不同类型的黄瓜品种对侧枝数量要求不同，解析黄瓜侧枝发育调控网络是选育不同侧枝类型品种的基础和前提，但由于侧枝数量相关基因的精细定位与克隆进展缓慢，迄今有关黄瓜侧枝发育的分子机制尚不清楚。申请人在青年基金的资助下，在黄瓜上通过QTL定位与图位克隆获得一个控制器官大小与侧枝数量的WD40转录因子LL。在黄瓜和拟南芥中将LL过表达会使侧枝数量显著减少，而在ll基因近等基因系中侧枝数量显著增加，但其调控侧枝发育的分子机制并不清楚。本项目拟在前期工作基础上，通过ChIP-seq技术筛选鉴定LL基因下游关键靶位点；通过酵母单杂交鉴定LL基因的上游调控因子；通过酵母双杂交文库筛选鉴定LL互作蛋白；同时对野生型和其ll基因近等基因系进行转录组和内源激素含量分析，最终揭示LL基因调控侧枝数量的网络途径与作用机理。预期研究结果不仅有助于丰富植物侧枝发育的调控机制，也可为黄瓜株型改良奠定理论基础。

Different cucumber types have different requirements for lateral branch number. Dissecting the developmental regulation network for lateral branch in cucumber is the basis and premise for breeding different varieties, while the lateral branch number is a quantitative trait and it is controlled by multiple genes, so it is difficult for fine QTL mapping and cloning of related genes which made the progress move slowly. To data, the regulation mechanism of the lateral branch development in cucumber is still unclear. We have cloned a gene LL (Little leaf) in cucumber by QTL mapping and positional cloning, which regulated organ size and lateral branch number. LL gene encodes a WD40 transcription factor. Overexpression of LL gene in cucumber and Arabidopsis significantly reduced the lateral branch number, while the lateral branch number was significantly increased in the ll gene near-isogenic lines. The molecular mechanism and regulation pathway for LL gene is still unknown. In the current project, we plan to identify the downstream target genes of LL using ChIP-seq analysis, and then identify the upstream regulators of LL gene by yeast one-hybrid library screening. Furthermore, the interacted proteins will be also identified by yeast two-hybrid library screening. The 9930 inbred line with its ll NIL line will also be used for comparison of the endogenous hormones level and transcriptome difference. Finally all the results will be integrated together to investigate the regulation network and the molecular mechanism of LL gene. The results will not only be helpful to enrich the regulation mechanism of plant lateral branch development, but also lay a theoretical foundation for improvement of cucumber plant architecture.