RIP1 (ROP Interactive Partner 1)/ICR1 Marks Pollen Germination Sites and May Act in the ROP1 Pathway in the Control of Polarized Pollen Growth
RIP1 (ROP Interactive Partner 1)/ICR1 Marks Pollen Germination Sites and May Act in the ROP1 Pathway in the Control of Polarized Pollen Growth
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DOI：
10.1093/mp/ssn051
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发表时间：
2008-11-01
期刊：
影响因子：
27.5
通讯作者：
Yang, Zhen-Biao
中科院分区：
文献类型：
--
作者：
Li, Shundai;Gu, Ying;Yang, Zhen-Biao
Rho家族小GTP酶是真核细胞中控制细胞极性的通用信号开关。它们的极地分布到细胞皮质对于它们功能的执行是至关重要的，然而这种分布的机制却鲜为人知。利用酵母双杂交的方法，我们鉴定了RIP1(ROP Interactive Partner 1)，它属于一个新的蛋白家族，它具有与ROP相互作用的C-末端区域，在拟南芥花粉中表达时，绿色荧光蛋白GFP标记的RIP1定位于成熟花粉的细胞核。当花粉粒在萌发介质中水合时，GFP-RIP1在未来的花粉萌发部位从细胞核转移到细胞皮质，并维持在萌发花粉和生长花粉管的顶端皮质中。RIP1在花粉管中与ROP1相互作用，皮层RIP1的定位受ROP1活性的影响。RIP1的过表达诱导了花粉管的生长去极化，这种表型与ROP1过表达所诱导的表型相似。有趣的是，RIP1的过表达增加了GFP-ROP1在花粉管质膜(PM)上的募集。在这些观察的基础上，我们推测RIP1参与了ROP1定位到PM的正反馈调节，导致了花粉萌发和花粉管生长的极点的建立。
Rho family small GTPases are universal signaling switches in the control of cell polarity in eukaryotic cells. Their polar distribution to the cell cortex is critical for the execution of their functions, yet the mechanism for this distribution is poorly understood. Using a yeast two-hybrid method, we identified RIP1 (ROP interactive partner 1), which belongs to a family of five members of novel proteins that share a C-terminal region that interacts with ROP When expressed in Arabidopsis pollen, green fluorescence protein GFP-tagged RIP1 was localized to the nucleus of mature pollen. When pollen grains were hydrated in germination medium, GFP-RIP1 switched from the nucleus to the cell cortex at the future pollen germination site and was maintained in the apical cortex of germinating pollen and growing pollen tubes. RIP1 was found to interact with ROP1 in pollen tubes, and the cortical RIP1 localization was influenced by the activity of ROP1. Overexpression of RIP1 induced growth depolarization in pollen tubes, a phenotype similar to that induced by ROP1 overexpression. interestingly, RIP1 overexpression enhanced GFP-ROP1 recruitment to the plasma membrane (PM) of pollen tubes. Based on these observations, we hypothesize that RIP1 is involved in the positive feedback regulation of ROP1 localization to the PM, leading to the establishment of a polar site for pollen germination and pollen tube growth.