Abstract:

【Objective】Small and round grain mutants serve as ideal genetic materials for dissecting the regulation mechanism of rice grain size and can provide new breeding material for yield improvement.【Method】BSA-Seq was employed to delimit the causal locus in the small and round grain mutant srg10. Candidate gene was functionally verified by CRISPR/Cas9-mediated knockout. The phenotypic effects of srg10 on the main yield-related traits were identified, and the underlying mechanism modulating grain size was investigated.【Result】The srg10 mutation significantly reduced grain number per panicle and grain weight, resulting in a pronounced yield penalty. A single nucleotide substitution (SNP, G>A) within the Os10g0363700 gene was identified as the cause for the small and round grain phenotype. Comparative transcriptome profiling of young panicles from srg10 and wild-type plants revealed 292 differentially expressed genes (DEGs). GO enrichment analysis showed that these DEGs are predominantly associated with biological processes such as cell development, cell growth, and signal transduction. Expression profiling of known grain size genes further suggested that the srg10 mutation may involve multiple regulatory pathways such as cell cycle, transcriptional regulation, RNA splicing, and plant hormones, thereby modulating panicle development.【Conclusion】Mutation of Os10g0363700 produces pleiotropic, yield-adverse phenotypes characterized by small and round grains. RNA-Seq analysis showed that the mutant gene may be related to cell microfilament organization, and may also directly or indirectly regulate grain size via known grain size genes.

Key words: rice, grain size, BSA-Seq, small and round grain, SRG10

摘要：

【目的】短圆粒突变体是研究水稻粒形调控机制的理想材料，可为水稻产量育种提供新的靶标和育种材料。【方法】利用BSA-Seq技术对水稻短圆粒突变体srg10的突变基因进行了定位，并利用CRISPR/Cas9敲除技术对候选基因进行了功能验证，鉴定了srg10对水稻主要产量性状的效应，并分析了其影响粒形的机制。【结果】突变体srg10每穗粒数、粒重等主要农艺性状均受到显著影响，产量有明显降低趋势，同时蒸煮食味品质等也受到影响。Os10g0363700基因上的一个单核苷酸多态性(single nucleotide polymorphism, SNP)，即由G突变为A是srg10产生短圆粒表型的原因。突变体srg10幼穗中出现292个差异表达基因，GO富集分析显示，这些差异表达基因主要与细胞发育生长、信号响应等生物学过程相关。已知粒形基因表达分析显示srg10突变可能涉及细胞周期、转录因子、RNA剪接、植物激素等调控通路，实现对幼穗发育的调控。【结论】Os10g0363700基因突变会产生短圆粒等不利产量的表型，RNA-Seq分析表明该突变基因可能与细胞微丝形成有关，同时也可能通过已知粒形基因直接或间接作用调控粒形。

关键词: 水稻, 粒形, BSA-Seq, 短圆粒突变体, SRG10