Search Results (105)

The non-specific lipid transfer proteins (nsLTPs) are able to bind various hydrophobic compounds and facilitate the transport of fatty acids between intracellular membranes, and nsLTPs are found in rice endosperm and embryo during seed development. However, whether nsLTPs function as lipid carriers and thereby affect lipid metabolism in rice grains remains unclear. To elucidate whether nsLTPs influence fatty acid distribution in rice, we generated OsLTP10-OE (OsLTP10 overexpression) and OsLTP10-CR (OsLTP10 CRISPR/Cas9) lines. Phenotypic and metabolic analyses indicated that OsLTP10 expression is closely associated with fatty acid (FA) profiles and grain appearance. In general, total fatty acid content in the brown rice of OsLTP10-OE was higher than that in wildtype, but OsLTP10-CR was lower than wildtype. While FA accumulation was altered in both tissues, the endosperm (milled grain) was more severely affected than the bran, with individual FAs in the milled grains of OsLTP10-OE expanding by 31.87–52.00%. Additionally, key grain quality traits were substantially altered; OsLTP10-CR lines displayed a significantly enlarged white-belly chalkiness area alongside a 19.50% reduction in amylose content, whereas OsLTP10-OE lines showed decreased chalkiness and a 7.80% increase in amylose. Overall, the fatty acid content and composition, chalkiness, brown rice size, and amylose were influenced by OsLTP10. Full article

Chalkiness is a complex quantitative trait regulated by both genetic and environmental factors. Reducing chalkiness has long been a research focus in rice genetics and breeding. A total of 108 markers on/closely linked to starch biosynthesizing genes, grain shape and chalkiness QTLs were used to detect interactions affecting chalkiness. A total of 30 and 39 marker pairs with significant bigenic epistasis were identified for percentage of grain with chalkiness (PGWC) and degree of endosperm chalkiness (DEC), respectively, of which 16 were commonly found in both traits. Using markers associated with chalkiness and marker pairs with significant epistatic effects as candidate predictors increased the coefficient of determination (R²) of the best multiple regression models for predicting both traits. GBSSI, SSIIa and the interaction between GBSSI and GBSSII were consistently identified in optimal models, indicating their critical roles in regulating rice chalkiness. R² for DEC and PGWC ranged from 36.5% to 42.7% and from 52.9% to 73.8% in two environments, respectively. PGWC decreased significantly from 38.9% to 15.10% after three cycles using marker-assisted recurrent selection (MARS). This study suggests that epistasis contributes substantially to the regulation of chalkiness, and demonstrates that MARS can effectively improve chalkiness without imposing obvious negative impacts on eating quality. Full article

Temperature and nitrogen fertilizer are key environmental factors that significantly affect rice growth and grain quality. There remains a lack of systematic research on the effects of temperature and nitrogen fertilizer on carbon–nitrogen metabolism during grain-filling, and consequently on the taste quality of rice varieties with different taste characteristics. To bridge this gap, pot experiments were conducted under different temperature and nitrogen fertilizer conditions to investigate the changes in carbon and nitrogen metabolism and the quality of different high-quality and stable-taste rice varieties during the grain filling stage. Our research results indicate that high-temperature conditions inhibit both carbon and nitrogen metabolism; however, the variations differ among rice varieties with differing taste stability. Under both normal and high nitrogen levels, compared to Akita Komachi (AK), a variety with poor taste stability, Jikedao 606 (J 606), a variety with strong taste stability, maintained a certain photosynthetic capacity under high-temperature conditions, with smaller decreases in net photosynthetic rate and soil–plant analysis development values, declining by 4.30–5.59% and 4.30–5.59% respectively. The decline in the activities of nitrate reductase, glutamine synthetase, and glutamate synthase in nitrogen metabolism was relatively small; in comparison, the decrease in the activities of ADP-glucose pyrophosphorylase, granule-bound starch synthase, starch branching enzyme, and starch debranching enzyme in carbon metabolism was comparatively minor. The content of amylose and amylopectin in the grains was maintained, improving the milled rice rate and head rice rate, thereby ensuring strong stability of excellent sensory quality. Under both high-temperature and high-nitrogen conditions, the yields of the two rice varieties were maintained. In summary, variations exist in carbon and nitrogen metabolism among different rice varieties with stable excellent taste under varying temperature and nitrogen fertilizer conditions. These metabolic differences affect starch synthesis in the endosperm, ultimately influencing the stability of rice sensory quality. This study provides a theoretical basis for nitrogen fertilizer application under high-temperature conditions and the cultivation of rice varieties with excellent taste stability. Full article

Background/Objectives: FLOURY ENDOSPERM 2 (FLO2) is known to affect rice endosperm development and starch quality, yet its role in determining flour physicochemical behavior and endosperm structural integrity has not been quantitatively defined. This study aimed to elucidate how loss of FLO2 function alters starch organization and functional properties of rice flour. Methods: Two independent homozygous, T-DNA-free OsFLO2 knockout lines were generated in the japonica cultivar Dongjin using CRISPR/Cas9. Grain appearance was evaluated in mature seeds. Flour physicochemical properties were analyzed by Rapid Visco Analyzer (RVA) and differential scanning calorimetry (DSC). Amylopectin chain-length distribution was determined by isoamylase debranching followed by HPAEC-PAD, and endosperm microstructure was examined by scanning electron microscopy. Results: OsFLO2 mutants exhibited floury, opaque endosperms, with chalkiness increasing from 4.8% in the WT to 27–29%. RVA analysis showed a marked reduction in peak viscosity (1193 cP to 263–293 cP) and a decrease in pasting temperature (77.2 °C to 68.9–70.5 °C). DSC indicated a tendency toward reduced gelatinization enthalpy in the mutants. These changes were associated with a reduced proportion of short amylopectin chains (DP 6–12), decreased long chains (DP ≥ 37), and a relative increase in intermediate-long chains (DP 25–36), along with disrupted granule packing and a 1.33–1.36-fold increase in endosperm porosity. Conclusions: These results demonstrate that FLO2 plays an important role in maintaining the structural integrity of rice endosperm by harmonizing the microstructure of amylopectin with the thermal and gelatinization properties of starch. Full article

Water scarcity is a major constraint to upland rice production, and optimizing drought management to balance yield and quality is critical for sustainable agriculture. This study investigated the effects of three soil water potential (SWP) levels—0 kPa (control), −20 kPa (moderate drought), and −40 kPa (severe drought)—on grain quality, nitrogen metabolism, and endosperm structure in two upland rice varieties (Brazilian upland rice and Zhonghan 3). Compared with the control, moderate drought significantly improved grain quality: whole milled rice recovery increased by 5.3–7.8%, chalky grain rate decreased by 16.1–29.6%, amylose content declined by 8.65–12.19%, and glutelin content rose by 9.3–12.9%. Under moderate drought, nitrogen metabolism appeared to be upregulated, as indicated by increased activities of glutamine synthetase (GS, +18.6%) and glutamate dehydrogenase (GDH, +14.2%) and higher glutamate content (+21.4%) in Zhonghan 3, with similar but slightly attenuated responses in Brazilian upland rice. Moderate drought was associated with elevated glutelin accumulation and a more compact endosperm microstructure, suggesting a potential link between nitrogen metabolism and grain development. In contrast, severe drought impaired both grain quality and yield. Correlation analysis (n = 12) revealed that the GS/GDH ratio and glutelin content were significantly correlated with improved grain quality—positively with milled rice recovery (r = 0.58 * to 0.82 **, p < 0.05 or 0.01) and negatively with chalkiness, amylose content, and setback viscosity (r = −0.58 * to −0.93 **, p < 0.05 or 0.01). These findings indicate that maintaining SWP at −20 kPa represents a feasible strategy to enhance upland rice grain quality, offering a theoretical basis for water-saving, quality-oriented production systems. Full article

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

Ensuring food security is a challenge for humans. Rice grain yield and quality must urgently be increased to overcome this challenge. MicroRNA (miRNA) is an important regulatory module in plant development and stress responses. Grain yield and quality are pleiotropic traits that employ cooperative genetic factors, including miRNA and its regulatory mechanisms. This review provides an overview of plant miRNAs and the composition and development process of rice grains. It also summarizes the research progress in miRNA regulation for agronomically important rice grain traits, providing a basis for further identifying miRNAs related to rice grain development and elucidating their regulatory mechanisms. 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

Seed development plays a critical role in determining both crop yield and grain quality in rice. As a key nutrient storage organ, the rice endosperm development not only contributes to grain filling but also plays an essential role during the early stages of seed germination. Amino acid metabolism is active during the process of seed development and seed germination. Asparagine is a primary amino acid responsible for long-distance organic nitrogen transport in plants. Asparagine synthetase catalyzes the synthesis of asparagine from aspartate and glutamine. In this study, CRISPR/Cas9-mediated knockout mutants of the OsASN2 gene of rice were generated. Homozygous mutants exhibited complete failure of seed germination, and heterozygotes could not produce homozygous offspring. Endosperm development of homozygous mutant seeds showed severe defects. Additionally, interacting protein screening combined with pull-down and co-immunoprecipitation (Co-IP) assays confirmed that OsASN2 physically interacted with pyruvate phosphate dikinase OsPPDKB, the mutants of which showed impaired endosperm development. These findings collectively indicate that OsASN2 plays a critical role in seed development and germination in rice. Full article