A positive feedback circuit for ROP-mediated polar growth
A positive feedback circuit for ROP-mediated polar growth
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ROP 介导的极性生长的正反馈电路
DOI：
10.1016/j.molp.2020.11.017
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发表时间：
2021-03-01
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;Zhang, Yu-Ling;Zhang, Yan
尖端生长是一种特殊类型的极化生长，在这种生长中，一个单一的、独特的极化位点被建立和维持。植物Rho蛋白（Rho of Plants， ROP）是植物中唯一一类Rho gtpase，其作用是调控茎尖的生长。rop的动态和非对称分布对于叶尖生长的建立和维持至关重要，并且至少需要一个正反馈回路，这仍然是难以捉摸的。在这里，我们报道了一个对根毛生长至关重要的正反馈回路，其中ROP、ROP激活物和效应物以及AGC1.5亚家族激酶通过顺序寡聚化和磷酸化相互连接。AGC1.5亚家族激酶与ROPs中的两个鸟嘌呤核苷酸交换因子RopGEF4和RopGEF10相互作用并使其磷酸化。它们还与两个ROP效应物ICR2/RIP3和mid1 /RIP4相互作用，它们将活性ROP与AGC1.5连接起来。AGC1.5亚家族激酶或ICR2和mid1的功能丧失由于ROP信号的减少而损害了根毛生长。我们发现RopGEF4和RopGEF10的不对称靶向是由agc1.5依赖性磷酸化控制的。有趣的是，我们发现在根毛生长过程中，ROP效应物将AGC1.5招募到质膜上活跃的ROP结构域，并且对于AGC1.5依赖性ropgef的磷酸化至关重要。考虑到植物中大量的AGC激酶，这种正反馈回路可能是植物细胞极性生长的普遍主题。
Tip growth is a special type of polarized growth in which a single and unique polarization site is established and maintained. Rho of Plants (ROP) proteins, which represent the only class of Rho GTPases in plants, regulate tip growth. The dynamic and asymmetric distribution of ROPs is critical for the establishment and maintenance of tip growth, and requires at least one positive feedback loop, which is still elusive. Here, we report a positive feedback circuit essential for tip growth of root hairs, in which ROPs, ROP activators and effectors, and AGC1.5 subfamily kinases are interconnected by sequential oligomerization and phosphorylation. AGC1.5 subfamily kinases interact with and phosphorylate two guanine nucleotide exchange factors (GEFs) of ROPs, RopGEF4 and RopGEF10. They also interact with two ROP effectors, ICR2/RIP3 and MIDD1/RIP4, which bridge active ROPs with AGC1.5. Functional loss of the AGC1.5 subfamily kinases or ICR2 and MIDD1 compromised root hair growth due to reduced ROP signaling. We found that asymmetric targeting of RopGEF4 and RopGEF10 is controlled by AGC1.5-dependent phosphorylation. Interestingly, we discovered that the ROP effectors recruit AGC1.5 to active ROP domains at the plasma membrane during root hair growth and are critical for AGC1.5-dependent phosphorylation of RopGEFs. Given the large number of AGC kinases in plants, this positive feedback circuit may be a universal theme for plant cell polar growth.