Starch Biosynthesis Pathway Research Articles

A metabolic roadmap of waxy corn flavor

As well as being a popular vegetable crop worldwide, waxy corn represents an important amylopectin source. However, little is known about the breeding history and flavor characteristics of this crop. In this study, comparative-omic analyses between 318 diverse waxy corn and 507 representative field corn inbred lines revealed that many metabolic pathways and genes exhibited characteristics of selection during the breeding history of waxy corn, contributing to the divergence between waxy and field corn. We show that waxy corn is not only altered in its glutinous property, but that sweetness, aroma, and palatability are all significantly affected. A substantial proportion (43%) of flavor-related metabolites have pleiotropic effects, impacting both flavor and yield characteristics and 27% of these metabolites are related to antagonistic outcomes on yield and flavor. Furthermore, we demonstrated, through multiple concrete examples, how yield and quality are coordinately or antagonistically regulated at the genetic level. In particular, we identified some sweet molecules such as DIMBOA and raffinose, that do not participate in the starch biosynthesis pathway, as potential targets for breeding a new type of “sweet-waxy” corn. Our findings shed light on the historical selection of waxy corn and demonstrate the genetic and metabolic basis of waxy corn flavor, thereby collectively providing valuable resources and knowledge for future crop breeding for improved nutritional quality.

Preparation of Barley AGPS2b Antibody and Its Application in Hormone Regulation Research

ADP-glucose pyrophosphorylase (AGPase), which is a key enzyme in the starch biosynthesis pathway, plays a critical role in barley grain development. Despite its importance, the regulatory mechanisms governing AGPase expression, particularly the influence of plant hormones, remain poorly understood in barley. To address this, we identified and characterized the HvAGPS2b gene, which encodes the AGPase small subunit. The full-length HvAGPS2b gene was cloned from the barley database and expressed as a recombinant protein using the pET-30a system. Polyclonal antibodies were prepared against HvAGPS2b to facilitate detailed analysis. Our findings revealed that HvAGPS2b, as a small subunit of the rate-limiting enzyme AGPase, is integral to the later stages of grain development. Furthermore, RT-qPCR and Western blotting analyses showed that the phytohormones ABA, GA, ETH, and BR significantly upregulated the expression of AGPase small subunits. These results underscore the vital role of plant hormones in modulating AGPS2b expression, thereby influencing grain development. This study provides significant insights into the hormonal regulation of starch biosynthesis and establishes a foundation for further investigation into the functional dynamics of AGPase in barley.

Protein kinase MeSnRK2.3 positively regulates starch biosynthesis by interacting with the transcription factor MebHLH68 in cassava.

Starch biosynthesis involves numerous enzymes and is a crucial metabolic activity in plant storage organs. Sucrose non-fermenting related protein kinase 2 (SnRK2) is an abscisic acid (ABA)-dependent kinase and a significant regulatory enzyme in the ABA signaling pathway. However, whether SnRK2 kinases regulate starch biosynthesis is unclear. In this study, we identified that MeSnRK2.3, an ABA-dependent kinase, was highly expressed in the storage roots of cassava and was induced by ABA. Overexpression of MeSnRK2.3 in cassava significantly increased the starch content in the storage roots and promoted plant growth. MeSnRK2.3 was further found to interact with the cassava basic helix-loop-helix 68 (MebHLH68) transcription factor in vivo and in vitro. MebHLH68 directly bound to the promoters of sucrose synthase 1 (MeSUS1), granule-bound starch synthase I a (MeGBSSIa), and starch-branching enzyme 2.4 (MeSBE2.4), thereby upregulating their transcriptional activities. Additionally, MebHLH68 negatively regulated the transcriptional activity of sucrose phosphate synthase B (MeSPSB). Moreover, phosphorylated MebHLH68 by MeSnRK2.3 up-regulated the transcription activity of MeSBE2.4. These findings demonstrated that the MeSnRK2.3-MebHLH68 module connects the ABA signaling pathway and starch biosynthesis in cassava, thereby providing direct evidence of ABA-mediated participation in the sucrose metabolism and starch biosynthesis pathway.

ADP-glucose pyrophosphorylase gene family in soybean and implications in drought stress tolerance.

ADP-glucose pyrophosphorylase (AGPase) is the key rate-limiting enzyme in starch biosynthesis pathway, and has been identified as a potential target for manipulation strategies aimed at improving crop yield and quality. To identify the AGPase gene family members in soybean, and explore the potential implications of GmAGPS2 in drought stress tolerance. Thegenome-wide identification and sequence analysis of soybean AGPase gene family was carried out by bioinformatics methods. The GmAGP gene expression was analyzed using transcriptome data and quantitative real-time PCR (qRT-PCR). Furthermore, transgenic yeast strains overexpressing GmAGPS2 were generated, and their growth was observed under drought stress. In this study, we searched for AGPase genes (GmAGP) in the soybean genome and identified a total of 14 GmAGP genes. The GmAGP proteins had a unique conserved NTP_transferase domain and were mainly located in the chloroplast and cytosol. Evolutionarily, theGmAGP proteins can be clustered into two distinct subgroups; within the same subgroup, they displayed a similar distribution pattern of conserved motifs. The GmAGP genes exhibited an uneven distribution on 10 chromosomes, and segmental duplication contributed to AGPase gene family expansion in soybean. The GmAGP genes presented different tissue expression pattern, in which GmAGPL6, GmAGPL9, and GmAGPL10 mainly exhibited tissue-specific expression pattern. The promoter of GmAGP genes had multiple cis-acting elements related to phytohormones and stress responses, and 8 GmAGP genes contained drought-responsive cis-acting elements. qRT‒PCR analysis demonstrated a significant upregulation expression of GmAGPL6, GmAGPL10, and GmAGPS2 in response to drought stress. Further functional analysis indicated that GmAGPS2 gene could improve yeast growth under drought stress conditions and enhance the drought tolerance of yeast. These results will contribute to further elucidation of the function of GmAGP genes, and offer important candidate genes for the genetic improvement of starch and yield-related traits and the breeding of high drought stress tolerance varieties in soybean.

In-Silico Identification, Characterization and Expression Analysis of Genes Involved in Resistant Starch Biosynthesis in Potato (Solanum tuberosum L.) Varieties.

Potato (Solanum tuberosum L.), an important horticultural crop is a member of the family Solanaceae and is mainly grown for consumption at global level. Starch, the principal component of tubers, is one of the significant elements for food and non-food-based applications. The genes associated with biosynthesis of starch have been investigated extensively over the last few decades. However, a complete regulation pathway of constituent of amylose and amylopectin are still not deeply explored. The current in-silico study of genes related to amylose and amylopectin synthesis and their genomic organization in potato is still lacking. In the current study, the nucleotide and amino acid arrangement in genome and twenty-two genes linked to starch biosynthesis pathway in potato were analysed. The genomic structure analysis was also performed to find out the structural pattern and phylogenetic relationship of genes. The genome mining and structure analysis identified ten specific motifs and phylogenetic analysis of starch biosynthesis genes divided them into three different clades on the basis of their functioning and phylogeny. Quantitative real-time PCR (qRT-PCR) of amylose biosynthesis pathway genes in three contrast genotypes revealed the down-gene expression that leads to identify potential cultivar for functional genomic approaches. These potential lines may help to achieve higher content of resistant starch.

Unveiling the Benefits of Resistant Starch in Legumes: Overview of Current and Future Prospective

AbstractResistant starch has gained substantial attention in recent years due to its potential health benefits. Among the various sources of RS, legumes have appeared as a prominent and promising contributor. Legumes like beans, lentils, and chickpeas, comprise a unique composition that promotes the resistant starch formation during cooking and processing. The review begins by presenting an overview of resistant starch and its classification based on its structure and digestibility. The mechanisms by which legume‐based resistant starch impacts human health are discussed, including its potential role in controlling postprandial glucose and insulin responses, improve satiety, boost colonic health, and influence lipid metabolism. The promising role of resistant starch from legumes in controlling chronic diseases like obesity, cardiovascular disorders, and type 2 diabetes is also explored. This review briefly covers the recent advancements in regulating the starch biosynthesis pathway through the utilization of RNA interference (RNAi) and CRISPR/Cas9 techniques. In summary, the association between resistant starch and legumes offers a compelling pathway to enhance human health and mitigate the risk of chronic diseases. Legumes as a regular part of the diet can be a viable and effective approach to augment resistant starch intake and harness its potential health‐promoting effects.

Toxicological effects and mechanisms of lithium on growth, photosynthesis and antioxidant system in the freshwater microalga Chromochloris zofingiensis

The growing prevalence of lithium (Li) batteries has drawn public attention to Li as an emerging pollutant. The present study investigates the toxicity of Li+ on Chromochloris zofingiensis, examining physiological, biochemical and omics aspects. Results reveal hormesis effects of Li+ on C. zofingiensis growth. At Li+ concentrations below 5 mg L−1, Li+ can enhance chlorophyll content, mitochondrial activity, and antioxidant capacity, leading to increased dry cell weight and cell number. Conversely, when it exceeded 10 mg L−1, Li+ can reduce chlorophyll content, induce oxidative stress, and disrupt chloroplast and mitochondria structure and function, ultimately impeding cell growth. In addition, under 50 mg L−1 Li+ stress, microalgae optimize absorbed light energy use (increasing Fv/Fm and E TR ) and respond to stress by up-regulating genes in starch and lipid biosynthesis pathways, promoting the accumulation of storage components. Weighted gene co-expression network analysis indicates that peptidylprolyl cis/trans isomerase, GTPase and L-ascorbate oxidase might be the key regulators in response to Li+ stress. This research marks the toxic effects and molecular mechanisms of Li+ on freshwater microalga, which would improve our understanding of Li’s toxicology and contributing to the establishment of Li pollution standards.

Evolutionary and expression analysis of starch synthase genes from Tartary buckwheat revealed the potential function of FtGBSSII‐4 and FtGBSSII‐5 in seed amylose biosynthesis

AbstractThe starch synthase has been identified well as a core enzyme in the starch biosynthesis pathway in monocots. However, only a few starch synthase genes (SSs) are known in dicots. Tartary buckwheat (Fagopyrum tataricum Gaertn.) is one of the dicots‐enriched starch in the seeds, but its starch synthesis pathway remains unclear. Here, 15 SS genes were identified in the Tartary buckwheat genome, including 5 granule‐bound starch synthase (GBSS) and 10 soluble starch synthase (SSS) genes. Evolutionary analysis showed that all FtGBSSs belonged to GBSSII, and its isoforms were more abundant than other dicots due to the segmental duplication events. Expression pattern analysis showed two GBSS genes (FtGBSSII‐4 and FtGBSSII‐5) and three SSS genes (FtSSII‐2, FtSSIII‐1, and FtSSIV‐2) were mainly expressed in seeds, indicating that they may be the dominant isoforms for the starch synthesis in Tartary buckwheat. Besides, 23 transcription factor genes out of 1073 were identified from 17 transcription factor families and highly expressed in seeds. Expression correlation analysis suggested that FtNF‐YB2 may be the promising regulators for FtSSs. These results provide new insights and a theoretical basis for understanding starch synthesis and regulation in Tartary buckwheat and other dicots.

Abscisic Acid Regulates Carbohydrate Metabolism, Redox Homeostasis and Hormonal Regulation to Enhance Cold Tolerance in Spring Barley.

Abscisic acid (ABA) plays a vital role in the induction of low temperature tolerance in plants. To understand the molecular basis of this phenomenon, we performed a proteomic analysis on an ABA-deficit mutant barley (Az34) and its wild type (cv Steptoe) under control conditions (25/18 °C) and after exposure to 0 °C for 24 h. Most of the differentially abundant proteins were involved in the processes of photosynthesis and metabolisms of starch, sucrose, carbon, and glutathione. The chloroplasts in Az34 leaves were more severely damaged, and the decrease in Fv/Fm was larger in Az34 plants compared with WT under low temperature. Under low temperature, Az34 plants possessed significantly higher activities of ADP-glucose pyrophosphorylase, fructokinase, monodehydroascorbate reductase, and three invertases, but lower UDP-glucose pyrophosphorylase activity than WT. In addition, concentrations of proline and soluble protein were lower, while concentration of H2O2 was higher in Az34 plants compared to WT under low temperature. Collectively, the results indicated that ABA deficiency induced modifications in starch and sucrose biosynthesis and sucrolytic pathway and overaccumulation of reactive oxygen species were the main reason for depressed low temperature tolerance in barley, which provide novel insights to the response of barley to low temperature under future climate change.

Genetic Diversification of Starch Branching Enzymes during Maize Domestication and Improvement.

Elucidating the genetic basis of starch pasting and gelatinization properties is crucial for enhancing the quality of maize and its utility as feed and industrial raw material. In maize, ZmSBE genes encode important starch branching enzymes in the starch biosynthesis pathway. In this study, we re-sequenced the genomic sequences of ZmSBEI, ZmSBEIIa, ZmSBEIIb, and ZmSBEIII in three lines called 335 inbred lines, 68 landrace lines, and 32 teosinte lines. Analyses of nucleotide polymorphisms and haplotype diversity revealed differences in the selection patterns of ZmSBEI, ZmSBEIIa, ZmSBEIIb, and ZmSBEIII during maize domestication and improvement. A marker-trait association analysis of inbred lines detected 22 significant loci, including 18 SNPs and 4 indels significantly associated with three maize starch physicochemical properties. The allele frequencies of two variants (SNP17249C and SNP5055G) were examined in three lines. The frequency of SNP17249C in ZmSBEIIb was highest in teosinte lines, followed by landrace lines, and inbred lines, whereas there were no significant differences in the frequency of SNP5055G in ZmSBEIII among the three lines. These results suggest that ZmSBE genes play an important role in the phenotypic variations in the starch physicochemical properties in maize. The genetic variants detected in this study may be used to develop functional markers for improving maize starch quality.

Revisiting maize Brittle endosperm-2 reveals new insights in BETL development and starchy endosperm filling

Rerouting the starch biosynthesis pathway in maize can generate specialty types, like sweet corn and waxy corn, with a drastically increasing global demand. Hence, a fine-tuning of starch metabolism is relevant to create diverse maize cultivars for end-use applications. Here, we characterized a new maize brittle endosperm mutant, referred to as bt1774, which exhibited decreased starch content but a dramatic increase of soluble sugars at maturity. Both endosperm and embryo development was impaired in bt1774 relative to the wild-type (WT), with a prominently arrested basal endosperm transfer layer (BETL). Map-based cloning revealed that BRITTLE ENDOSPERM2 (Bt2), which encodes a small subunit of ADP-glucose pyrophosphorylase (AGPase), is the causal gene for bt1774. A MuA2 element was found to be inserted into intron 2 of Bt2, leading to a severe decrease of its expression, in bt1774. This is in line with the irregular and loosely packed starch granules in the mutant. Transcriptome of endosperm at grain filling stage identified 1,013 differentially expressed genes in bt1774, which were notably enriched in the BETL compartment, including ZmMRP1, Miniature1, MEG1, and BETLs. Gene expression of the canonical starch biosynthesis pathway was marginally disturbed in bt1774. Combined with the residual 60 % of starch in this nearly null mutant of Bt2, this data strongly suggests that an AGPase-independent pathway compensates for starch synthesis in the endosperm. Consistent with the BETL defects, zein accumulation was impaired in bt1774. Co-expression network analysis revealed that Bt2 probably has a role in intracellular signal transduction, besides starch synthesis. Altogether, we propose that Bt2 is likely involved in carbohydrate flux and balance, thus regulating both the BETL development and the starchy endosperm filling.

Biogas effluent treatment by Landoltia punctata for starch biomass production

Due to the high potential of using Landoltia punctata in biogas effluent treatment and starch accumulation, three integrated processes were proposed: (1) bioethanol production from duckweed, (2) biogas production from vinasse, and (3) biogas effluent treatment with sequentially increasing starch-rich duckweed biomass. This recent work focuses only on the third process, which involves the treatment of wastewater from biogas effluent and the production of L. punctata with high starch content. L. punctata showed a significantly higher TKN removal and biomass production than Lemna aequinoctialis. After nine days of wastewater treatment and five days of starch accumulation, L. punctata grew by 4.3 g/m2/day, with 44.4% starch content. NH3, NH4+, and PO43− in the biogas effluent were rapidly utilized in the first three days for L. punctata’s growth. The upregulation of AGPase genes in the starch biosynthesis pathway was observed when the environmental conditions changed in both nutrient starvation and population reduction. Production of starch-rich L. punctata using biogas effluent is a sustainable feedstock for the bioethanol process. Moreover, L. punctata-based stabilization pond is a promising technique for biogas effluent treatment.

Comprehensive transcriptome analysis of different potato cultivars provides insight into early blight disease caused by Alternaria solani

BackgroundEarly blight, caused by the necrotrophic fungal pathogen Alternaria solani, is an economically important disease affecting the tuber yield worldwide. The disease is mainly controlled by chemical plant protection agents. However, over-using these chemicals can lead to the evolution of resistant A. solani strains and is environmentally hazardous. Identifying genetic disease resistance factors is crucial for the sustainable management of early blight but little effort has been diverted in this direction. Therefore, we carried out transcriptome sequencing of the A. solani interaction with different potato cultivars with varying levels of early blight resistance to identify key host genes and pathways in a cultivar-specific manner.ResultsIn this study, we have captured transcriptomes from three different potato cultivars with varying susceptibility to A. solani, namely Magnum Bonum, Désirée, and Kuras, at 18 and 36 h post-infection. We identified many differentially expressed genes (DEGs) between these cultivars, and the number of DEGs increased with susceptibility and infection time. There were 649 transcripts commonly expressed between the potato cultivars and time points, of which 627 and 22 were up- and down-regulated, respectively. Interestingly, overall the up-regulated DEGs were twice in number as compared to down-regulated ones in all the potato cultivars and time points, except Kuras at 36 h post-inoculation. In general, transcription factor families WRKY, ERF, bHLH, MYB, and C2H2 were highly enriched DEGs, of which a significant number were up-regulated. The majority of the key transcripts involved in the jasmonic acid and ethylene biosynthesis pathways were highly up-regulated. Many transcripts involved in the mevalonate (MVA) pathway, isoprenyl-PP, and terpene biosynthesis were also up-regulated across the potato cultivars and time points. Compared to Magnum Bonum and Désirée, multiple components of the photosynthesis machinery, starch biosynthesis and degradation pathway were down-regulated in the most susceptible potato cultivar, Kuras.ConclusionsTranscriptome sequencing identified many differentially expressed genes and pathways, thereby contributing to the improved understanding of the interaction between the potato host and A. solani. The transcription factors identified are attractive targets for genetic modification to improve potato resistance against early blight. The results provide important insights into the molecular events at the early stages of disease development, help to shorten the knowledge gap, and support potato breeding programs for improved early blight disease resistance.

Exploration of Sugar and Starch Metabolic Pathway Crucial for Pollen Fertility in Rice.

Starch is the primary storage carbohydrate in mature pollen grains in many crop plants, including rice. Impaired starch accumulation causes male sterility because of the shortage of energy and building blocks for pollen germination and pollen tube growth. Thus, starch-defective pollen is applicable for inducing male sterility and hybrid rice production. Despite the importance of pollen starch, the details of the starch biosynthesis and breakdown pathway in pollen are still largely unknown. As pollen is isolated from the maternal tissue, photoassimilate transported from leaves must pass through the apoplastic space from the anther to the filial pollen, where it is stored as starch. Several sugar transporters and enzymes are involved in this process, but many are still unknown. Thus, the current review provides possible scenarios for sucrose transport and metabolic pathways that lead to starch biosynthesis and breakdown in rice pollen.

Genome-Wide Identification of DOF Gene Family and the Mechanism Dissection of SbDof21 Regulating Starch Biosynthesis in Sorghum.

Starch is one of the main utilization products of sorghum (Sorghum bicolor L.), the fifth largest cereal crop in the world. Up to now, the regulation mechanism of starch biosynthesis is rarely documented in sorghum. In the present study, we identified 30 genes encoding the C2-C2 zinc finger domain (DOF), with one to three exons in the sorghum genome. The DOF proteins of sorghum were divided into two types according to the results of sequence alignment and evolutionary analysis. Based on gene expressions and co-expression analysis, we identified a regulatory factor, SbDof21, that was located on chromosome 5. SbDof21 contained two exons, encoding a 36.122 kD protein composed of 340 amino acids. SbDof21 co-expressed with 15 genes involved in the sorghum starch biosynthesis pathway, and the Pearson correlation coefficients (PCCs) with 11 genes were greater than 0.9. The results of qRT-PCR assays indicated that SbDof21 is highly expressed in sorghum grains, exhibiting low relative expression levels in the tissues of roots, stems and leaves. SbDOF21 presented as a typical DOF transcription factor (TF) that was localized to the nucleus and possessed transcriptional activation activity. Amino acids at positions 182–231 of SbDOF21 formed an important structure in its activation domain. The results of EMSA showed that SbDOF21 could bind to four tandem repeats of P-Box (TGTAAAG) motifs in vitro, such as its homologous proteins of ZmDOF36, OsPBF and TaPBF. Meanwhile, we also discovered that SbDOF21 could bind and transactivate SbGBSSI, a key gene in sorghum amylose biosynthesis. Collectively, the results of the present study suggest that SbDOF21 acts as an important regulator in sorghum starch biosynthesis, exhibiting potential values for the improvement of starch contents in sorghum.

Profiling of transcriptional regulators associated with starch biosynthesis in sorghum (Sorghum bicolor L.)

Starch presents as the major component of grain endosperm of sorghum (Sorghum bicolor L.) and other cereals, serving as the main energy supplier for both plants and animals, as well as important industrial raw materials of human beings, and was intensively concerned world widely. However, few documents focused on the pathway and transcriptional regulations of starch biosynthesis in sorghum. Here we presented the RNA-sequencing profiles of 20 sorghum tissues at different developmental stages to dissect key genes associated with sorghum starch biosynthesis and potential transcriptional regulations. A total of 1,708 highly expressed genes were detected, namely, 416 in grains, 736 in inflorescence, 73 in the stalk, 215 in the root, and 268 genes in the leaf. Besides, 27 genes encoded key enzymes associated with starch biosynthesis in sorghum were identified, namely, six for ADP-glucose pyrophosphorylase (AGPase), 10 for starch synthases (SSs), four for both starch-branching enzymes (SBE) and starch-debranching enzymes (DBEs), two for starch phosphorylases (SPs), and one for Brittle-1 (BT1). In addition, 65 transcription factors (TFs) that are highly expressed in endosperm were detected to co-express with 16 out of 27 genes, and 90 cis-elements were possessed by all 27 identified genes. Four NAC TFs were cloned, and the further assay results showed that three of them could in vitro bind to the CACGCAA motif within the promoters of SbBt1 and SbGBSSI, two key genes associated with starch biosynthesis in sorghum, functioning in similar ways that reported in other cereals. These results confirmed that sorghum starch biosynthesis might share the same or similar transcriptional regulations documented in other cereals, and provided informative references for further regulatory mechanism dissection of TFs involved in starch biosynthesis in sorghum.

Irrigation water salinity structures the bacterial communities of date palm (Phoenix dactylifera)-associated bulk soil.

The irrigation of date palms (Phoenix dactylifera) with saline groundwater is routinely practiced in the agroecosystems of arid environments because of freshwater scarcity. This leads to salts deposition in topsoil layers and increases soil salinization. However, how different irrigation sources affect soil microbiota is poorly understood. Bulk soil samples were collected from date farms receiving non-saline water and saline groundwater to examine bacterial communities using metabarcoding. Overall, bacterial diversity measures (Shannon diversity index, richness, and evenness) did not vary between irrigation sources. Bacterial communities were structured based on irrigation water sources and were significantly associated with their electrical conductivity. Of 5,155 operational taxonomic units (OTUs), 21.3% were unique to soil irrigated with saline groundwater, 31.5% received non-saline water irrigation, and 47.2% were shared. The Proteobacteria abundance was higher in soil under saline groundwater irrigation while Actinobacteriota abundance was lower. A compositional shift at the genera level was also evident; the abundance of Subgroup_10 and Mycobacterium was higher under saline groundwater irrigation. Mycobacterium was a key indicator of OTU under saline groundwater irrigation while Solirubrobacter was an indicator of non-saline water irrigation. Functional gene analyses showed enrichment of fatty acid, cell wall, and starch biosynthesis pathways in soil under saline groundwater irrigation. These findings provide insights into how “salinity filtering” influences bacterial communities, key taxa, and the potential metabolic function in soil under increasing irrigation water salinities, and have broad implications for arid agroecosystems.

The novel ZmTCP7 transcription factor targets AGPase-encoding gene ZmBt2 to regulate storage starch accumulation in maize.

The process of starch biosynthesis is a major developmental event that affects the final grain yield and quality in maize (Zea mays L.), and transcriptional regulation plays a key role in modulating the expression of the main players in the pathway. ZmBt2, which encodes the small subunits of AGPase, is a rate-controlling gene of the pathway; however, much remains unknown about its transcriptional regulation. Our earlier study identifies a short functional fragment of ZmBt2 promoter (394-bp), and further shows it contains multiple putative cis-acting regulatory elements, demonstrating that several transcription factors may govern ZmBt2 expression. Here, we identified a novel TCP transcription factor (TF), ZmTCP7, that interacted with the functional fragment of the ZmBt2 promoter in a yeast one hybrid screening system. We further showed that ZmTCP7 is a non-autonomous TF targeted to the nucleus and predominantly expressed in maize endosperm. Using promoter deletion analyzes by transient expression in maize endosperm protoplasts combined with electrophoretic mobility shift assays, we found that ZmTCP7 bound to GAACCCCAC elements on the ZmBt2 promoter to suppress its expression. Transgenic overexpression of ZmTCP7 in maize caused a significant repression of ZmBt2 transcription by ~77.58%, resulting in a 21.51% decrease in AGPase activity and a 9.58% reduction in the endosperm starch content of transgenic maize. Moreover, the expressions of ZmBt1, ZmSSI, ZmSSIIa, and ZmSSIIIa were increased, while those of ZmSh2 and ZmSSIV reduced significantly in the endosperm of the transgenic maize. Overall, this study shows that ZmTCP7 functions as a transcriptional repressor of ZmBt2 and a negative regulator of endosperm starch accumulation, providing new insights into the regulatory networks that govern ZmBt2 expression and starch biosynthesis pathway in maize.

Effect of irrigation regimes on starch biosynthesis pathway, cotton (Gossypium hirsutum) yield and in silico analysis of ADP-glucose-pyrophosphorylase

Effect of irrigation regimes on starch biosynthesis pathway, cotton (Gossypium hirsutum) yield and in silico analysis of ADP-glucose-pyrophosphorylase

Post‐anthesis saline‐alkali stress inhibits grain filling by promoting ethylene production and signal transduction

AbstractSaline‐alkali stress is one of the major abiotic stresses that severely affect rice yield. However, the mechanism by which saline‐alkali stress regulates grain filling in rice is still unclear. In this study, Oryza sativa L. spp. Indica cultivar Chaoyou1000 (C1000) was exposed to post‐anthesis saline‐alkali conditions at 6 days after anthesis, which significantly reduced the grain weight by suppressing the accumulation of starch and non‐structural carbohydrates in grains. Further analysis found that 1‐aminocyclopropane‐1‐carboxylate (ACC), a precursor for ethylene, was increased by saline‐alkali treatment. qRT‐PCR results showed that several key genes involved in ethylene biosynthesis, including the OsACS and OsACO genes, were upregulated in saline‐alkali‐treated grains. In addition, genes involved in the ethylene signalling pathway were also induced by saline‐alkali stress. Exogenous ethylene application reduced grain weight and both starch and NSC contents in grains of C1000, suggesting that saline‐alkali‐induced ethylene has a negative effect on grain filling. Furthermore, the gene expression levels of OsSUS, OsAGPL, OsAGPS, OsSSI and OsSSIIIa, which are key genes in the starch biosynthesis pathway, were downregulated in saline‐alkali‐treated grains. In agreement, assays on these enzymes further revealed that saline‐alkali stress decreased the activities of sucrose synthase (SUS), adenosine diphosphate glucose pyrophosphorylase (AGP) and starch synthase (StS). Together, our results indicated that saline‐alkali stress suppressed the enzyme activities involved in the conversion of sucrose to starch by elevating ethylene production, which led to inhibition of grain filling.