The Protein Phosphatases ATUNIS1 and ATUNIS2 Regulate Cell Wall Integrity in Tip-Growing Cells
The Protein Phosphatases ATUNIS1 and ATUNIS2 Regulate Cell Wall Integrity in Tip-Growing Cells
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DOI：
10.1105/tpc.18.00284
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发表时间：
2018-08-01
期刊：
影响因子：
11.6
通讯作者：
Boisson-Dernier, Aurelien
中科院分区：
文献类型：
--
作者：
Franck, Christina Maria;Westermann, Jens;Boisson-Dernier, Aurelien
快速生长的植物细胞，如花粉管(PTS)和根毛(RHS)，需要在其内部生长机制和其细胞外坚硬但可伸展的细胞壁(CW)的修改之间进行强有力的协调。这种重要的协调作用部分由长春花类受体样激酶1(CrRLK1L)亚家族成员控制，其中FER及其最接近的同源物ANXUR1(ANX1)和ANX2分别控制着RH和PT生长过程中CW的完整性。最近，富亮氨酸重复序列Extensin 8(LRX8)到LRX11也被证明对PTS的CW完整性很重要。我们之前在拟南芥中报道了一个ANX1-ANX2抑制子的筛选，它揭示了Maris(MRI)是FER和ANX1/2依赖的CW完整性通路的正调控因子。在这里，我们描述了一个抑制子，它表现出对ANX1 ANX2 PT爆发表型和短RH表型的弱挽救。相应的抑制子突变导致一种类型的蛋白磷酸酶D94N替换，我们称之为ATUNIS1(AUN1)。我们发现AUN1及其最接近的同源基因AUN2是尖端生长的核质负调控因子。此外，我们还证明了AUN1(D94N)和AUN1(H127A)在保守的磷酸蛋白磷酸酶催化部位的关键氨基酸突变是抑制PT生长的显性非晶变异体。最后，使用超晶型MRIR240C和无晶型AUN1(D94N)显性变异体的遗传交互作用研究表明，LRX8-11和ANX1/2在顶端生长过程中以不同但收敛的途径微调CW完整性。
Fast tip-growing plant cells such as pollen tubes (PTs) and root hairs (RHs) require a robust coordination between their internal growth machinery and modifications of their extracellular rigid, yet extensible, cell wall (CW). Part of this essential coordination is governed by members of the Catharanthus roseus receptor-like kinase1-like (CrRLK1L) subfamily of RLKs with FERONIA (FER) and its closest homologs, ANXUR1 (ANX1) and ANX2, controlling CW integrity during RH and PT growth, respectively. Recently, Leucine-Rich Repeat Extensin 8 (LRX8) to LRX11 were also shown to be important for CW integrity in PTs. We previously reported an anx1 anx2 suppressor screen in Arabidopsis thaliana that revealed MARIS (MRI) as a positive regulator of both FER- and ANX1/2-dependent CW integrity pathways. Here, we characterize a suppressor that exhibits a weak rescue of the anx1 anx2 PT bursting phenotype and a short RH phenotype. The corresponding suppressor mutation causes a D94N substitution in a Type One Protein Phosphatase we named ATUNIS1 (AUN1). We show that AUN1 and its closest homolog, AUN2, are nucleocytoplasmic negative regulators of tip growth. Moreover, we demonstrate that AUN1(D94N) and AUN1(H127A) harboring mutations in key amino acids of the conserved catalytic site of phosphoprotein phosphatases function as dominant amorphic variants that repress PT growth. Finally, genetic interaction studies using the hypermorph MRIR240C and amorph AUN1(D94N) dominant variants indicate that LRX8-11 and ANX1/2 function in distinct but converging pathways to fine-tune CW integrity during tip growth.