Regulation of ROP signaling in cell division and cell expansion by a small ROPGAP family

细胞极性的建立，即细胞内容物的不均匀分布，是细胞形态发生的先决条件。细胞极性在细胞、组织和器官水平上受遗传控制和协调，以确保植物功能器官的定型繁殖。进化保守的植物Rho （ROP）小细胞质gtpase家族在细胞极性信号传导中起着分子开关作用，并协调细胞内容物的时空分布。调节蛋白使小rho - gtpase的活性和不活性之间切换。鸟嘌呤核苷酸交换因子（RopGEF）可以代替鸟嘌呤二磷酸（GDP）代替鸟嘌呤三磷酸（GTP）促进鸟嘌呤二磷酸的活化。相反，GTP酶激活蛋白（RopGAP）加速了GTP本质上缓慢的水解，并使相应的靶ROPs失去活性。对rop失活的调控知之甚少。我们之前关于RopGAPs亚家族的PHGAP对ROP失活的研究表明，它们与细胞分裂有关。它们定位于质膜和分裂位点，并需要运动蛋白激酶-12 POK在该位点保留。我们假设phgap在特定rop的失活中起作用，以建立分裂位点/肌动蛋白耗尽区，以确保正常的细胞分裂。我们将进一步了解phgap在细胞分裂过程中的调控和细胞动力学。我们将阐明哪些rop被PHGAP灭活，我们将确定新的相互作用伙伴，以研究PHGAP蛋白功能是如何被调节的。此外，我们将建立瞬时重构分析来重建rop信号模块，并研究它们的时空调节。

The establishment of cell polarity, an unequal distribution of cellular content, is a prerequisite of cellular morphogenesis. Cell polarity is under genetic control and coordinated at the cell-, tissue- and organ- level, to ensure the stereotypic reproduction of functional plant organs. The evolutionary conserved family of Rho of plant (ROP) small cytosolic GTPases serves as molecular switches in cell polarity signaling and orchestrate the spatio-temporal distribution of cellular content. Regulatory proteins enable the switching between activity and inactivity of the small Rho-GTPases. The Guanine nucleotide exchange factors (RopGEF), replace guanosin diphosphate (GDP) for guanosine triphosphate (GTP) to promote ROP activation. On the contrary, GTPase activating proteins (RopGAP) accelerate the intrinsically slow hydrolysis of GTP and render the respective target ROPs inactive. Little is known about the regulation of ROP-inactivation. Our previous work on ROP inactivation by the PHGAP subfamily of RopGAPs, implicated them in cell division. They localize to the plasma membrane and the division site and require the motor-protein kinesin-12 POK for retention at that site. We hypothesis that PHGAPs act in the inactivation of specific ROPs to set up the division site/actin depleted zone to ensure normal cell division. We will gain further insights into the regulation and cellular dynamic of PHGAPs during cell division. We will clarify which ROPs are inactivated by PHGAPs and we will identify novel interaction partners to investigate how PHGAP protein function is regulated. In addition we will establish transient reconstitution assays to recreate ROP-signaling modules and investigate their spatio-temporal regulation.