黄瓜是世界性重要蔬菜作物，其器官大小不仅是发育生物学的重要问题，而且与株型结构、果实产量等农艺性状密切相关。黄瓜果实是研究器官大小的重要系统之一，然而果实发育的细胞学基础和调控网络非常复杂，参与细胞膨大过程的调控因子及其具体作用方式仍不清楚。申请人在前期研究中发现一个新的器官变小突变体“little organ（lo）”，该突变体叶片变小，果实不能膨大，果实组织切片结果表明该突变体细胞膨大过程受到严重影响。遗传规律分析表明该性状是由一个隐形单基因所控制，通过BSA-seq方法结合遗传连锁分析，将LO基因定位在160kb的物理区间。本项目拟在该工作基础之上，扩大群体对LO基因进行精细定位，并利用CRISPR/Cas9基因编辑等技术对其进行功能验证，进一步通过转录组分析以及生化手段探究LO基因调控果实早期发育的分子机制，为黄瓜的品种改良提供理论基础。

Cucumber is an important vegetable all over the world. The organ size is not only a developmental biological issue, but also closely associated with a series of agronomic traits such as plant architecture and fruit production. Fruit is one of the available systems to investigate organ size in cucumber. However, the cytological basis and regulatory network of fruit development are very complicated, little is known about genes and mechanism of cell expansion in fruit early development. In the previous study, we identified a new little organ cucumber mutant ‘little organ (lo)’ who has smaller leaves and smaller fruits that cannot expand, which was controlled by a single recessive gene named by ‘LO’. It was shown that cell expansion was severely affected in fruit development in mutant by cell section observation. By using BSA-seq and genetic linkage analysis, we delimited LO gene to a 160kb interval. Here, we will increase progeny population to complete the fine mapping of LO gene and identify its function through CRISPR/Cas9 genome editing technique. Furthermore, transcriptome analysis and biochemical assays will be used for revealing the role that LO plays in regulating fruit early development, and to some extent provide the theoretical basis for molecular breeding of cucumber.