微管结合蛋白WDL4调控囊泡运输参与顶端弯钩细胞生长的分子机理

The specific protein transport and localization mediated by cytoskeleton-vesicular trafficking system is crucial for cell growth. In plants, the formation and regulation of the apical hook, which is essential for the successful penetration through the soil and survival of the seedlings, requires the asymmetric auxin distribution across the hypocotyl. The establishment of asymmetric auxin distribution largely relies on polar auxin transport mediating carriers, which are regulated by vesicular trafficking system. However, the function of microtubule cytoskeleton and microtubule associated proteins (MAPs) in these processes is largely unknown. In the preliminary study, we have identified a new MAP WDL4 which is involved in the opening of apical hook and affects auxin distribution. What is more, WDL4 interacts with the SNARE protein SYP121. Based on these results, we propose to investigate the function of WDL4 in the physiological process of apical hook opening, and to unravel the molecular mechanism of WDL4 regulating the vesicular trafficking through its interaction with SYP121, thus affecting asymmetric auxin distribution and cell growth in the apical hook. These studies will greatly improve our understanding on the regulation mechanisms of differential cell growth in the apical hook. Especially, it will provide new information to the physiological function of microtubule and MAPs in asymmetric cell growth in plants.

细胞骨架-囊泡系统所介导的蛋白质运输和特异性定位与植物细胞的生长调控密切相关。下胚轴顶端弯钩 (apical hook)结构的形成和调节对于植物幼苗出土和存活至关重要，其中生长素在弯钩两侧的不对称性分布对该结构的形成和维持是必需的。生长素分布依赖于囊泡运输过程介导的生长素转运蛋白极性定位，然而微管骨架在其中的功能及调控机制并不清楚。申请人在前期研究中发现拟南芥微管结合蛋白WDL4参与了顶端弯钩打开的生理学过程，并影响了生长素的分布，而且WDL4与SNARE蛋白SYP121相互作用。在此基础上，申请人拟深入研究WDL4参与调控幼苗顶端弯钩打开的具体机制，阐明WDL4-SYP121相互作用通过微管骨架-囊泡系统调控生长素分布进而介导弯钩两侧细胞差异性生长的分子机制。本项研究对于解析植物下胚轴顶端弯钩细胞生长的调控机理，特别是阐明细胞骨架在植物细胞差异性生长中的功能和作用机制有着重要的意义。

下胚轴顶端弯钩结构的形成和调节对于植物幼苗出土和存活至关重要。激素乙烯是弯钩形成的关键调节因子，而弯钩内外两侧生长素的不对称性分布对两侧细胞的差异性生长是必需的。微管骨架在维持植物细胞形态和调控细胞生长等方面起着关键的作用，其功能受到多种微管结合蛋白的调控。然而，微管骨架和微管结合蛋白是否参与顶端弯钩细胞生长并不清楚。本项目围绕在顶端弯钩发育过程中乙烯、微管结合蛋白与生长素分布之间的功能关系和调控机制来展开。研究发现，微管结合蛋白WDL4是顶端弯钩张开的正调控因子，其在顶端弯钩的基因表达模式受乙烯信号通路中关键转录因子EIN3的负调控。WDL4影响顶端弯钩生长素的不对称分布和生长素外向转运蛋白的运输。而且，WDL4可以与SNARE蛋白SYP121相互作用，可能通过促进SNARE复合体的形成，参与囊泡运输过程。综上所述，本研究阐明了微管结合蛋白WDL4促进顶端弯钩打开的功能和具体机制，有助于我们进一步理解顶端弯钩细胞生长的调控机理，为揭示微管结合蛋白介导植物细胞差异性生长的细胞学机制提供了新的理论依据。