Beta-amylase Gene Research Articles

Comprehensive Identification of the β-Amylase (BAM) Gene Family in Response to Cold Stress in White Clover.

White clover (Trifolium repens L.) is an allopolyploid plant and an excellent perennial legume forage. However, white clover is subjected to various stresses during its growth, with cold stress being one of the major limiting factors affecting its growth and development. Beta-amylase (BAM) is an important starch-hydrolyzing enzyme that plays a significant role in starch degradation and responses to environmental stress. In this study, 21 members of the BAM gene family were identified in the white clover genome. A phylogenetic analysis using BAMs from Arabidopsis divided TrBAMs into four groups based on sequence similarity. Through analysis of conserved motifs, gene duplication, synteny analysis, and cis-acting elements, a deeper understanding of the structure and evolution of TrBAMs in white clover was gained. Additionally, a gene regulatory network (GRN) containing TrBAMs was constructed; gene ontology (GO) annotation analysis revealed close interactions between TrBAMs and AMY (α-amylase) and DPE (4-alpha-glucanotransferase). To determine the function of TrBAMs under various tissues and stresses, RNA-seq datasets were analyzed, showing that most TrBAMs were significantly upregulated in response to biotic and abiotic stresses and the highest expression in leaves. These results were validated through qRT-PCR experiments, indicating their involvement in multiple gene regulatory pathways responding to cold stress. This study provides new insights into the structure, evolution, and function of the white clover BAM gene family, laying the foundation for further exploration of the functional mechanisms through which TrBAMs respond to cold stress.

Multi-omics analysis reveals improvement of tomato quality by grafting on goji rootstock

Abstract Background Tomato quality is a complex trait influenced by multiple genes involved in various complicated metabolic pathways. Materials and Methods This study sought to improve tomato taste and quality by grafting on goji rootstock. We integrated physiological and biochemical indicators, as well as metabolic and transcriptomic analysis, to evaluate tomato quality. Results The grafted tomatoes showed significant increases in soluble solids (51.48%), vitamin C (16.86%), soluble protein (16.19%), titratable acid (11.73%), anthocyanin (11.43%), and polysaccharide (9.43%) content compared to those of the control. Metabolomics analysis identified 234 differentially accumulated metabolites and transcriptome analysis identified 4213 differentially expressed genes between grafted and control tomatoes at three ripening stages (mature green, turning, and fully red). A total of 93 phenolic compounds, including flavonoids and phenolic acids, showed differential accumulation patterns between grafted and control tomatoes at the fully red stage. These changes were attributed to the upregulation of key genes (F3ʹH, F3ʹ5ʹH, DFR, and ANS) associated with flavonoids and anthocyanin synthesis in the goji rootstock compared to those of the control. The expression of genes involved in sucrose hydrolysis and starch synthesis, including invertase (INV), sucrase synthase (SUS), and beta-amylase (BAM) genes, were suppressed by goji grafting, resulting in increased levels of sugars. In addition, the consistency between the transcriptomic and metabolomic data provided a robust validation of the observed quality changes. Conclusions Taken together, our results demonstrate that grafting onto goji rootstock improves tomato quality by modulating multiple genes involved in phenylpropanoid, sucrose, and starch pathways during fruit development, providing valuable insights for improving the quality and taste of tomato.

Study on the Flower Induction Mechanism of Hydrangea macrophylla.

The flower induction of Hydrangea macrophylla "Endless Summer" is regulated by a complex gene network that involves multiple signaling pathways to ensure continuous flowering throughout the growing season, but the molecular determinants of flower induction are not yet clear. In this study, genes potentially involved in signaling pathway mediating the regulatory mechanism of flower induction were identified through the transcriptomic profiles, and a hypothetical model for this regulatory mechanism was obtained by an analysis of the available transcriptomic data, suggesting that sugar-, hormone-, and flowering-related genes participated in the flower induction process of H. macrophylla "Endless Summer". The expression profiles of the genes involved in the biosynthesis and metabolism of sugar showed that the beta-amylase gene BAM1 displayed a high expression level at the BS2 stage and implied the hydrolysis of starch. It may be a signaling molecule that promotes the transition from vegetative growth to reproductive growth in H. macrophylla "Endless Summer". Complex hormone regulatory networks involved in abscisic acid (ABA), auxin (IAA), zeatin nucleoside (ZR), and gibberellin (GA) also induced flower formation in H. macrophylla. ABA participated in flower induction by regulating flowering genes. The high content of IAA and the high expression level of the auxin influx carrier gene LAX5 at the BS2 stage suggested that the flow of auxin between sources and sinks in H. macrophylla is involved in the regulation of floral induction as a signal. In addition, flowering-related genes were mainly involved in the photoperiodic pathway, the aging pathway, and the gibberellin pathway. As a result, multiple pathways, including the photoperiodic pathway, the aging pathway, and the gibberellin pathway, which were mainly mediated by crosstalk between sugar and hormone signals, regulated the molecular network involved in flower induction in H. macrophylla "Endless Summer".

Comparative analysis of the transcriptome during single-seed formation of Castanea henryi: regulation of starch metabolism and endogenous hormones

BackgroundIn seed plants, the ovule is the precursor to the seed. The process of ovule development and differentiation is regulated by multiple factors, including starch metabolism and endogenous hormones. Castanea henryi produces nuts with high nutritional value. However, the high proportion of empty buds restricts the commercial use of the tree. Previous studies have shown that the empty bud phenotype is closely related to ovule abortion. If none of the ovules in the ovary expand rapidly and develop in 7–8 weeks after pollination, an empty bud will form. Therefore, we studied the development and molecular mechanisms underlying single seed formation in C. henryi.ResultsWe found that 49 days after pollination (DAP) is a critical period for the formation of fertile and abortive ovules. The morphology and starch distribution of the fertile and abortive ovules differed significantly at 49 DAP. The fertile ovules were smooth and round in appearance, with a large amount of starch. In contrast, abortive ovules were smaller with only a small amount of starch. The embryo sac of the abortive ovule proceeded to develop abnormally, and the entire ovule lacked starch. We identified 37 candidate genes involved in metabolism with potential roles in the regulation of starch levels. Three ADP-glucose pyrophosphorylase (AGPase) genes, one granule-bound starch synthase (GBSS) gene, and two beta-amylase genes could affect starch accumulation. The levels of auxin, cytokinins, gibberellins, and jasmonic acid in fertile ovules were higher than those in abortive ovules. In addition, the levels of endogenous abscisic acid and salicylic acid in abortive ovules were higher than those in fertile ovules of the same age, consistent with the expression patterns of genes related to the synthesis of abscisic and salicylic acid and signal transduction. We identified and mapped the differentially expressed genes associated with hormone synthesis and signal transduction.ConclusionsThese results improve our general understanding of the molecular mechanisms underlying single seed development in C. henryi and the phenomenon of empty buds, providing directions for future research.

In silico characterization and comparison of the fruit ripening related beta‐ amylase (BAM) gene family in banana genome A and B

Banana is one of the most important commodities for maintaining global food security. Primary metabolic processes during the ripening of banana greatly affect post‐harvest quality, particularly in starch metabolism. The beta‐ amylase (BAM) gene family is known as a group of genes that plays an important role in starch metabolism regulation. In this study, we focused on the characterization and comparative analysis of the BAM gene family in DH Pahang and Pisang Klutuk Wulung (PKW) varieties, these being the AA and BB genomes, respectively. The sequences of BAM gene family were retrieved from the database of Musa acuminata ’DH Pahang’ and Musa balbisiana ’PKW’ genome, then structural and functional characterization was performed, followed by identification of cis‐acting elements in the BAM promoter regions. The results showed that the BAM gene family structure was relatively conserved in both genomes, and a putative BAM11 gene was found, the function of which has not been studied in other plants. Cis‐acting element analysis showed that they were distinct in the copy number and types of elements that were responsive to various phytohormones. This study suggested that the BAM genes involved in ripening are spatiotemporally regulated. However, further functional genomic analysis is required to describe the specific role and regulation of BAM genes during ripening in banana.

Analysis of β-amylase gene (Amyβ) variation reveals allele association with low enzyme activity and increased firmness in cooked sweetpotato (Ipomoea batatas) from East Africa.

β-amylase is a thermostable enzyme that hydrolyses starch during cooking of sweetpotato (Ipomoea batatas) storage roots, thereby influencing eating quality. Its activity is known to vary amongst genotypes but the genetic diversity of the beta-amylase gene (Amyβ) is not well studied. Amyβ has a highly conserved region between exon V and VI, forming part of the enzyme's active site. To determine the gene diversity, a 2.3 kb fragment, including the conserved region of the Amyβ gene was sequenced from 25 sweetpotato genotypes. The effect of sequence variation on gene expression, enzyme activity, and firmness in cooked roots was determined. Six genotypes carrying several SNPs within exon V, linked with an AT or ATGATA insertion in intron V were unique and clustered together. The genotypes also shared an A336E substitution in the amino acid sequence, eight residues upstream of a substrate-binding Thr344. The genotypes carrying this allele exhibited low gene expression and low enzyme activity. Enzyme activity was negatively correlated with firmness (R = −0.42) in cooked roots. This is the first report of such an allele, associated with low enzyme activity. These results suggest that genetic variation within the AmyB locus can be utilized to develop markers for firmness in sweetpotato breeding.

The AaCBF4-AaBAM3.1 module enhances freezing tolerance of kiwifruit (Actinidia arguta)

Beta-amylase (BAM) plays an important role in plant resistance to cold stress. However, the specific role of the BAM gene in freezing tolerance is poorly understood. In this study, we demonstrated that a cold-responsive gene module was involved in the freezing tolerance of kiwifruit. In this module, the expression of AaBAM3.1, which encodes a functional protein, was induced by cold stress. AaBAM3.1-overexpressing kiwifruit lines showed increased freezing tolerance, and the heterologous overexpression of AaBAM3.1 in Arabidopsis thaliana resulted in a similar phenotype. The results of promoter GUS activity and cis-element analyses predicted AaCBF4 to be an upstream transcription factor that could regulate AaBAM3.1 expression. Further investigation of protein-DNA interactions by using yeast one-hybrid, GUS coexpression, and dual luciferase reporter assays confirmed that AaCBF4 directly regulated AaBAM3.1 expression. In addition, the expression of both AaBAM3.1 and AaCBF4 in kiwifruit responded positively to cold stress. Hence, we conclude that the AaCBF-AaBAM module is involved in the positive regulation of the freezing tolerance of kiwifruit.

Genome-wide association studies for waxy starch in cassava

Cassava (Manihot esculenta Crantz) is an important crop for starch production, and recently much effort has been directed towards improving its starch properties. Waxy cassava starch has some advantages over starch from other sources due to its neutral flavor and pasting properties. The genetic inheritance of the waxy starch phenotype is considered to be monogenic and recessive; however, it is possible that other genomic regions contribute to the waxy phenotype. The aim of this study was to evaluate the power of genome-wide association studies (GWAS) to detect variants related to waxy starch and to identify alternative genes or genomic regions. For this purpose, a set of 382 samples (waxy and non-waxy) was analyzed using a panel of 20,956 single nucleotide polymorphisms (SNPs). All genotypes were evaluated in relation to the presence of waxy starch, determined using the 2% iodine test. The GWAS was performed using the retrospective CAse–control Retrospective Association Testing (CARAT) model. Kinship and population structure were also investigated and added to the model. Ten SNPs were found to be significant and located on chromosome 2 and co-located in genomic regions. The significant SNPs are in a region near the Granule-bound starch synthase I (GBSSI) and Beta-amylase genes. Additive and epistatic effects were also found among the significant SNPs, and these need to be better investigated in segregant populations of waxy sources. The regions and genes identified in this work may drive further studies and reveal biological processes related to the waxy phenotype.

Expression patterns of alpha-amylase and beta-amylase genes provide insights into the molecular mechanisms underlying the responses of tea plants (Camellia sinensis) to stress and postharvest processing treatments.

The alpha-amylase and beta-amylase genes have been identified from tea plants, and their bioinformatic characteristics and expression patterns provide a foundation for further studies to elucidate their biological functions. Alpha-amylase (AMY)- and beta-amylase (BAM)-mediated starch degradation plays central roles in carbohydrate metabolism and participates extensively in the regulation of a wide range of biological processes, including growth, development and stress response. However, the AMY and BAM genes in tea plants (Camellia sinensis) are poorly understood, and the biological functions of these genes remain to be elucidated. In this study, three CsAMY and nine CsBAM genes from tea plants were identified based on genomic and transcriptomic database analyses, and the genes were subjected to comprehensive bioinformatic characterization. Phylogenetic analysis showed that the CsAMY proteins could be clustered into three different subfamilies, and nine CsBAM proteins could be classified into four groups. Putative catalytically active proteins were identified based on multiple sequence alignments, and the tertiary structures of these proteins were analyzed. Cis-element analysis indicated that CsAMY and CsBAM were extensively involved in tea plant growth, development and stress response. In addition, the CsAMY and CsBAM genes were differentially expressed in various tissues and were regulated by stress treatments (e.g., ABA, cold, drought and salt stress), and the expression patterns of these genes were associated with the postharvest withering and rotation processes. Taken together, our results will enhance the understanding of the roles of the CsAMY and CsBAM gene families in the growth, development and stress response of tea plants and of the potential functions of these genes in determining tea quality during the postharvest processing of tea leaves.

The wild sweetpotato (Ipomoea trifida) genome provides insights into storage root development

BackgroundSweetpotato (Ipomoea batatas (L.) Lam.) is the seventh most important crop in the world and is mainly cultivated for its underground storage root (SR). The genetic studies of this species have been hindered by a lack of high-quality reference sequence due to its complex genome structure. Diploid Ipomoea trifida is the closest relative and putative progenitor of sweetpotato, which is considered a model species for sweetpotato, including genetic, cytological, and physiological analyses.ResultsHere, we generated the chromosome-scale genome sequence of SR-forming diploid I. trifida var. Y22 with high heterozygosity (2.20%). Although the chromosome-based synteny analysis revealed that the I. trifida shared conserved karyotype with Ipomoea nil after the separation, I. trifida had a much smaller genome than I. nil due to more efficient eliminations of LTR-retrotransposons and lack of species-specific amplification bursts of LTR-RTs. A comparison with four non-SR-forming species showed that the evolution of the beta-amylase gene family may be related to SR formation. We further investigated the relationship of the key gene BMY11 (with identity 47.12% to beta-amylase 1) with this important agronomic trait by both gene expression profiling and quantitative trait locus (QTL) mapping. And combining SR morphology and structure, gene expression profiling and qPCR results, we deduced that the products of the activity of BMY11 in splitting starch granules and be recycled to synthesize larger granules, contributing to starch accumulation and SR swelling. Moreover, we found the expression pattern of BMY11, sporamin proteins and the key genes involved in carbohydrate metabolism and stele lignification were similar to that of sweetpotato during the SR development.ConclusionsWe constructed the high-quality genome reference of the highly heterozygous I. trifida through a combined approach and this genome enables a better resolution of the genomics feature and genome evolutions of this species. Sweetpotato SR development genes can be identified in I. trifida and these genes perform similar functions and patterns, showed that the diploid I. trifida var. Y22 with typical SR could be considered an ideal model for the studies of sweetpotato SR development.

Low-temperature conditioning combined with cold storage inducing rapid sweetening of sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) while inhibiting chilling injury

Sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) are prone to chilling injury (CI) when stored at low temperature. Here, tuberous roots were subjected to low-temperature conditioning (LTC) at 10 °C for 5 d before exposure to chilling stress under cold storage at 4 °C for 28 d. After investigation of antioxidant and sugar metabolic responses to chilling stress, the results indicated that LTC treatment can enhance sweetness while effectively reducing CI observed in roots stored at 4 °C for 28 d. Moreover, LTC triggered increased sucrose levels, transcription of enzyme genes, and increased superoxide dismutase, catalase, and ascorbate peroxidase activities, while preventing increases in malondialdehyde content, relative leakage, and production of reactive oxygen species during cold storage. Furthermore, LTC may trigger beta-amylase gene transcription via C-repeat binding factor (CBF) pathway induction. Therefore, LTC combined with cold storage can induce fast sweetening in tuberous roots while preventing chilling injury.

Functional analysis of a grape WRKY30 gene in drought resistance

WRKY transcription factors constitute a large protein family in plants and take part in a variety of stress response processes, such as drought resistance. In this study, the drought resistant function of a WRKY transcription factor gene WRKY30 from a wine grape cultivar ‘Vidal Blanc’ was investigated. Quantitative real-time PCR (qRT-PCR) analysis indicated that the expression of VvWRKY30 was induced by drought stress and stress response related signal molecules, such as abscisic acid (ABA), nitric oxide and salicylic acid. Phenotypic analysis of transgenic Arabidopsis indicated that over-expression of VvWRKY30 conferred increased drought resistance, demonstrated by enhancements in seed germination rate and root development, as well as a decrease in water loss and stomatal aperture under drought conditions. In further study, we found that VvWRKY30 resistance to drought occurred mainly by promoting the expression of regulators of an ABA-dependent and independent signal pathway. Over-expression of VvWRKY30 also up-regulated the expressions of proline synthetase gene P5CS1, sucrose synthase gene SS4, beta-amylase gene BAM4, glucose-6-phosphate dehydrogenase gene G6PDH, and antioxidant enzyme synthesis genes Cu/ZnSOD, CAT2 and POD2. The content of proline and soluble sugar, as well as the activities of superoxide dismutase, peroxidase, and catalase were increased. Overall, our results demonstrate that VvWRKY30 positively regulates drought response by regulating ABA signal pathway, modulating proline and soluble sugar metabolism, as well as activating the scavenging systems of reactive oxygen species.

Beta-amylase gene variability in introgressive wheat lines.

Variability of the beta-amylase gene in bread wheat, artificial amphidiploids, and derived introgression wheat lines was analyzed. Variation in homeologous beta-amylase sequences caused by the presence of MITE (Miniature Inverted-Repeat Transposable Element) and its footprint has been identified in bread wheat. The previously unknown location of MITE in Triticum urartu and T. aestivum L. beta-amylase gene has been found. These species have a MITE sequence in the third intron of beta-amylase, as opposed to Aegilops comosa and a number of other Triticeae species, which have it in the fourth intron. These two MITEs from Ae. comosa and T. aestivum were shown to have low identity scores. Miosa, an artificial amphidiploid, which has the M genome from Ae. comosa was shown to lose the MITE sequences. This loss might be caused by genomic shock due to allopolyploidization.

Effects of cold acclimation on sugar metabolism and sugar-related gene expression in tea plant during the winter season.

Sugar plays an essential role in plant cold acclimation (CA), but the interaction between CA and sugar remains unclear in tea plants. In this study, during the whole winter season, we investigated the variations of sugar contents and the expression of a large number of sugar-related genes in tea leaves. Results indicated that cold tolerance of tea plant was improved with the development of CA during early winter season. At this stage, starch was dramatically degraded, whereas the content of total sugars and several specific sugars including sucrose, glucose and fructose were constantly elevated. Beyond the CA stage, the content of starch was maintained at a low level during winter hardiness (WH) period and then was elevated during de-acclimation (DC) period. Conversely, the content of sugar reached a peak at WH stage followed by a decrease during DC stage. Moreover, gene expression results showed that, during CA period, sugar metabolism-related genes exhibited different expression pattern, in which beta-amylase gene (CsBAM), invertase gene (CsINV5) and raffinose synthase gene (CsRS2) engaged in starch, sucrose and raffinose metabolism respectively were solidly up-regulated; the expressions of sugar transporters were stimulated in general except the down-regulations of CsSWEET2, 3, 16, CsERD6.7 and CsINT2; interestingly, the sugar-signaling related CsHXK3 and CsHXK2 had opposite expression patterns at the early stage of CA. These provided comprehensive insight into the effects of CA on carbohydrates indicating that sugar accumulation contributes to tea plant cold tolerance during winter season, and a simply model of sugar regulation in response to cold stimuli is proposed.

Evolution of the beta-amylase gene in the temperate grasses: Non-purifying selection, recombination, semiparalogy, homeology and phylogenetic signal

Low-copy nuclear genes (LCNGs) have complex genetic architectures and evolutionary dynamics. However, unlike multicopy nuclear genes, LCNGs are rarely subject to gene conversion or concerted evolution, and they have higher mutation rates than organellar or nuclear ribosomal DNA markers, so they have great potential for improving the robustness of phylogenetic reconstructions at all taxonomic levels. In this study, our first objective is to evaluate the evolutionary dynamics of the LCNG β-amylase by testing for potential pseudogenization, paralogy, homeology, recombination, and phylogenetic incongruence within a broad representation of the main Pooideae lineages. Our second objective is to determine whether β-amylase shows sufficient phylogenetic signal to reconstruct the evolutionary history of the Pooid grasses. A multigenic (ITS, matK, ndhF, trnTL, and trnLF) tree of the study group provided a framework for assessing the β-amylase phylogeny. Eight accessions showed complete absence of selection, suggesting putative pseudogenic copies or other relaxed selection pressures; resolution of Vulpia alopecuros 2x clones indicated its potential (semi) paralogy; and homeologous copies of allopolyploid species Festuca simensis, F. fenas, and F. arundinacea tracked their Mediterranean origin. Two recombination events were found within early-diverged Pooideae lineages, and five within the PACCMAD clade. The unexpected phylogenetic relationships of 37 grass species (26% of the sampled species) highlight the frequent occurrence of non-treelike evolutionary events, so this LCNG should be used with caution as a phylogenetic marker. However, once the pitfalls are identified and removed, the phylogenetic reconstruction of the grasses based on the β-amylase exon+intron positions is optimal at all taxonomic levels.

Allelic variants of the gene bamy1 barley in Eastern European and Central Asian areas

The collections of varieties of spring barley cultivars from the Eastern European and Central Asian areas were analyzed by exonpecific PCR (EPIC) for beta-amylase genes. The endosperm beta-amylase gene (bamyl) was differentiated by the presence of 126 bp MITE insertion into intron 3 that is associated with low activity beta-amylase. The findings suggest that a low level of genetic variation for bamylgene within climatic zones is associated with individual breeding program for each climatic zone.

Lotus Cell Walls and the Genes Involved in its Synthesis and Modification

The lotus genome (Nelumbo nucifera (Gaertn.)) lacks the paleo-triplication found in other eudicots and has evolved remarkably slowly with fewer nucleotide mutations. It is thought to have greater retention of duplicated genes than other angiosperms. We evaluated the potential genes involved in cell wall synthesis and its modification, and ethylene synthesis and response. In many cell wall transferases and hydrolases families, lotus had fewer members in most families when compared to Arabidopsis. Lotus had similar or fewer members in each family as found in poplar, grape and papaya. The exceptions were in the sialyl and beta-glucuronsyl transferases where similar number were found as in the core eudicots. Lotus had similar numbers of polygalacturonase and pectin methyl esterases as found in Arabidopsis but fewer in all other hydrolases families. For starch degradation, lotus had only two alpha amylases predicted genes versus eight to ten in other eudicots, with similar numbers of beta amylase genes predicted. Lotus also had less than half the number of genes predicted for the enzymes involved in lignin and tannin synthesis compared to Arabidopsis. The stress plant growth regulator ethylene’s synthesis, reception and response predicted genes were fewer in lotus than other eudicots. Only two ethylene receptor genes were predicted in lotus with five reported for Arabidopsis and six for tomato. Our analysis does not supports the conclusion that this species has greater retention of duplicated genes though our data does support the conclusion that lotus split occurred at the base of the eudicots.

イネ茎葉部のデンプン代謝におけるβ-アミラーゼ遺伝子, OsBAM2の役割

イネ茎葉部のデンプン代謝におけるβ-アミラーゼ遺伝子, OsBAM2の役割

Expression of an engineered granule-boundEscherichia coliglycogen branching enzyme in potato results in severe morphological changes in starch granules

The Escherichia coli glycogen branching enzyme (GLGB) was fused to either the C- or N-terminus of a starch-binding domain (SBD) and expressed in two potato genetic backgrounds: the amylose-free mutant (amf) and an amylose-containing line (Kardal). Regardless of background or construct used, a large amount of GLGB/SBD fusion protein was accumulated inside the starch granules, however, without an increase in branching. The presence of GLGB/SBD fusion proteins resulted in altered morphology of the starch granules in both genetic backgrounds. In the amf genetic background, the starch granules showed both amalgamated granules and porous starch granules, whereas in Kardal background, the starch granules showed an irregular rough surface. The altered starch granules in both amf and Kardal backgrounds were visible from the initial stage of potato tuber development. High-throughput transcriptomic analysis showed that expression of GLGB/SBD fusion protein in potato tubers did not affect the expression level of most genes directly involved in the starch biosynthesis except for the up-regulation of a beta-amylase gene in Kardal background. The beta-amylase protein could be responsible for the degradation of the extra branches potentially introduced by GLGB.

Importance of ABA homeostasis under terminal drought stress in regulating grain filling events

Recent studies suggest that abscisic acid (ABA) at its basal level plays an important role during seed set and grain filling events. Under drought stress ABA levels were found to be significantly enhanced in the developing seed. Until now we lack an understanding of (A) ABA homeostasis in developing seeds under terminal drought and (B) the interactive role of ABA in regulating the starch biosynthesis pathway in developing grains under terminal drought. We have recently reported the possible regulation of ABA homeostasis in source (flag leaf) and sink (developing grains) tissues under post-anthesis drought stress in barley and concluded that significantly enhanced ABA levels in developing grains are due to strong activation of the ABA deconjugation pathway and fine regulation of the ABA biosynthesis-degradation pathway.1 Additionally, we provided evidence for the role of ABA in differential regulation of starch biosynthesis genes and a significant upregulation of starch degradation beta amylase genes under drought, i.e. ABA not only influences the rate of starch accumulation but also starch quality.