粒形是重要的产量性状和品质性状，阐明粒形遗传基础和分子机理有利于同时改良水稻的产量和品质。在已完成的基金委项目中，主要从基因表达调控水平解析水稻OsXCL基因功能，OsXCL正向调控水稻粒长、粒重，改良穗形、株形，改善米质。该基因可能通过CK信号传导途径正调控下游响应基因，促进细胞有丝分裂和轴向生长，调控水稻生长发育。进一步研究发现，该基因编码区包含一个未知功能结构域DUF1645，不同作物编码DUF1645的基因也能正调控水稻粒长、粒重，其完整性对粒长、粒重调控似乎是必须的。因数据库中无合适突变体，本项目拟在现有研究基础上，完成CRISPR/Cas9无义突变株表型及功能分析、酵母双杂交、BiFC、EMSA、OsXCL蛋白质特性分析，进一步阐明OsXCL可能的分子作用机制、DUF1645及其不同模块对粒形、粒重的调控功能，为高产、优质、“理想株型”超级稻分子选育提供新的候选基因和理论参考。

Grain size and shape are important determinants of grain yield and quality in cereal crops, which are usually controlled by non-allelic genes and quantitative trait loci (QTLs). OsXCL, encoding a nucleus-localized DUF1645 protein of unknown function. Overexpression of OsXCL greatly and positively affected an array of traits, including increases in grain length, grain weight and grain number per panicle, resulting in a significant increase in grain yield. In our previous study, the function and molecular analyses of OsXCL were investigated mainly at the transcriptional leve. The obtained data showed that the enhanced OsXCL expression in rice promoted cell division and grain filling. A large number of genes involved in plant cell cycle and cytokinin signaling processes were induced and suppressed in the OsXCL-overexpressing plants, suggesting that OsXCL may regulate cell growth by acting via a cytokinin signaling pathway. OsXCL encode a DUF1645 domain-containing protein.Three putative member of the DUF1645 protein familys are cloned from maize, sorghum and wheat. Similar to OsXCL, Overexpressions of the three OsXCL-like genes are significantly enhanced gain length and grain weight in transgenic rice plants. Further analysis showed that the intactness of DUF1645 domain seems critical for these genes to function in grain length and weight increases. The following experimental studies will be performed in this work: functional analysis of OsXCL by overexpressing and CRISPR/Cas9 gene knockout in transgenic rice lines, yeast two-hybrid, biomolecular fluorescence complementation analysis and EMSA analysis, spatial and temporal gene expression pattern assessment of expression of genes regulated by OsXCL. The main research objectives are to analyze the functions of the OsXCL related to grain size development, explore its mechanism of action, andrevealing the possible function and molecular mechanism of plant conserved DUF1645, and provide a theoretical reference and candidate gene to develop new high quality and yield rice varieties.