CsSUP调控黄瓜果实长度的分子机理研究

Cucumber (Cucumis stivus L.) is one of the most important fruit vegetables in China, and its commodity fruit is immature and tender. The fruit length directly affects the cucumber yield and commodity value. However, the key genes regulating fruit length and the corresponding molecular mechanisms are largely unknown. The cucumber SUPERMAN (CsSUP) gene encodes a C2H2 type zinc finger transcription factor. Our previous result showed that CsSUP is differentially expressed in the two near-isogenic lines with different fruit length；and knock-down of CsSUP in cucumber leads to short and small fruit. Ectopic expression of CsSUP in Arabidopsis results in reduced silique length. These data suggested that CsSUP is involved in fruit length control, but the specific molecular mechanism remains elusive. Thus, this project will utilize the methods and tools in molecular biology, biochemistry, developmental biology and vegetable physiology, to analyze the subcellular localization, response to hormones, cucumber transformation, gene regulating network, protein interactions, downstream targets of CsSUP, as well as its corresponding physiological index, so that uncover the physiological and biological function, and the molecular mechanism of CsSUP in fruit length regulation in cucumber. The results obtained in this project will provide the molecular markers and theory basis for molecular breeding for cucumber varieties with optimum fruit length, high yield and excellent quality.

黄瓜是我国最重要的果菜之一，其商品果为嫩果，果实的长短直接影响黄瓜的产量和商品价值，但果长调控的关键基因和分子机理知之甚少。黄瓜SUPERMAN（CsSUP）基因编码一个C2H2类型的锌指结构转录因子。我们研究发现，CsSUP在两份黄瓜果实长度不同的近等基因系材料中差异表达，干扰表达CsSUP基因导致黄瓜果实缩短变小；在拟南芥中异源表达CsSUP基因也导致果荚变短，表明CsSUP参与果实长度的调控，但其具体的分子作用机理尚不清晰。因此，本课题拟利用分子生物学、生物化学、发育生物学、以及蔬菜生理学等方法，从基因亚细胞定位、激素响应和调控、黄瓜遗传转化、基因调控网络、蛋白互作和下游靶基因的筛选和验证、相应生理指标分析等角度，深入研究CsSUP调控黄瓜果长的生理、生物学功能和分子作用机理，为培育长度适中、高产优质的黄瓜品种提供分子标记和理论依据。

黄瓜的果实长度因直接影响黄瓜产量与商品性而成为黄瓜驯化过程中一个关键选择性状，目前对于黄瓜果实长度调控机制的研究很少。前期我们通过对不同果长进行转录组测序，筛选得到了SUPERMAN基因在黄瓜的同源基因CsSUP, CsSUP在长果中有较高的表达量，干扰CsSUP的表达量导致果实长度变短。本项目我们发现另外一个调控果长的关键基因CsFUL1, CsFUL1属于MADS-box家族转录因子，且在短果中有高的表达量，一系列生化试验表明CsFUL1可以结合到CsSUP启动子区域调控其表达进而影响下游与细胞周期以及细胞膨大相关基因的表达来抑制果实伸长。通过对150份重测序材料进行分析发现在CsFUL1基因组序列3393位置存在一个SNP变化，即在华北型长果中表现为3393-A,其他类型黄瓜中均为3393-C。基因沉默CsFUL1A导致果实变长，过表达CsFUL1A导致果实变短，而改变CsFUL1C的表达量对果长没有任何影响，进一步说明CsFUL1A是在果长驯化过程中特异出现在华北型长果中的一个关键抑制因子。CsFUL1可以通过抑制CsPIN1和CsPIN7的表达进而影响生长素在果实中的运输来影响果长发育。因此我们的工作筛选并解析了一个涉及CsFUL1A, CsSUP和 CsPIN1/7的果长调控基因网络，为培育长度适中、高产优质的黄瓜品种提供分子标记和理论依据。