Search Results (49)

Grain filling governs grain weight formation in rice, while starch biosynthesis during this process critically determines both grain quality and yield. In this study, we characterized the heading date regulator OsPRR37 on regulating grain development, starch metabolism, and starch physicochemical properties. The osprr37 mutants exhibited undesirable agronomic traits, including reduced plant height, decreased grain thickness, lower 1000-grain weight, and diminished yield. Moreover, mutant endosperm displayed irregular starch packing, aberrant granules morphology, and decreased granule diameter. Impaired grain filling was observed in osprr37 mutants with reduced grain filling rates, which coincided with elevated soluble sugar content and reduced starch accumulation during grain development. Simultaneously, the expression of starch synthesis-related genes (SSRGs) was significantly altered. osprr37 mutants had decreased total starch and amylose content, leading to reduced starch crystallinity, lower structural order degree, and impaired gelatinization properties. Collectively, our results demonstrated that OsPRR37 functions as a key regulator of grain filling and starch biosynthesis, thereby determining starch composition and physicochemical properties that ultimately affect rice quality and yield. Full article

The H9N2 avian influenza virus (AIV) is difficult to prevent and control because of its low pathogenicity and frequent mutation. In a previous study, the HA (hemagglutinin) protein of H9N2 was expressed in a rice endosperm reactor and prepared into a subunit vaccine to immunize chickens and mice, both of which exhibited a good immunity effect. The results of the intermediate tests of the transgenic strains (AIV-1 and AIV-3) showed that the HA gene can be stably expressed. Agronomic traits, such as plant height and number of grains, were significantly optimized in the transgenic strains. Moreover, no exogenous HA genes were found in the leaves of the weeds, and it was initially determined that there was no risk of gene drift. This study provides key technical support for the commercialization of plant subunit vaccines for avian influenza viruses. Full article

The LATERAL ORGAN BOUNDARIES DOMAIN (LBD) gene family encodes plant-specific transcription factors that play vital roles in plant growth, development, and stress responses. Rice (Oryza sativa L.), a staple food for more than half of the world’s population, also serves as an important model organism for monocot functional genomics. In this study, we conducted a comprehensive genomic survey of the OsLBD gene family in Oryza sativa ssp. japonica using the latest genomic sequence data. A total of 35 members of this family were identified through systematic characterization of their gene structures, conserved domains, phylogenetic relationships, and chromosomal distributions. Our analysis indicated that the expansion of OsLBD genes may have resulted mainly from segmental duplication, with these duplicated genes exhibiting diverse evolutionary fates ranging from functional conservation to expression divergence. Phylogenetic analysis further classified the OsLBD genes into two major groups: Class I and Class II. Expression profiling across various developmental stages demonstrated dynamic spatiotemporal regulation, with certain genes exhibiting tissue-specific expression, particularly in reproductive tissues. Furthermore, a comprehensive co-expression analysis of OsLBD genes and their co-regulators revealed multiple modules with tissue-specific roles in pollen cell wall synthesis and endosperm glycogen biosynthesis. Promoter analysis identified several cis-regulatory elements associated with hormone responses, stress adaptation, and developmental processes, consistent with the observed expression patterns under phytohormone treatments. Comparative genomics revealed a higher degree of synteny between rice and barley than between rice and Arabidopsis, highlighting the evolutionary conservation within the Poaceae family. This study provides a foundational framework for understanding the biological functions of OsLBD genes in rice and identifies promising candidate genes involved in vegetative and reproductive growth, development, and stress responses. Full article

The plant cell wall is essential for maintaining cellular structure and regulating physiological processes such as growth and stress tolerance. Cell wall dynamics are largely mediated by cell wall-modifying enzymes, including glycoside hydrolases (GHs). In this study, we explored GH5 family members in Oryza sativa L. and identified 17 genes encoding GH5 proteins, classified into three subfamilies: GH5_7, GH5_11, and GH5_14. Characterization of the GH5_11 protein encoded by the LOC_Os04g40510 gene involved the subcellular localization of a GFP-tagged protein, gene expression analysis during germination, and phenotypic evaluation of transgenic plants. The protein was synthesized through the secretory pathway with expression in seeds, predominantly in the endosperm. Overexpression of LOC_Os04g40510 resulted in altered seed morphology, increased chalkiness, and reduced seed set. Although the overall seed number increased, the seed mass was reduced for the knock-down lines. These data suggest that LOC_Os04g40510 may play a role in fertility and endosperm development. Our findings provide new insights into the biological function of GH5_11 enzymes in rice. Full article

Although the role of OsHY5L2 in promoting photomorphogenic development is well characterized, its function in regulating rice quality is poorly understood. In this study, we found that OsHY5L2 plays an important role in regulating starch metabolism and modulating its fine structure and physicochemical properties. Overexpression of OsHY5L2 significantly reduced the chalky grain rate and degree of chalkiness but dramatically increased the head rice rate. OsHY5L2 was found to negatively regulate the accumulation of starch in rice endosperm by inhibiting starch biosynthesis and promoting starch hydrolysis. Transcriptomic analysis revealed that OsHY5L2 mainly regulated the expression of genes encoding enzymes involved in starch and sucrose metabolism. Moreover, OsHY5L2 overexpression induced the formation of numerous pinhole structures on the surfaces of starch granules. Analysis of the amylopectin chain length distribution showed that overexpression of OsHY5L2 decreased the proportion of ultra-short chains (DP 6–7) and intermediate chains (DP 13–24) of amylopectin while increasing the proportion of short chains (DP 8–12) and long chains (DP 25–36). Further studies demonstrate that OsHY5L2 overexpression altered the pasting properties of rice starch by affecting its multi-level structure and function. The results of this study improve our understanding of the functions of OsHY5L2 in regulating rice quality. Full article

Grain filling is a vital factor influencing both rice grain yield and quality, yet its underlying mechanisms remain poorly understood. In this study, we perform a functional analysis of the grain-filling defective mutant pex1 in rice. pex1 plants produce seeds that are floury, thick-branched, and exhibit a significantly slower grain-filling rate compared to the wild type. Further analysis reveals that the pex1 mutants accumulated more starch in the pericarp but exhibited a defect in starch accumulation in the endosperm during grain filling, indicating an impaired transport of photosynthetic products from the pericarp to the endosperm. Cells within the nucellar projection in the pex1 mutant appear irregular and loose loosely arranged, consistent with defective transfer of assimilates. Expression analysis reveals a downregulation of key grain-filling genes during the filling phase in the pex1 mutant compared to the wild type, which correlates with the reduced grain-filling rate. Subcellular localization suggests that OsPEX1 is associated with the endoplasmic reticulum. Our findings demonstrate that OsPEX1 plays a crucial role in grain filling. Full article

Grain chalkiness is an undesirable trait that significantly compromises rice quality, attracting considerable attention from both consumers and breeders. In this study, we characterized the role of the autophagy-related gene OsATG4b in rice grain development. OsATG4b was predominantly expressed in the endosperm. Compared with wild-type plants, OsATG4b-overexpressing lines exhibited significantly reduced grain chalkiness, whereas OsATG4b knockout mutants displayed a marked increase in chalkiness. Importantly, OsATG4b had no significant effect on other major agronomic traits. Ultrastructure analysis of the endosperm and evaluation of seed storage components revealed that the chalky endosperm in OsATG4b Knockout mutants contained loosely packed starch granules, aberrant protein bodies, and reduced levels of seed storage proteins. Furthermore, gene expression analysis indicated that OsATG4b regulates the expression of genes involved in storage protein biosynthesis. Together, these findings demonstrate that OsATG4b plays a critical regulatory role in determining grain chalkiness in rice. Full article

Seed vigor critically determines sowing performance, while grain quality fundamentally influences commercial value. Elucidating the genetic mechanisms governing these traits is critical for enhancing both seed vigor and grain quality in rice cultivation. Here, we demonstrate that the endosperm-specific gene OsEnS-42 is highly expressed in germinating seeds and developing seeds at the early filling stage. OsEnS-42 is localized in the nucleus and cytoplasm. The seed vigor of OsEnS-42 knockout plants decreased, manifested as decreases in germination rate, seedling length, and root length. In addition, OsEnS-42 knockout plants showed increased chalkiness and amylose content. The transcriptome and physiological indicators showed that OsEnS-42 regulates seed vigor through soluble sugars and redox metabolism, and regulates grain quality via soluble sugars and seed development-related enzymes. Haplotype analysis of OsEnS-42 across global rice germplasm revealed four distinct haplotypes (Hap 1–4) with subspecies-specific distributions. Crucially, accessions with Hap 4 exhibit a lower percentage of grain with chalkiness than accessions with Hap 1 (predominantly indica), enabling marker-assisted introgression to reduce chalkiness without subspecies barriers. Meanwhile, accessions with Hap 2 show lower amylose content, providing targets for specialty rice breeding. Our findings elucidate the pathways through which OsEnS-42 regulates seed vigor and grain quality, and provide new molecular breeding targets for improving seed vigor and grain quality in rice. Full article

Starch is the primary component of the endosperm and plays a crucial role in rice quality. Although the enzymes involved in starch synthesis have been extensively studied, the transcription factors that regulate these enzymes remain largely unknown. Here, we identified a MYB family transcription factor, OsMYBR1, that regulates starch biosynthesis in rice. OsMYBR1 is highly expressed during endosperm development. Mutations of OsMYBR1 result in reduced grain thickness and a decrease in 1000-grain weight. The endosperm of osmybr1 mutants exhibit rounded and loosely packed starch granules, decreased amylose content, altered fine structure of amylopectin, and modified physicochemical properties. The analysis of RT-qPCR showed that the expression of several starch-synthesis enzyme-coding genes (SSEGs), including OsGBSSⅠ, OsAGPL1, OsAGPL2, OsBEⅡb, OsISA1, PHOL, and OsSSⅢa, is altered in osmybr1 mutants. Further experiments indicated that OsMYBR1 directly binds to the promoters of OsGBSSⅠ, OsAGPL1, OsAGPL2, OsISA1, OsBEⅡb, and PHOL, resulting in an increase in the expression of OsGBSSⅠ but a decrease in the expression of OsAGPL2, OsISA1, and OsSSⅢa. In contrast, OsMYBR1-overexpressing endosperm appears normal, with starch granule morphology, increased amylopectin content, and improved alkali spreading value, indicating enhanced rice eating and cooking quality (ECQ). These findings suggest that the overexpression of OsMYBR1 could be a promising strategy for improving rice ECQ. Full article

High quality stands as a pivotal competitive edge in the rice industry. Optimizing amylose content (AC) and the physicochemical properties of endosperm starch by regulating the Wx gene is crucial for enhancing rice grain quality. In this study, we created a novel Wx^b-d25 allele by deleting a 25 bp segment (−26 to −2) within the Wx core promoter using CRISPR/Cas9. Compared with the wild type and the previously reported Wx^b-i1, Wx^b-d25 exhibited no significant changes in agronomic traits. However, its grains displayed temperature-dependent variations in AC and altered transparency and viscosity characteristics, holding the potential to synergistically improve both the eating and cooking quality (ECQ) and appearance quality (AQ) of rice. Further studies demonstrated that this promoter modification, by partially disrupting the transcription initiator, significantly downregulated the original Wx-01 transcript and generated a novel Wx transcript (ONT.7395.1) in Wx^b-d25 grains. Despite its low expression abundance, the ONT.7395.1 transcript could be completely processed into mature Wx mRNA. The combined effects of the dual transcripts resulted in significantly increased Wx gene expression and AC in Wx^b-d25 grains under conventional cultivation conditions. These findings provide a genetic resource and a theoretical foundation for utilizing the Wx^b-d25 allele to improve rice grain quality. Full article

Grain chalkiness adversely affects rice quality, and the positional variation of grain chalkiness within a rice panicle presents a substantial obstacle to quality improvement in China. However, the molecular mechanism underlying this variation is unclear. This study conducted a genetic and physiological analysis of grains situated at distinct positions (upper, middle, and bottom primary branches of the rice panicle, denoted as Y1, Y2, and Y3) within a rice panicle using the Yangdao 6 variety. The results indicated that the percentage of chalky grains (PCG) in Y1 was the highest, i.e., 17.12% and 52.18% higher than that of Y2 and Y3, respectively. Y2 exhibited the highest degree of grain chalkiness (DGC), attributable to its greater area of endosperm chalkiness (AEC) than the others. Y3 demonstrated the lowest PCG and DGC. Additionally, Y1 and Y2 were characterized by lower amylose and protein contents, as well as looser starch granule morphology, in comparison to Y3. Compared with Y3, both the average and maximum filling rates of Y1 and Y2 increased markedly; however, the active filling duration was notably reduced by 7.10 d and 5.56 d, respectively. The analysis of genomic expression levels indicated an enrichment of starch and sucrose metabolism in Y1-vs.-Y2, Y2-vs.-Y3, and Y1-vs.-Y3, with 7 genes (5 up-regulated and 2 down-regulated), 53 genes (12 up-regulated and 41 down-regulated), and 12 genes (2 up-regulated and 10 down-regulated) in the Y1-vs.-Y2, Y2-vs.-Y3, and Y1-vs.-Y3. The majority of these genes were down-regulated, linking metabolic activity to grain filling and contributing to the occurrence of grain chalkiness in rice panicles. In conclusion, the metabolic processes associated with sucrose and starch play a crucial role in regulating grain filling and the formation of chalkiness in rice. Full article

Heat shock proteins (Hsps), acting as molecular chaperones, play a pivotal role in plant responses to environmental stress. In this study, we found a total of 192 genes encoding Hsps, which are distributed across all 12 chromosomes, with higher concentrations on chromosomes 1, 2, 3, and 5. These Hsps can be divided into six subfamilies (sHsp, Hsp40, Hsp60, Hsp70, Hsp90, and Hsp100) based on molecular weight and homology. Expression pattern data indicated that these Hsp genes can be categorized into three groups: generally high expression in almost all tissues, high tissue-specific expression, and low expression in all tissues. Further analysis of 15 representative genes found that the expression of 14 Hsp genes was upregulated by high temperatures. Subcellular localization analysis revealed seven proteins localized to the endoplasmic reticulum, while others localized to the mitochondria, chloroplasts, and nucleus. We successfully obtained the knockout mutants of above 15 Hsps by the CRISPR/Cas9 gene editing system. Under natural high-temperature conditions, the mutants of eight Hsps showed reduced yield mainly due to the seed setting rate or grain weight. Moreover, the rice quality of most of these mutants also changed, including increased grain chalkiness, decreased amylose content, and elevated total protein content, and the expressions of starch metabolism-related genes in the endosperm of these mutants were disturbed compared to the wild type under natural high-temperature conditions. In conclusion, our study provided new insights into the HSP gene family and found that it plays an important role in the formation of rice quality and yield. Full article

Carotenoid cleavage oxygenases (CCOs) cleave carotenoid molecules to produce bioactive products that influence the synthesis of hormones such as abscisic acid (ABA) and strigolactones (SL), which regulate plant growth, development, and stress adaptation. Here, to explore the molecular characteristics of all members of the OsCCO family in rice, fourteen OsCCO family genes were identified in the genome-wide study. The results revealed that the OsCCO family included one OsNCED and four OsCCD subfamilies. The OsCCO family was phylogenetically close to members of the maize ZmCCO family and the Sorghum SbCCO family. A collinearity relationship was observed between OsNCED3 and OsNCED5 in rice, as well as OsCCD7 and OsNCED5 between rice and Arabidopsis, Sorghum, and maize. OsCCD4a and OsCCD7 were the key members in the protein interaction network of the OsCCO family, which was involved in the catabolic processes of carotenoids and terpenoid compounds. miRNAs targeting OsCCO family members were mostly involved in the abiotic stress response, and RNA-seq data further confirmed the molecular properties of OsCCO family genes in response to abiotic stress and hormone induction. qRT-PCR analysis showed the differential expression patterns of OsCCO members across various rice organs. Notably, OsCCD1 showed relatively high expression levels in all organs except for ripening seeds and endosperm. OsNCED2a, OsNCED3, OsCCD1, OsCCD4a, OsCCD7, OsCCD8a, and OsCCD8e were potentially involved in plant growth and differentiation. Meanwhile, OsNCED2a, OsNCED2b, OsNCED5, OsCCD8b, and OsCCD8d were associated with reproductive organ development, flowering, and seed formation. OsNCED3, OsCCD4b, OsCCD4c, OsCCD8b, and OsCCD8c were related to assimilate transport and seed maturation. These findings provide a theoretical basis for further functional analysis of the OsCCO family. Full article

The composition and distribution of storage substances in rice endosperm directly affect grain quality. A floury endosperm mutant, wcr (white-core rice), was identified, exhibiting a loose arrangement of starch granules with a floury opaque appearance in the inner layer of mature grains, resulting in reduced grain weight. The total starch and amylose content remained unchanged, but the levels of the four component proteins in the mutant brown rice significantly decreased. Additionally, the milled rice (inner endosperm) showed a significant decrease in total starch and amylose content, accompanied by a nearly threefold increase in albumin content. The swelling capacity of mutant starch was reduced, and its chain length distribution was altered. The target gene was mapped on chromosome 5 within a 65 kb region. A frameshift mutation occurred due to an insertion of an extra C base in the second exon of the cyOsPPDKB gene, which encodes pyruvate phosphate dikinase. Expression analysis revealed that wcr not only affected genes involved in starch metabolism but also downregulated expression levels of genes associated with storage protein synthesis. Overall, wcr plays a crucial role as a regulator factor influencing protein synthesis and starch metabolism in rice grains. Full article

High temperatures accelerate the accumulation of storage material in seeds, often leading to defects in grain filling. However, the mechanisms regulating grain filling at high temperatures remain unknown. Here, we want to explore the quality factors influenced by the environment and have identified a LATE EMBROYGENESIS ABUNDANT gene, OsLEA1b, a heat-stress-responsive gene in rice grain filling. OsLEA1b is highly expressed in the endosperm, and its coding protein localizes to the nucleus and cytoplasm. Knock-out mutants of OsLEA1b had abnormal compound starch granules in endosperm cells and chalky endosperm with significantly decreased grain weight and grain number per panicle. The oslea1b mutants exhibited a lower proportion of short starch chains with degrees of polymerization values from 6 to 13 and a higher proportion of chains with degrees from 14 to 48, as well as significantly lower contents of starch, protein, and lipid compared to the wild type. The difference was exacerbated under high temperature conditions. Moreover, OsLEA1b was induced by drought stress. The survival rate of oslea1b mutants decreased significantly under drought stress treatment, with significant increase in ROS levels. These results indicate that OsLEA1b regulates starch biosynthesis and influences rice grain quality, especially under high temperatures. This provides a valuable resource for genetic improvement in rice grain quality. Full article