解析羧酸酯酶CXE15介导拟南芥株型发育的分子作用机制和信号途径

作为决定植物存活以及成功孕育后代的重要因素之一，植物的株型是由精确的遗传调控以及对外界环境的响应共同决定的，其调控机制是主要通过生长素和独脚金内酯（SLs）等激素信号通路协调腋芽的起始与伸长。深度挖掘实验室前期Microarray数据发现一个受生长素调控且地上地下组织表达相反的差异基因Carboxylesterase15/CXE15；进一步研究发现，CXE15过表达株系具有典型SLs信号缺陷突变体的多分枝表型，且对外源SLs处理不敏感。与SLs信号缺陷突变体类似，过表达株系中SLs合成途径相关基因表达显著上调，而抑制分枝的转录因子显著下调，暗示CXE可能作为介导SLs的一条新的信号通路影响植物分枝模式。本实验利用遗传学和分子生物学等方法，揭示CXEs与调控植物分枝的两种主要激素生长素和SLs之间的关系，阐明CXEs在调控植物株型的作用机制，建立一条CXEs介导的植物分枝发育调控的信号途径。

Plant architecture is one of the key factors contribute to plant survival and reproductivity. The branching pattern of plant is largely determined by genetic programs and external environmental cues such as light, nutrition, plant density, etc. Many of these cues are perceived locally, but require activation of systematical responses through a small number of signaling molecules, including Ca2+, ROS (Reactive Oxygen species), auxin, cytokinin, GA, etc. Of these molecules, the recent identified strigolactones (SL) has been found to play important roles in regulation of plant branching pattern via inhibition of axillary bud outgrowth. Based on the transcriptomic data re-analysis of our published CIM (Callus induced medium) experiment, a gene CXE15 (Carboxylesterase 15, belong to alpha/beta hydrolase superfamily) with opposite expression between shoot and root part was identified. Intriguingly, overexpression of CXE15 resulted in the SLs biosynthesis and signaling deficient mutants multi-branching phenotype, and genes involved in SLs biosynthesis is significantly upregulated in 35S:CXE15. Moreover, 35S:CXE15 exhibited SLs deficient mutant-liked insensitivity to SLs, on the contrary, salk mutant displayed more sensitive to SLs treatment, suggesting that CXE may function as a negative regulator of SLs signaling in modulation of plant branching. So far, no studies of CXE15 on plant branching development has been reported. Multiple tools and methodologies from genetics, biochemistry, bioinformatics and molecular biology will be adopted to investigate the role of CXEs in regulation of plant architecture possibly via hydrolysis of SLs or other indirection ways, and intend to fill some gaps in the signaling network of plant branching.