to explore the formation mechanism of sweet flavor. In this study, we selected three cultivars of kiwifruit with different accumulation characters of starch and sugar, i.e., ‘Ganlv 1′ (A. eriantha), ‘Jinkui’ (A. chinensis var. deliciosa), and ‘Jinyan’ (A. eriantha × A. chinensis var. chinensis), as materials to identify the key regulatory enzymes and genes. Our results showed that the maximum starch content in A. eriantha was the highest. Importantly, the A. eriantha also had the highest degradation rate, because of the highest amylase activity in A. eriantha among the cultivars tested. Fifty-nine differentially expressed genes involved in starch metabolism were identified by the transcriptome data, the accuracy of transcriptome data was verified by qRT-PCR analysis. Among these genes, starch synthesis related genes were significantly up-regulated at 120 DAFB in A. eriantha, including AGPS1.1, AGPS1.2 and WAXY1. And key degradation related genes were also identified, such as BAM3.2, BAM3.3, PHO1, PHO2.2, SUS2.1 and SUS2.2. Moreover, transient transformations provided overexpressing AcBAM3.3 in kiwifruit could up-regulate the expression of AcBAM3.3 gene and degrade starch content by 15.1∼22.3 %. In conclusion, the stronger biosynthesis capacity and the faster inversion rate of starch in the fruit of A. eriantha were the reasons for its higher sweet flavor in which benefit to fruit quality.

Modulation of starch synthesis in Arabidopsis via phytochrome B-mediated light signal transduction.

Starch is a major storage carbohydrate in plants and is critical in crop yield and quality. Starch synthesis is intricately regulated by internal metabolic processes and external environmental cues; however, the precise molecular mechanisms governing this process remain largely unknown. In this study, we revealed that high red to far-red (high R:FR) light significantly induces the synthesis of leaf starch and the expression of synthesis-related genes, whereas low R:FR light suppress these processes. Arabidopsis phytochrome B (phyB), the primary R and FR photoreceptor, was identified as a critical positive regulator in this process. Downstream of phyB, basic leucine zipper transcription factor ELONGATED HYPOCOTYL5 (HY5) was found to enhance starch synthesis, whereas the basic helix-loop-helix transcription factors PHYTOCHROME INTERACTING FACTORs (PIF3, PIF4, and PIF5) inhibit starch synthesis in Arabidopsis leaves. Notably, HY5 and PIFs directly compete for binding to a shared G-box cis-element in the promoter region of genes encoding starch synthases GBSS, SS3, and SS4, which leads to antagonistic regulation of their expression and, consequently, starch synthesis. Our findings highlight the vital role of phyB in enhancing starch synthesis by stabilizing HY5 and facilitating PIFs degradation under high R:FR light conditions. Conversely, under low R:FR light, PIFs predominantly inhibit starch synthesis. This study provides insight into the physiological and molecular functions of phyB and its downstream transcription factors HY5 and PIFs in starch synthesis regulation, shedding light on the regulatory mechanism by which plants synchronize dynamic light signals with metabolic cues to module starch synthesis.

Comparative transcriptomic analysis reveals the molecular mechanism underlying seedling heterosis and its relationship with hybrid contemporary seeds DNA methylation in soybean.

Heterosis is widely used in crop production, but phenotypic dominance and its underlying causes in soybeans, a significant grain and oil crop, remain a crucial yet unexplored issue. Here, the phenotypes and transcriptome profiles of three inbred lines and their resulting F1 seedlings were analyzed. The results suggest that F1 seedlings with superior heterosis in leaf size and biomass exhibited a more extensive recompilation in their transcriptional network and activated a greater number of genes compared to the parental lines. Furthermore, the transcriptional reprogramming observed in the four hybrid combinations was primarily non-additive, with dominant effects being more prevalent. Enrichment analysis of sets of differentially expressed genes, coupled with a weighted gene co-expression network analysis, has shown that the emergence of heterosis in seedlings can be attributed to genes related to circadian rhythms, photosynthesis, and starch synthesis. In addition, we combined DNA methylation data from previous immature seeds and observed similar recompilation patterns between DNA methylation and gene expression. We also found significant correlations between methylation levels of gene region and gene expression levels, as well as the discovery of 12 hub genes that shared or conflicted with their remodeling patterns. This suggests that DNA methylation in contemporary hybrid seeds have an impact on both the F1 seedling phenotype and gene expression to some extent. In conclusion, our study provides valuable insights into the molecular mechanisms of heterosis in soybean seedlings and its practical implications for selecting superior soybean varieties.

Heat Stress Responsive Aux/IAA Protein, OsIAA29 Regulates Grain Filling Through OsARF17 Mediated Auxin Signaling Pathway

High temperature during grain filling considerably reduces yield and quality in rice, but its molecular mechanisms are not fully understood. We investigated the functions of a seed preferentially expressed Aux/IAA gene, OsIAA29, under high temperature-stress in grain filling using CRISPR/Cas9, RNAi, and overexpression. We observed that the osiaa29 had a higher percentage of shrunken and chalkiness seed, as well as lower 1000-grain weight than ZH11 under high temperature. Meanwhile, the expression of OsIAA29 was induced and the IAA content was remarkably reduced in the ZH11 seeds under high temperature. In addition, OsIAA29 may enhance the transcriptional activation activity of OsARF17 through competition with OsIAA21 binding to OsARF17. Finally, chromatin immunoprecipitation quantitative real-time PCR (ChIP-qPCR) results proved that OsARF17 regulated expression of several starch and protein synthesis related genes (like OsPDIL1-1, OsSS1, OsNAC20, OsSBE1, and OsC2H2). Therefore, OsIAA29 regulates seed development in high temperature through competition with OsIAA21 in the binding to OsARF17, mediating auxin signaling pathway in rice. This study provides a theoretical basis and gene resources for auxin signaling and effective molecular design breeding.

Radiation-assisted synthesis of water soluble starch encapsulated copper nanoparticles and its applicability toward photocatalytic reduction of p-nitrophenol

Radiation-assisted synthesis of water soluble starch encapsulated copper nanoparticles and its applicability toward photocatalytic reduction of p-nitrophenol

Transcriptomic and physiological analysis of the response of Spirodela polyrrhiza to sodium nitroprusside

BackgroundSpirodela polyrrhiza is a simple floating aquatic plant with great potential in synthetic biology. Sodium nitroprusside (SNP) stimulates plant development and increases the biomass and flavonoid content in some plants. However, the molecular mechanism of SNP action is still unclear.ResultsTo determine the effect of SNP on growth and metabolic flux in S. polyrrhiza, the plants were treated with different concentrations of SNP. Our results showed an inhibition of growth, an increase in starch, soluble protein, and flavonoid contents, and enhanced antioxidant enzyme activity in plants after 0.025 mM SNP treatment. Differentially expressed transcripts were analysed in S. polyrrhiza after 0.025 mM SNP treatment. A total of 2776 differentially expressed genes (1425 upregulated and 1351 downregulated) were identified. The expression of some genes related to flavonoid biosynthesis and NO biosynthesis was upregulated, while the expression of some photosynthesis-related genes was downregulated. Moreover, SNP stress also significantly influenced the expression of transcription factors (TFs), such as ERF, BHLH, NAC, and WRKY TFs.ConclusionsTaken together, these findings provide novel insights into the mechanisms of underlying the SNP stress response in S. polyrrhiza and show that the metabolic flux of fixed CO2 is redirected into the starch synthesis and flavonoid biosynthesis pathways after SNP treatment.

Unraveling the dynamics of starch metabolism and expression profiles of starch synthesis genes in millet under drought stress

Drought impacts global food production, prompting extensive research to understand drought tolerance in millet. However, knowledge regarding the extent of tolerance achievable through acclimation remains limited. The objective of the study is to assess the effect of drought acclimation (hardening) on drought tolerance in millet and to investigate the physiological, biochemical, and transcriptional changes associated with starch metabolism in millet. To achieve this aim, two millet genotypes (‘PI 689680’ and ‘PI 662292’), exhibiting differential responses to drought stress, were subjected to various treatments: control (unstressed), drought acclimation (DA; two stress episodes with recovery), and non-acclimation (NA; a single stress episode with no recovery).. The study revealed that drought-induced oxidative stress, manifested by increased amylose, amylopectin, and total starch accumulation in NA plants compared to DA counterparts. Additionally, NA plants experienced a notable reduction in growth and photosynthetic activity. Expression patterns of starch-related transcripts were relatively elevated in NA compared to DA plants. These findings highlighted that acclimation to drought conferred tolerance to subsequent stress events by mitigating oxidative damage induced by drought stress. DA plants exhibited improved tolerance, characterized by enhanced growth, net photosynthetic rate, stomatal activity, osmotic adjustment, starch accumulation, enzyme activity, and the regulated expression of related genes. The study advocates for adopting acclimation as a strategic approach to mitigate the adverse effects of metabolic disruptions induced by drought in millet.

Integrated Bioinformatics and Multi-Omics Analyses Reveal Possible Molecular Mechanisms for Seed Starch Content Differences between Glycine max and Cicer arietinum

Although soybean and chickpea belong to the legume family, their seed starch content is very different. Currently, many studies focus on the molecular mechanisms of starch synthesis within a single species. However, the key genes and regulatory relationships responsible for the difference in seed starch content between the two species remain unknown. To elucidate the molecular mechanisms responsible for the above difference, multi-omics and bioinformatics analyses were used here to analyze gene expression patterns, protein–protein interaction networks, gene-transcription factor co-expression networks, and miRNA–gene regulatory relationships based on reported sucrose and starch metabolic genes in Arabidopsis. The results were as follows. First, seven differential expression genes of the two species in starch synthesis metabolism, including GBSS1, APL3, APS1, SS2, PTST, SBE2, and ISA, and the starch degradation gene BMY in soybean and chickpea, may contribute to their seed starch content differences. Then, the protein–protein interaction between DPEs and PHS may facilitate seed starch synthesis in chickpea. Finally, the positive regulation of two starch degradation genes (GmBMY and GmPHS) and four sucrose metabolism genes (GmHXK, GmPFK, GmTPS, and GmFRK) by transcription factors may lead to lower seed starch content in soybean. This study elucidates the possible molecular mechanisms underlying the difference in seed starch content between the two species and addresses the scientific problem of why soybean seeds have lower starch content than chickpea seeds.