AGC1.5 Kinase Phosphorylates RopGEFs to Control Pollen Tube Growth
AGC1.5 Kinase Phosphorylates RopGEFs to Control Pollen Tube Growth
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AGC1.5 激酶磷酸化 RopGEF 以控制花粉管生长
DOI：
10.1016/j.molp.2018.07.004
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发表时间：
2018-09-10
期刊：
影响因子：
27.5
通讯作者：
Zhang, Yan
中科院分区：
文献类型：
--
作者：
Li, En;Cui, Yong;Zhang, Yan
被子植物的双受精需要将不动的精子通过花粉管定向地传递给卵子。植物顶端生长花粉管的极性是通过植物活性Rho gtp酶（ROP-GTP）与顶质膜的动态结合来维持的。鸟嘌呤核苷酸交换因子（RopGEFs）可催化ROP的活化，从而影响ROP的时空信号传导。虽然已经发现RopGEF是磷酸化蛋白，但在体内负责其磷酸化的激酶以及RopGEF磷酸化在花粉管生长中的生物学后果尚不清楚。我们在这里报道，拟南芥细胞质激酶AGC1.5亚家族对花粉管生长过程中ROP-GTP的限制性定位至关重要。AGC1.5和AGC1.7功能的缺失导致花粉管中活性ROP的错误定位和ROP信号下游的缺陷事件。AGC1.5与RopGEFs通过其催化的PRONE结构域相互作用，并在PRONE结构域的一个保守的Ser残基上磷酸化RopGEFs。AGC1.5和AGC1.7功能的缺失导致了RopGEFs在花粉管中的错误定位，类似于AGC1.5无法磷酸化RopGEFs的突变所导致的表型。总的来说，我们的研究结果为花粉管极性生长过程中ROPs的时空激活提供了机制见解。
Double fertilization in angiosperms requires the targeted delivery of immotile sperm to the eggs through pollen tubes. The polarity of tip-growing pollen tubes is maintained through dynamic association of active Rho GTPases of plants (ROP-GTP) with the apical plasma membrane. Guanine nucleotide exchange factors for ROPs (RopGEFs) catalyze the activation of ROPs and thereby affect spatiotemporal ROP signaling. Whereas RopGEFs have been found to be phosphorylated proteins, the kinases responsible for their phosphorylation in vivo and biological consequences of RopGEF phosphorylation in pollen tube growth remain unclear. We report here that the Arabidopsis AGC1.5 subfamily of cytoplasmic kinases is critical for the restricted localization of ROP-GTP during pollen tube growth. Loss of AGC1.5 and AGC1.7 functions resulted in the mistargeting of active ROPs and defective events downstream of ROP signaling in pollen tubes. AGC1.5 interacts with RopGEFs via their catalytic PRONE domain and phosphorylates RopGEFs at a conserved Ser residue of PRONE domain. Loss of AGC1.5 and AGC1.7 functions resulted in the mistargeting of RopGEFs in pollen tubes, similar to the phenotype caused by the mutation that renders RopGEFs non-phosphorylatable by AGC1.5. Collectively, our results provide mechanistic insights into the spatiotemporal activation of ROPs during the polar growth of pollen tubes.