橡胶树乳管代谢调控转录因子的深度发掘与功能分析

Latex regeneration, the main metabolism occuring in laticifers of Hevea brasiliensis (para rubber tree), is a kind of secondary metabolism that responds to to the tapping stress, as well as a rate-limiting step for latex production. Transcriptional regulation plays a principal role in plant stress response and secondary metabolism. Hitherto, it remains unclear how the transcription factors (TF) are involved in regulating latex regeneratin. In this project, we will extensively screen the TFs and their candidate target genes in laticifers, and identify the key TFs and their target genes involved in latex regeneration. We will investigate the correlation between latex yield and TF-target gene coexpression as well as metabolic analysis, using the Hevea varieties with differing yielding and the ethylene-stimulation technique. The specific TF-target gene relationship will be determined by the analyses of qRT-PCR，yeast one hybrid and transgenic technology. Our ultimate target is to unravel the major TF-involved gene expression regulatory network in laticifers. The results of this project will help understand the molecular mechanisms underlying TF-involved latex regeneration in laticifiers, enrich the theory of rubber production, and provide theoretical guidance to yield-oriented genetic improvement in Hevea.

胶乳再生是橡胶树产胶细胞（乳管）的主要代谢活动，是橡胶树应答割胶胁迫的一种次生代谢，同时是橡胶产量形成的决定环节。转录调控在植物的胁迫应答、次生代谢中起着重要作用，而目前并不清楚乳管内的转录因子是如何介导胶乳再生调控的。本项目将在全基因组水平上系统鉴定乳管内表达的转录因子及其候选靶基因，利用不同产胶水平橡胶树品种和产量调控手段（乙烯刺激），分析候选转录因子及其靶基因的共表达与胶乳产量形成的相关性，结合相关胶乳代谢物测定，筛选鉴定控制胶乳再生的关键转录因子及其调控的功能基因，并通过酵母单杂、荧光定量PCR以及转基因等技术，验证转录因子与启动子的结合和转录激活活性，最终构建调控乳管代谢的主要转录因子调控网络。项目结果，有助于揭示乳管中转录因子参与胶乳再生调控的分子机制，充实和完善橡胶生物合成的调控理论，为橡胶树高产定向遗传改良提供理论指导。

胶乳再生是橡胶树乳管的主要次生代谢活动，而乳管内转录因子是如何调控这一次生代谢过程并不清楚。本项目从橡胶树全基因组鉴定了57个转录因子家族的2554个成员，通过不同组织的转录表达分析鉴定到乳管特异或显著高表达转录因子99个，其中12个基因是排他性的在胶乳中表达。分别进行乙烯处理实验、割胶处理实验、不同产量水平品种实验，结合胶乳生理参数及代谢组测定，筛选到胶乳再生相关转录因子277个，并进行预测靶基因。最后利用1316个基因和3204个基因对构建了胶乳再生中的转录调控网络。综合利用荧光定量、酵母单杂等分子生物学手段对橡胶树转录因子HbBES1及HbERF进行系统分析和深入研究，证明HbBES1与HbTAF12B、HbTIF3C1和HbDnaJ互作参与割胶和乙烯刺激应答，HbERF特别是HbERF-IXc4在乙烯利处理下对胶乳HbSUT3表达激活起关键作用，促进胶乳再生。本项目的完成，证实了转录因子在胶乳再生中的调控作用，充实和完善了橡胶生物合成的调控理论，为橡胶树高产定向遗传改良提供理论指导。