Characterization of a core module required for allocation decisions and adaptive responses in Arabidopsis.

自适应反应可以分为四个步骤：感知、信号整合、决策过程和这些决策的执行。虽然拟南芥领域在理解信号感知和整合方面取得了进展，但对决策过程(这里称为分配决定)及其执行知之甚少。为了解决这个问题，我们设立了一个“利益冲突”前瞻遗传筛查，以确定分配决策中的主要参与者。连同反向遗传方法和交互作用的筛选，我们已经发现了一个由三个组件组成的模块。该模块的第一个组件是毛发状激酶BIN2，它介导信号整合。第二个组成部分是保守的TRAPPII多亚基连接复合体，它介导了跨高尔基网络(TGN)的决策过程。第三个组分包括一系列Rab GTP酶，它们被定位为在前两个组分下游执行决策。为了剖析BIN2-TAPP-RAB模块信号会聚的分子机制，我们将结合蛋白质组学、生物化学、遗传学和高分辨率共聚焦显微镜。我们的具体目标是(1)阐明油菜素类固醇(BR)诱导的翻译后修饰对TGN相关的TRAPPII系留复合体的组装和功能的影响，(2)表征TAPP复合体和Rab GTP酶之间的功能相互作用，以及(3)评估这些修饰如何指导分拣和贩运决定。我们的研究将确定TGN信号调节分选决定的分子机制，这些决定有助于细胞分裂、伸长、生长各向异性和分生组织功能。在这里获得的机械性见解将为理解植物适应性生长和分配决策奠定基础。

Adaptive responses can be broken down into four steps: sensing, signal integration, decision making processes and the execution of these decisions. While progress has been made in the field of Arabidopsis to understand signal perception and integration, little is known about decision making processes (here referred to as allocation decisions) and their execution. To address this, we have set up a “conflict of interest” forward genetic screen to identify major players in allocation decisions. Together with reverse genetic approaches and screens for interactors, we have uncovered a three-component module. The first component of the module is the shaggy-like kinase BIN2, which mediates signal integration. The second component is the conserved TRAPPII multi-subunit tethering complex that mediates decision-making processes at the trans-Golgi-network (TGN). The third component comprises a family of Rab GTPases that are posited to execute decisions downstream of the first two components. To dissect the molecular mechanisms of signal convergence at the BIN2-TRAPP-RAB module, we will use a combination of proteomics, biochemistry, genetics and high-resolution confocal microscopy. Our specific goals are to (1) elucidate the impact of brassinosteroid (BR)-induced post-translational modifications on the assembly and function of the TGN-associated TRAPPII tethering complexes, (2) characterize functional interactions between TRAPP complexes and Rab GTPases, and (3) assess how these instruct sorting and trafficking decisions. Our study will identify molecular mechanisms by which signaling at the TGN modulates sorting decisions that contribute to cell division, elongation, growth anisotropy and meristem function. Mechanistic insights gained here will lay a foundation for understanding plant adaptive growth and allocation decisions.