动物RhoGTP结合蛋白及其植物对应物,植物Rho(ROP),调节细胞极性,但是它们是通过不同的效应蛋白来实现的。一类ROP效应器,组成型活性ROP(ICR)/ROP交互伙伴(RIP)的相互作用者,已经牵涉到不同的生物过程;然而,对RIP功能丧失突变体的分析有限。这里,我们报告了拟南芥RIP在叶表皮中的功能分析。所有RIP共定位于皮质微管的绿色荧光蛋白(GFP)融合蛋白。RIP1,RIP3和RIP4,而不是RIP2和RIP5,与前相带(PPB)共定位,纺锤体和植体。RIP2和RIP5不与PPB共定位,纺锤体或原生质体,即使它们在增殖细胞中活跃的启动子下表达,表明RIP蛋白性质之间存在差异。RIP1或RIP4的过表达导致皮质微管断裂,与野生型相比,rip12345五重突变体的正端微管生长速率增加。rip12345突变体叶片和花瓣狭窄,这可以解释为与野生型相比,沿横轴的细胞数量减少。与野生型相比,rip12345突变体叶表皮具有较少朝向叶片长轴的PPB,表明RIPs参与细胞分裂平面调节和叶片形状测定。
Animal Rho GTP-binding proteins and their plant counterparts, Rho of plants (ROPs), regulate cell polarity, but they do so through different effector proteins. A class of ROP effectors, interactor of constitutive active ROPs (ICRs)/ROP interactive partners (RIPs), has been implicated in diverse biological processes; however, there are limited analyses of RIP loss-of-function mutants. Here, we report an analysis of the functions of the Arabidopsis thaliana RIPs in the leaf epidermis. Green Fluorescent Protein (GFP) fusion proteins of all the RIPs colocalized to cortical microtubules. RIP1, RIP3 and RIP4, but not RIP2 and RIP5, colocalized with the preprophase band (PPB), spindles and phragmoplasts. RIP2 and RIP5 did not colocalize with the PPB, spindles or phragmoplasts even when they were expressed under a promoter active in proliferative cells, indicating that there are differences among RIP protein properties. The overexpression of RIP1 or RIP4 resulted in the fragmentation of cortical microtubules, and the rip1 2 3 4 5 quintuple mutant showed increased growth rate of microtubules at their plus ends compared with the wild type. The rip1 2 3 4 5 mutant leaves and petals were narrow, which was explained by the decreased cell number along the transverse axis compared with that of the wild type. The rip1 2 3 4 5 mutant leaf epidermis possessed fewer PPBs oriented close to the long axis of the leaf compared with wild type, indicating the involvement of RIPs in cell division plane regulation and leaf shape determination.