转录因子LcBZR1/2介导BR调控荔枝幼果脱落的机制研究

生理落果严重是荔枝产量低而不稳的重要原因。项目组前期研究证实乙烯是诱导荔枝幼果脱落的主因，近期又惊喜的发现油菜素内酯(BR)显著降低果实中乙烯释放，进而减少幼果脱落，但BR参与调控植物器官脱落的分子机制在模式植物和栽培作物中都未见报道。本项目前期研究表明，异源表达荔枝BR信号转导途径转录因子BZR(LcBZR1和LcBZR2)显著推迟器官脱落。因此，本项目拟重点以LcBZR1/2为切入点，探究BR调控荔枝落果的分子机制。首先利用VIGS证实LcBZR1/2调控荔枝幼果脱落的功能；同时对其原位表达、亚细胞定位及转录活性进行分析以揭示其分子特性；其次通过DAP-Seq、EMSA和酵母cDNA文库筛选获得LcBZR1/2调控落果相关靶基因及互作蛋白；最后利用VIGS对互作蛋白和靶基因进行功能验证。项目前期基础扎实，可行性强，研究结果将为荔枝落果调控提供理论支撑，也将拓展对器官脱落调控网络的认知。

Heavy physiologic fruit abscission has become a limiting factor for the litchi industry development. The induction of ethylene has been found to be the main factor for activating the fruitlet abscission in litchi. Interestingly, the induction of ethylene prior to abscission can be greatly repressed by brassinosteroid (BR) application, resulting in reduced fruit abscission rate. Though it is well known that BR plays a critical role in plant growth and development, the molecular mechanism underlying the regulation of plant organ abscission by BR is poorly understood in both model plants and cultivated crops. Thus, based on the findings that ectopic expression of two litchi BZR transcription factors (LcBZR1 and LcBZR2) in Arabidopsis significantly delayed the floral organ abscission process, we plant to explore the mechanism of BR mediated by LcBZR1/2 in regulating the fruitlet abscission in litchi. First, assays of virus-induced gene silencing (VIGS) and ectopic gene transformation will be performed to confirm the functions of LcBZR1/2 in control of organ abscission in lithci, meanwhile, assays of in situ hybridization, subceullar localization, and transcription activity will be used to test the molecular characterization of LcBZR1/2; next, to screen the target genes of LcBZR1/2 via DNA affinity purification sequencing (DAP-seq) and electrophoretic mobility shift assay (EMSA) aaaays, followed by screening the interaction proteins of LcBZR1/2 that involved in the litchi fruit abscission by screening a yeast cDNA library; finally, assays of VIGS will be performed to examine the functions of these target genes and interaction proteins in control of organ abscission. The results obtained in this project will not only expand the mechanism controlling plant organ abscission, but also provide new essential theoretical support for improving the cultivation management and cultivars of litchi.