Protein phosphatase 2A promotes stomatal development by stabilizing SPEECHLESS in Arabidopsis
Protein phosphatase 2A promotes stomatal development by stabilizing SPEECHLESS in Arabidopsis
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DOI：
10.1073/pnas.1912075117
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发表时间：
2020-06-09
影响因子：
11.1
通讯作者：
Dong, Juan
中科院分区：
文献类型：
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作者：
Bian, Chao;Guo, Xiaoyu;Dong, Juan
气孔保护细胞控制气体交换，使植物能够进行光合作用，但限制植物向环境中的水分流失。在拟南芥中，气孔发育主要受肽配体、膜受体、丝裂原活化蛋白激酶（MAPK）级联和一系列转录因子组成的信号通路控制。气孔谱系的启动需要bHLH转录因子（SPCH）及其伴侣的活性。多种激酶通过磷酸化调节SPCH蛋白的稳定性和功能，但尚未发现拮抗蛋白磷酸酶活性。在这里，我们发现保守的PP2A磷酸酶是拟南芥气孔发育的积极调节因子。我们发现编码PP2A亚基的基因突变导致拟南芥气孔产量降低。遗传分析表明PP2A功能位于SPCH的上游。药理治疗支持PP2A在促进SPCH蛋白稳定性中的作用。我们进一步发现SPCH在体外直接与PP2A-A亚基结合。在植物中，非磷酸化的SPCH蛋白受PP2A活性水平的影响较小。因此，我们的研究表明PP2A可能在气孔发育过程中调控主转录因子SPCH的磷酸化状态。
Stomatal guard cells control gas exchange that allows plant photosynthesis but limits water loss from plants to the environment. In Arabidopsis, stomatal development ismainly controlled by a signaling pathway comprising peptide ligands, membrane receptors, a mitogen-activated protein kinase (MAPK) cascade, and a set of transcription factors. The initiation of the stomatal lineage requires the activity of the bHLH transcription factor SPEECHLESS (SPCH) with its partners. Multiple kinases were found to regulate SPCH protein stability and function through phosphorylation, yet no antagonistic protein phosphatase activities have been identified. Here, we identify the conserved PP2A phosphatases as positive regulators of Arabidopsis stomatal development. We show that mutations in genes encoding PP2A subunits result in lowered stomatal production in Arabidopsis. Genetic analyses place the PP2A function upstream of SPCH. Pharmacological treatments support a role for PP2A in promoting SPCH protein stability. We further find that SPCH directly binds to the PP2A-A subunits in vitro. In plants, nonphosphorylatable SPCH proteins are less affected by PP2A activity levels. Thus, our research suggests that PP2A may function to regulate the phosphorylation status of the master transcription factor SPCH in stomatal development.