Starch Synthesis Research Articles

Molecular Mechanisms of Poplar Adaptation to Water–Fertilizer Coupling: Insights from Transcriptomic and Metabolomic Analyses

The aim of this paper was to investigate the transcriptomic and metabolomic differences in Populus cathayana × canadasis ‘Xinlin1’ (P. cathayana × canadasis ‘Xinlin 1’) under varying irrigation and fertilization conditions. Ten-year-old P. cathayana × canadasis ‘Xinlin 1’ was selected as the test subject in this study; different irrigation and fertilization treatments were set up, and DEGs and DAMs in response to water and fertilizer regulation were identified. Transcriptomic and metabolomic profiles were analyzed from both leaves and roots. A total of 22,870 DEGs were identified in response to water and fertilizer treatments, predominantly belonging to 48 transcription factor families, including MYB, ERF, and MYB-related ones. Additionally, 2432 DAMs were detected and categorized into 18 metabolite classes, with flavonoids being the most abundant (342 metabolites), followed by terpenoids, lipids, and others. KEGG enrichment analysis revealed that DEGs and DAMs were significantly associated with pathways such as plant hormone signal transduction and starch and sucrose metabolism pathways. The levels of ABA exhibited an initial decrease followed by an increase, with several key genes, including PYR/PYL, PP2C, SnRK2, and ABF, also differentially expressed in the plant hormone signal transduction pathway. In the starch and sucrose metabolic pathways, sucrose was more hydrolyzed into D-fructose, which gradually translocated from roots to leaves. DEGs were significantly involved in sucrose synthesis and decomposition into D-fructose and 1,3-β-glucose, as well as starch synthesis and starch decomposition into cellulose dextrin, which underwent complete hydrolysis to glucose. In the starch hydrolysis process, 29 DEGs were involved, with 12 down-regulated and 17 up-regulated.

Transcriptome-Based Spatiotemporal Analysis of Drought Response Mechanisms in Two Distinct Peanut Cultivars

Drought tolerance varies among different peanut (Arachis hypogaea L.) cultivars. Here, drought responses of two cultivars, Huayu 22 (HY22) with drought tolerance and Fuhua 18 (FH18) with drought sensitivity, were compared at the morphological, physiological, biochemical, photosynthetic, and transcriptional levels. Drought stress caused wilting and curling of leaves, bending of stems, and water loss in both cultivars. There was an increase in malondialdehyde (MDA) content under prolonged drought stress, more so in FH18. But the levels of reactive oxygen species (H2O2) and lipid peroxidation were low in HY22. The activities of superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) were considerably elevated, corresponding with rapid increases in the accumulation of soluble proteins, soluble sugars, and proline. Transcriptional sequencing showed gene expression varied seriously in HY22, which was upregulated in both stems of two cultivars, though downregulation was less pronounced in HY22. KEGG pathway analysis revealed significant enrichment in four leaf and six stem pathways. Additionally, core genes relating to photosynthesis, carbon fixation, proline synthesis, and sucrose and starch synthesis pathways were identified by correlation analysis. Those gene expressions were variously upregulated in stems of two cultivars, especially in HY22, giving a novel view of the shoot as a whole participating in stress response.

Changes in SWEET-mediated sugar partitioning affect photosynthesis performance and plant response to drought.

Sugars, produced through photosynthesis, are at the core of all organic compounds synthesized and used for plant growth and their response to environmental changes. Their production, transport, and utilization are highly regulated and integrated throughout the plant life cycle. The maintenance of sugar partitioning between the different subcellular compartments and between cells is important in adjusting the photosynthesis performance and response to abiotic constraints. We investigated the consequences of the disruption of four genes coding for SWEET sugar transporters in Arabidopsis (SWEET11, SWEET12, SWEET16, and SWEET17) on plant photosynthesis and the response to drought. Our results show that mutations in both SWEET11 and SWEET12 genes lead to an increase of cytosolic sugars in mesophyll cells and phloem parenchyma cells, which impacts several photosynthesis-related parameters. Further, our results suggest that in the swt11swt12 double mutant, the sucrose-induced feedback mechanism on stomatal closure is poorly efficient. On the other hand, changes in fructose partitioning in mesophyll and vascular cells, measured in the swt16swt17 double mutant, positively impact gas exchanges, probably through an increased starch synthesis together with higher vacuolar sugar storage. Finally, we propose that the impaired sugar partitioning, rather than the total amount of sugars observed in the quadruple mutant, is responsible for the enhanced sensitivity upon drought. This work highlights the importance of considering SWEET-mediated sugar partitioning rather than global sugar content in photosynthesis performance and plant response to drought. Such knowledge will pave the way to design new strategies to maintain plant productivity in a challenging environment.

Genome-Wide Association Study of Sweet Potato Storage Root Traits Using GWASpoly, a Gene Dosage-Sensitive Model.

Sweet potato (Ipomoea batatas) is an important food crop that plays a pivotal role in preserving worldwide food security. Due to its polyploid genome, high heterogeneity, and phenotypic plasticity, sweet potato genetic characterization and breeding is challenging. Genome-wide association studies (GWASs) can provide important resources for breeders to improve breeding efficiency and effectiveness. GWASpoly was used to identify 28 single nucleotide polymorphisms (SNPs), comprising 21 unique genetic loci, associated with sweet potato storage root traits including dry matter (4 loci), subjective flesh color (5 loci), flesh hue angle (3 loci), and subjective skin color and skin hue angle (9 loci), in 384 accessions from the USDA sweet potato germplasm collection. The I. batatas 'Beauregard' and I. trifida reference genomes were utilized to identify candidate genes located within 100 kb from the SNPs that may affect the storage traits of dry matter, flesh color, and skin color. These candidate genes include transcription factors (especially Myb, bHLH, and WRKY family members), metabolite transporters, and metabolic enzymes and associated proteins involved in starch, carotenoid, and anthocyanin synthesis. A greater understanding of the genetic loci underlying sweet potato storage root traits will enable marker-assisted breeding of new varieties with desired traits. This study not only reinforces previous research findings on genes associated with dry matter and β-carotene content but also introduces novel genetic loci linked to these traits as well as other root characteristics.

Whole genome sequencing of Castanea mollissima and molecular mechanisms of sugar and starch synthesis.

The chestnut tree exhibits self-incompatibility, where the selection of the male parent (pollen xenia) significantly affects seed starch metabolism, as well as fruit yield and quality. Despite its importance, the molecular mechanisms underlying pollen xenia remains largely unknown. In this study, we utilized the 'Lan You' variety of C. mollissima to construct a high-quality reference genome. As a result, a first Telomere-to-telomere (T2T) gap-free genome for this species was successfully assembled. A total of 560 transcription factors and 22 structural genes were identified as consistent across the TO-GCNs, indicating a consistent regulation pattern in the co-expression of genes involved in starch accumulation. These networks were further divided into three sub-networks: T1, T2, and T3. Among these, the T1 and T2 sub-networks exhibited a higher number of structural genes with consistent regulation patterns and were closely associated with sugar biosynthesis. The gene SBE (Camol08G0254600) was identified as the hub gene with the highest degree of connectivity, encoding a key rate-limiting enzyme in the amylopectin biosynthesis pathway. This study provides a foundation for further research on C. mollissima population genetics, genetic improvement, and strategies aimed at enhancing yield and quality.

Transcriptome analysis reveals regulatory mechanism of postharvest softening in kiwiberry

BackgroundKiwiberry is an emerging edible fruit with market potential owing to its advantages of small size, thin and hairless skin, and sweet taste. However, kiwiberry is highly susceptible to softening after harvest, which poses a challenge for storage and transport. To reveal the underlying cause of kiwiberry softening, it is essential to investigate the characteristics of postharvest fruit and the molecular mechanisms that affect changes in fruit firmness.ResultsMorphological observations and analysis of physical parameters showed that the skin of kiwiberry did not change markedly from the 1st to the 7th day after harvest, while the colour of the inner pericarp gradually turned yellow. By the 9th day of room temperature storage, the kiwiberries began to rot. The hardness decreased rapidly from the 1st to the 5th day postharvest, reaching the low level on the 5th day. The starch and pectin contents of kiwiberry showed a downward trend with increasing storage time. Transcriptome sequencing and weighted gene co-expression network analysis identified 29 key genes associated with the changes in the hardness of kiwiberry after harvest. Gene Ontology enrichment analysis indicated that these 29 genes are mainly involved in pectin metabolism, starch synthesis, starch decomposition, and starch metabolism. In addition, three transcription factors, AGL31, HAT14, and ALC, were identified to be strongly positively correlated with the 29 genes that affect the hardness changes of kiwiberry after harvest, and 28 of the 29 key genes were predicted to be regulated by HAT14.ConclusionsThese results reveal the changes in morphological characteristics and physiological indicators during the postharvest ripening and softening of kiwiberry stored under room temperature conditions. Transcriptome analysis identified 29 key genes and three transcription factors that affect the firmness changes of postharvest kiwiberry. The results of this study thus provide insight into the transcriptional regulatory mechanism of kiwiberry softening during storage to improve the postharvest quality.

Green synthesis of silver, starch, and zinc oxide mediated nanoparticles with probiotics and plant extracts, their characterization and anti-bacterial activity

Nanotechnology has various applications in all branches of science, including engineering, medicine, pharmacy, and other related fields. Conventional techniques, such as the chemical reduction approach, which produces nanoparticles (NPs) using various hazardous chemicals, offer several health risks due to their toxicity and raise serious environmental concerns. In contrast, other techniques are expensive and need a lot of energy. More than 70 % of pathogenic bacterial strains have developed resistance to at least one class of antibiotics, leading to an increase in life-threatening bacterial infections that pose a significant health risk. However, the creation of NPs by biogenic synthesis is risk-free for the environment and clean enough for biological use. This study was aimed at synthesis of novel Moringa oleifera mediated starch capped silver-zinc NPs and green synthesis of ZnO nanoparticles from Aloe vera, papaya, and Lactobacillus plantarum. Antimicrobial activity of both NPs was tested against Gram-negative antibiotic-resistant bacteria Pseudomonas aeruginosa, Gram-positive bacteria Staphylococcus aureus (ATCC 6538), and two foodborne pathogens Listeria monocytogenes and Campylobacter jejuni. Ultraviolet–visible spectroscopy, Fourier Transform Infrared Spectroscopy, and Scanning Electron Microscopy were used for characterization. Majority of the research studies stress the flexibility, repeatability, and desirable features of the metals, polymers, and plant components employed in the production of biomedical nanoparticles. Such an intuitive approach provides several advantages, particularly a reasonable total expense, compliance with healthcare and pharmaceutical implementations, and the ability to produce massive volumes for industrial use. The novelty of the presented work lies in the unusual combination of silver, starch, and zinc oxide nanoparticles using Moringa oleifera, which is an eco-friendly alternative to chemical-based methods. This research exhibits the formation of well-defined nanoparticles with strong antibacterial activity against a wide range of pathogens, giving us insights into their potential applications in various biomedical fields.

Exploring the synergistic effects of drought and heat stress on chickpea seed development: Insights into nutritional quality and seed yield

Growing chickpea (Cicer arietinum L.) faces significant challenges due to rising temperatures and drought stress, particularly during the reproductive and seed-filling phases. This study investigated the single and joint impacts of drought and heat stress on seed development, focusing on the responses of drought-tolerant (DT) and drought-sensitive (DS) chickpea genotypes. Initially raised in an outdoor environment (mean day and night temperature of 27 and 16±1 °C, respectively, light intensity of 1230–1440 µmol m−2s−1, relative humidity of 70/43 %) until seed filling (around 110–113 days after sowing) commenced. The plants were subsequently exposed to single or combined heat and drought stress under controlled conditions until maturity. Control pots were maintained at day and night temperature of 25 and 15 °C, respectively with 500 µmol m−2s−1 light, 60–65 % RH, and regular irrigation, and drought-stressed pots were kept at 50 % field capacity under the same conditions of light and humidity. Heat stress in pots was gradually increased to 32(day)/20 °C (night) under regular irrigation, while combined stress pots experienced both drought (50 % field capacity) and heat stress conditions 32(day)/20 °C (night) under the same light and humidity conditions with irrigation. All stress treatments adversely affected cell membranes, photosynthesis, and water regulation, with more pronounced effects under combined stress. While heat stress increased stomatal conductance, drought and combined stress significantly reduced it. Seed filling rate and duration decreased under all stress conditions, especially combined stress. The stresses in combination severely reduced seed weight and pod numbers compared to individual stresses. Enzyme activities involved in starch and sucrose synthesis and hydrolysis substantially decreased under the combined stress. Seed composition elements (starch, storage proteins, sugars, fat, crude fiber, and ash) exhibited significant reductions across all stress treatments, particularly for the combined stress. Thus, under combined stresses, starch, proteins, and soulube sugars were markedly decreased to 13–20 %, 6.4–12.4 %, and 3–5 % in seeds, compared to 37–39 %, 21–24 %, and 6 % in control seeds. The DT genotype outperformed the DS genotype for all traits under individual and combined stress conditions. Principal component analysis revealed a complex interplay among various physiological responses (membrane damage, chlorophyll, chlorophyll fluorescence, relative leaf water content, and stomatal conductance), seed yield, and seed composition under the combined stress. This study highlighted that combined heat and drought stress severely impacted chickpea yield and nutritional traits, such as seed starch and protein content, compared to individual stresses underscoring the need to develop cultivars tolerant to this stress combination.

Modulation of the Arabidopsis Starch Metabolic Network by the Cytosolic Acetyl-CoA Pathway in the Context of the Diurnal Illumination Cycle

The starch metabolic network was investigated in relation to other metabolic processes by examining a mutant with altered single-gene expression of ATP citrate lyase (ACL), an enzyme responsible for generating cytosolic acetyl-CoA pool from citrate. Previous research has shown that transgenic antisense plants with reduced ACL activity accumulate abnormally enlarged starch granules. In this study, we explored the underlying molecular mechanisms linking cytosolic acetyl-CoA generation and starch metabolism under short-day photoperiods. We performed transcriptome and quantification of starch accumulation in the leaves of wild-type and antisense seedlings with reduced ACL activity. The antisense-ACLA mutant accumulated more starch than the wild type under short-day conditions. Zymogram analyses were conducted to compare the activities of starch-metabolizing enzymes with transcriptomic changes in the seedling. Differential expression between wild-type and antisense-ACLA plants was detected in genes implicated in starch and acetyl-CoA metabolism, and cell wall metabolism. These analyses revealed a strong correlation between the transcript levels of genes responsible for starch synthesis and degradation, reflecting coordinated regulation at the transcriptomic level. Furthermore, our data provide novel insights into the regulatory links between cytosolic acetyl-CoA metabolism and starch metabolic pathways.

Increased sugar content impairs pollen fertility and reduces seed-setting in high-photosynthetic-efficiency rice

Crop yield depends on biomass, which is primarily associated with photosynthesis. We previously demonstrated that two photorespiratory bypasses, i.e., GOC (glycolate oxidase + oxalate oxidase + catalase) and GCGT (glycolate oxidase + catalase + glyoxylate carboligase + tartronic semialdehyde reductase), significantly increased photosynthesis, biomass, and grain yield, but decreased seed-setting rates in rice. This study explored the underlying mechanism of how elevated photosynthetic efficiency impacted the seed-setting. First, pollen germination assessed in vivo and in vitro, revealed a reduced germination rate in GCGT rice. Subsequent analysis found that photosynthates highly accumulated in the leaves and stems; sucrose and soluble sugar levels were increased but the starch level was reduced in the anthers. Uridine diphosphate glucose (UDP-Glc) was increased but uridine diphosphate galactose (UDP-Gal) was unaltered, thus causing an imbalance in the UDP-Glc/UDP-Gal ratio in GCGT anthers. Most anthers in GCGT plants had two locules in contrast to four in the wild-type (WT). Pollen tapetum was developmentally abnormal, and genes related to sucrose synthesis, transport, and tapetal programmed cell death (PCD) were upregulated, whereas those involved in starch synthesis and conversion were downregulated in GCGT anthers. Taken together, our results demonstrated that an increase in sugar content was the primary factor causing reduced seed-setting rates in high photosynthetic efficiency rice, during which metabolic disorder of sugars and UDP sugar imbalance in anthers lead to impaired pollen fertility.

Mutation of MeMinD increased amyloplast size with a changed starch granule morphologenesis and structures in cassava storage roots

Amyloplasts are the sites of starch synthesis and accumulation. Little is known about amyloplast division and its effects on the size, structure, and physicochemical properties of starch granules. In this study, we created mutants of plastid division-related gene MeMinD by CRISPR/Cas9 technology, leading to the disruption of normal division of amyloplasts in cassava storage roots. The memind mutants exhibited significantly enlarged amyloplasts with an increased number of starch granules, and broader range of granule sizes. The loss of MeMinD function led to transcriptional reprogramming of gene expressions related to starch-synthesizing enzymes, affecting the fine structure of starch. Starch in memind mutant storage roots showed a significantly decreased proportion of shorter amylopectin chains and an increased proportion of medium and long chains, which ultimately led to a significant increase in apparent amylose content (AAC) in memind mutants compared to that in WT. The changes in starch granule size and structure resulted in a significant increase in onset temperature (To), peak temperature (Tp), and conclusion temperature (Tc) of the gelatinization process, extending the time to reach peak temperature. These data suggest that regulating amyloplast division affects starch accumulation in cassava, presenting an effective strategy for developing novel cassava starch.

Editing of the soluble starch synthase gene MeSSIII-1 enhanced the amylose and resistant starch contents in cassava

Foods with high amylose and resistant starch (RS) contents have great potential to enhance human health. In this study, cassava soluble starch synthase MeSSIII-1 gene mutants were generated using CRISPR/Cas9 system. The results showed that the storage roots of messiii-1 mutants had higher contents of amylose, RS, and total starch than those in CK. The rates of small and large-sized starch granules were increased. Additionally, amylopectin starch in messiii-1 mutants had a higher proportion of medium- and long- chains, and a lower proportion of short-chains than those in CK. The onset, peak, and conclusion temperatures of starch gelatinization in messiii-1 mutants were significantly lower than those in CK, and the peak viscosity, trough viscosity and final viscosity all increased. MeSSIII-1 mutation could increase the contents of sucrose, glucose, and fructose in cassava storage roots. We hypothesize that these soluble sugars serve a dual role: they provide the necessary carbon source for starch synthesis and act as sugar signals to trigger the transcriptional reprogramming of genes involved in starch biosynthesis. This process results in a collective enhancement of amylose, RS, and total starch contents, accompanied by changes in starch granule morphology, fine structure, and physicochemical properties.

Incomplete filling in the basal region of maize endosperm: timing of development of starch synthesis and cell vitality.

Starch synthesis in maize endosperm adheres to the basipetal sequence from the apex downwards. However, the mechanism underlying nonuniformity among regions of the endosperm in starch accumulation and its significance is poorly understood. Here, we examined the spatiotemporal transcriptomes and starch accumulation dynamics in apical (AE), middle (ME), and basal (BE) regions of endosperm throughout the filling stage. Results demonstrated that the BE had lower levels of gene transcripts and enzymes facilitating starch synthesis, corresponding to incomplete starch storage at maturity, compared with AE and ME. Contrarily, the BE showed abundant gene expression for genetic processing and slow progress in physiological development (quantified by an index calculated from the expression values of development progress marker genes), revealing a sustained cell vitality of the BE. Further analysis demonstrated a significant parabolic correlation between starch synthesis and physiological development. An in-depth examination showed that the BE had more active signaling pathways of IAA and ABA than the AE throughout the filling stage, while ethylene showed the opposite pattern. Besides, SNF1-related protein kinase1 (SnRK1) activity, a regulator for starch synthesis modulated by trehalose-6-phosphate (T6P) signaling, was kept at a lower level in the BE than the AE and ME, corresponding to the distinct gene expression in the T6P pathway in starch synthesis regulation. Collectively, the findings support an improved understanding of the timing of starch synthesis and cell vitality in regions of the endosperm during development, and potential regulation from hormone signaling and T6P/SnRK1 signaling.

Differences in Physicochemical Properties of Stems in Oat (Avena sativa L.) Varieties with Distinct Lodging Resistance and Their Regulation of Lodging at Different Planting Densities.

Planting density is an effective strategy for regulating both oat lodging and forage quality. To delve into the regulatory mechanisms of planting density on lodging and oat forage quality, lodging-resistant variety LENA and lodging-sensitive variety QY2 were grown in 2018 and 2019 growing seasons, and four planting densities were implemented: 2.25 × 106 plants/ha (D1), 4.5 × 106 plants/ha (D2), 6.75 × 106 plants/ha (D3), and 9 × 106 plants/ha (D4). At the milk stage, we measured the contents of potassium, calcium, magnesium, silicon, lignin, crude fiber, starch, soluble sugar, and soluble protein in the second and third stem internodes of the plants. The results revealed the lodging-resistant variety LENA demonstrated significantly higher contents of calcium, potassium, silicon, crude fiber, lignin, and lower contents of starch, soluble sugar, and soluble protein (p < 0.01). Similar trends in the physicochemical properties of stem internodes for both oat varieties with increasing planting density. Crude fiber, soluble sugar, magnesium, starch, potassium, and lignin were the key characteristics affecting the lodging coefficient, and variety and planting density affected the lodging coefficient mainly by regulating the synthesis of starch, soluble sugar, and crude fiber. At planting density D3, stem internodes exhibited higher physicochemical properties and a lower lodging coefficient, favoring oat forage production. The results offer a valuable theoretical foundation and practical reference for oat lodging-resistant cultivation.

Effects of Low Field Temperature on the Physicochemical Properties and Fine Structure Stability of High-Quality Rice Starch during the Grain Filling Stage.

The consumption of high-quality rice is increasing. Low temperatures during grain filling may affect the starch synthesis of high-quality rice and thus affect the quality of the rice itself. In this study, two high-quality conventional rice cultivars and two high-quality hybrid rice cultivars were selected and sown at a low temperature and normal temperature in the field. The low temperature during grain filling increased the amylose content, final viscosity, setback, short amylopectin chain ratio, and degree of amylopectin branching in four high-quality rice cultivars; meanwhile, the amylopectin content, gelatinization temperature, proportion of medium-long chain amylopectin, and the short-range order of starch decreased. Compared with the normal temperature, the alterations in the physicochemical and structural qualities of high-quality conventional rice cultivars YZX and NX42 were less significant at lower temperatures. The starch quality of high-quality conventional rice was more stable than hybrid high-quality rice.

Starch-related structural basis and enzymatic mechanism of the different appearances of soft rice

To investigate the fine starch structure characteristics and formation mechanism of high-quality appearance soft rice, two high-quality and low-quality soft rice varieties (HA-SR and LA-SR, respectively) were selected. Differences in appearance quality, fine starch structure, and activity of key enzymes involved in starch synthesis during the grain-filling stage were compared. The results showed that compared with LA-SR, HA-SR were less chalky, more transparent, had larger starch grains, a lower content of shorter chains (DP 6–24), a higher content of longer chains (DP ≥ 25), lower relative crystallinity, fewer ordered structures, more amorphous structures and larger thicknesses of semi-crystalline lamellae. In terms of amylase activity during the grain-filling stage, the AGPase and GBSS activities of HA-SR were higher, and the SBE activity of HA-SR was lower compared to LA-SR. In conclusion, higher AGPase activity can produce a higher filling rate resulting in fuller starch grain in soft rice. Fuller starch grains reduce the chalkiness of soft rice. Higher AGPase and GBSS activities and lower SBE activity can result in soft rice with more long-branched and less short-branched amylopectin. Thus, soft rice has lower relative crystallinity and less ordered structure. These structures may facilitate reduce grain chalkiness and improve grain transparency.

Kinetic and Structural Studies of the Plastidial Solanum tuberosum Phosphorylase.

Kinetics and structural studies of the plastidial Solanum tuberosum phosphorylase (stPho1) revealed that the most active form of the enzyme (stPho1ΔL78) is composed by two segments generated by proteolytic degradation of an approximately 65-residue-long peptide (L78) approximately in the middle of the stPho1 primary structure. stPho1ΔL78 is 1.5 times more active than the nonproteolyzed enzyme in solution and shows stronger specificity for glycogen, α-d-glucose, caffeine, and β-cyclodextrin than stPho1. The crystal structure of stPho1ΔL78 has been resolved at 2.2 Å resolution and revealed similarities and differences with the mammalian enzymes. The structural fold is conserved as is the active site, while other binding sites such as the inhibitor, the glycogen storage, the quercetin, and the allosteric are not. The binding of α-d-glucose, caffeine, and β-cyclodextrin to stPho1 has been studied by X-ray crystallography and revealed significant differences from those of the mammalian phosphorylases. As stPho1 is capable of catalyzing both starch synthesis and degradation, our studies suggest that the direction of stPho1 activity is regulated by the proteolytic degradation of the L78 peptide.

The maltose-related starch degradation pathway promotes the formation of large and spherical transitory starch granules.

Previously, in Arabidopsis thaliana, we found atypical spherical starch granules in dpe2ss4 and dpe2phs1ss4. However, the mechanism of such abnormal morphogenesis is still obscure. By tracking starch granule length and thickness with leaf ageing, we reported that the starch granules in dpe2phs1ss4 gradually change to a spherical shape over time. In comparison, Col-0 and the parental line ss4 did not exhibit macroscopic morphological alteration. In this study, firstly, we specify that the additional lack of DPE2 resulted in the gradual alteration of starch granule morphology over time. Similar gradual morphological alterations were also found in dpe2, mex1, and sex4 but not in the other starch degradation-related mutants, such as sex1-8, pwd, and bam3. The gradual alteration of starch morphology can be eliminated by omitting the dark phase, suggesting that the particular impaired starch degradation in dpe2- and mex1-related mutants influences starch morphology. Secondly, we observed that spherical starch morphology generation was accompanied by prominent elevated short glucan chains of amylopectin and an increased amylose proportion. Thirdly, the interplay between soluble starch synthase 2 and branching enzymes was affected and resulted in the formation of spherical starch granules. The resulting spherical starch granules allow for elevated starch synthesis efficiency. Fourthly, the starch phosphate content at the granule surface correlated with the morphology alteration of the starch granules. Herewith, we propose a model that spherical starch granules, accumulated in mutants with a misbalance of the starch degradation pathway, are result of elevated starch synthesis to cope with overloaded carbohydrates.

Water and Fertilizer Management Is an Important Way to Synergistically Enhance the Yield, Rice Quality and Lodging Resistance of Hybrid Rice.

This study comprehensively investigated the synergistic effects and underlying mechanisms of optimized water and fertilizer management on the yield, quality, and lodging resistance of hybrid rice (Oryza sativa), through a two-year field experiment. Two hybrid rice varieties, Xinxiangliangyou 1751 (XXLY1751) and Yueliangyou Meixiang Xinzhan (YLYMXXZ), were subjected to three irrigation methods (W1: wet irrigation, W2: flooding irrigation, W3: shallow-wet-dry irrigation) and four nitrogen fertilizer treatments (F1 to F4 with application rates of 0, 180, 225, and 270 kg ha-1, respectively). Our results revealed that the W1F3 treatment significantly enhanced photosynthetic efficiency and non-structural carbohydrate (NSC) accumulation, laying a robust foundation for high yield and quality. NSC accumulation not only supported rice growth but also directly influenced starch and protein synthesis, ensuring smooth grain filling and significantly improving yield and quality. Moreover, NSC strengthened stem fullness and thickness, converting them into structural carbohydrates such as cellulose and lignin, which substantially increased stem mechanical strength and lodging resistance. Statistical analysis demonstrated that water and fertilizer treatments had significant main and interactive effects on photosynthetic rate, dry matter accumulation, yield, quality parameters, NSC, cellulose, lignin, and stem bending resistance. This study reveals the intricate relationship between water and fertilizer management and NSC dynamics, providing valuable theoretical and practical insights for high-yield and high-quality cultivation of hybrid rice, significantly contributing to the sustainable development of modern agriculture.

Lysine 98 in NAC20/NAC26 transcription factors: a key regulator of starch and protein synthesis in rice endosperm

Starch and proteins are main storage product to determine the appearance, cooking, texture, and nutritional quality of rice (Oryza sativa L.). OsNAC20 and OsNAC26, as pivotal transcription factors, redundantly regulate the expression of genes responsible for starch and protein synthesis in the rice endosperm. Any knockout of OsNAC20 or OsNAC26 did not result in visible endosperm defects. In this study, we had isolated and characterized a mutant named as floury endosperm25 (flo25). The caryopsis of the flo25 mutant exhibits a floury endosperm, accompanied by reductions in both the 1000-grain weight and grain length, as well as diminished levels of total starch and protein. Through map-based cloning, it was determined that FLO25 encodes a NAM, ATAF, and CUC (NAC) transcription factors, namely OsNAC26, with a lysine to asparagine substitution at position 98 in the flo25 mutant. Remarkably, lysine 98 is conserved across plants species, and this mutation does not alter the subcellular localization of OsNAC26 but significantly attenuates its transcriptional activity and its ability to activate downstream target genes. Furthermore, the mutant protein encoded by OsNAC26-flo25 could interact with OsNAC20, disrupting the native interaction between OsNAC20 proteins. Additionally, when lysine 98 is substituted with asparagine in OsNAC20, the resulting mutant protein, OsNAC20(K98N), similarly disrupts the interaction between OsNAC26 proteins. Collectively, these findings underscore the pivotal role of Lysine 98 (K) in modulating the transcriptional activity of NAC20/NAC26 within the rice endosperm.