Mitogen-Activated Protein Kinase Cascade MKK7-MPK6 Plays Important Roles in Plant Development and Regulates Shoot Branching by Phosphorylating PIN1 in Arabidopsis.
Mitogen-Activated Protein Kinase Cascade MKK7-MPK6 Plays Important Roles in Plant Development and Regulates Shoot Branching by Phosphorylating PIN1 in Arabidopsis.
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DOI：
10.1371/journal.pbio.1002550
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发表时间：
2016-09
期刊：
影响因子：
9.8
通讯作者：
Wang Y
中科院分区：
文献类型：
--
作者：
Jia W;Li B;Li S;Liang Y;Wu X;Ma M;Wang J;Gao J;Cai Y;Zhang Y;Wang Y;Li J;Wang Y
有证据表明，丝裂原活化蛋白激酶（MAPK/MPK）信号通路与植物发育的许多方面有关。MAPK级联反应的复杂性不仅对识别植物中的MAPK模块提出了挑战，而且对定义单个模块的具体作用也提出了挑战。到目前为止，我们对MAPK信号传导的了解主要局限于MAPK级联的一个小子集。我们以前的研究已经表征了拟南芥bushy和dwarf 1（bud 1）突变体，其中MAP激酶激酶7（MKK 7）被组成性激活，导致多个表型改变。在这项研究中，我们发现MPK 3和MPK 6是MKK 7在植物中磷酸化的底物。遗传分析表明，MKK 7-MPK 6级联反应特异性地参与了植物地上部分枝、下胚轴向地性、花丝伸长和侧根形成的调控，而MKK 7-MPK 3级联反应主要参与了叶片形态的调控。我们进一步证明，MKK 7-MPK 6级联控制通过磷酸化Ser 337的PIN 1，这影响了木质部薄壁细胞和极性生长素运输的初级茎中的PIN 1的基础定位芽分支。我们的研究结果不仅详细说明了MKK 7-MPK 6级联的功能，而且还揭示了PIN 1磷酸化的新机制，建立了MAPK级联和生长素调控的植物发育之间的分子联系。MKK 7-MPK 6级联在调节生长素相关的发育事件和磷酸化PIN 1中起特定作用，影响其极化并决定拟南芥中的芽分支。MAPK级联在将环境和发育信号转导为适应性和程序性反应中起重要作用。由于MAPK级联的复杂性，揭示MAPK模块的特异性是在高等植物中形成功能完整的信号转导系统的关键。在MAPK信号传导模块中，MAPK激酶（MKKs）是特别重要的，因为它们在MAPK信号传导中充当会聚点和发散点。我们以前的研究已经描述了拟南芥bushy和dwarf 1（bud 1）突变体，其中MAP激酶激酶7（MKK 7）被组成性激活，导致多种生长素相关的发育缺陷。在这里，我们使用bud 1突变体来发现MKK 7下游模块的信号事件。我们的研究结果表明，MPK 6和MPK 3是MKK 7的两个主要下游靶标。此外，我们发现MKK 7-MPK 6级联磷酸化PIN 1的Ser 337（S337）位点，影响PIN 1的极性定位，从而修改芽分支。我们的研究结果详细说明了MKK 7-MPK 6级联的功能，并解释了MKK 7-MPK 6信号通路如何调节极性生长素运输，以确定拟南芥中的芽分支。
Emerging evidences exhibit that mitogen-activated protein kinase (MAPK/MPK) signaling pathways are connected with many aspects of plant development. The complexity of MAPK cascades raises challenges not only to identify the MAPK module in planta but also to define the specific role of an individual module. So far, our knowledge of MAPK signaling has been largely restricted to a small subset of MAPK cascades. Our previous study has characterized an Arabidopsis bushy and dwarf1 (bud1) mutant, in which the MAP Kinase Kinase 7 (MKK7) was constitutively activated, resulting in multiple phenotypic alterations. In this study, we found that MPK3 and MPK6 are the substrates for phosphorylation by MKK7 in planta. Genetic analysis showed that MKK7-MPK6 cascade is specifically responsible for the regulation of shoot branching, hypocotyl gravitropism, filament elongation, and lateral root formation, while MKK7-MPK3 cascade is mainly involved in leaf morphology. We further demonstrated that the MKK7-MPK6 cascade controls shoot branching by phosphorylating Ser 337 on PIN1, which affects the basal localization of PIN1 in xylem parenchyma cells and polar auxin transport in the primary stem. Our results not only specify the functions of the MKK7-MPK6 cascade but also reveal a novel mechanism for PIN1 phosphorylation, establishing a molecular link between the MAPK cascade and auxin-regulated plant development. The MKK7-MPK6 cascade plays a specific role in regulating auxin-related developmental events and phosphorylates PIN1, affecting its polarization and determining shoot branching in Arabidopsis. MAPK cascades play important roles in transducing environmental and developmental signals into adaptive and programmed responses. Because of the complexity of MAPK cascades, revealing the specificity of the MAPK modules is key to forming a functional and fully connected signal transduction system in higher plants. In the MAPK signaling module, MAPK kinases (MKKs) are of particular importance because they serve as the convergence and divergence points in the MAPK signal transduction. Our previous study had characterized an Arabidopsis bushy and dwarf1 (bud1) mutant, in which the MAP Kinase Kinase 7 (MKK7) was constitutively activated, leading to multiple auxin-related developmental defects. Here, we used the bud1 mutant to discover the signaling events of MKK7 downstream modules. Our results demonstrated that MPK6 and MPK3 are two major downstream targets of MKK7. Furthermore, we found that MKK7-MPK6 cascade phosphorylates the Ser 337 (S337) site of PIN1, affecting PIN1’s polar localization and thus modifying shoot branching. Our findings specify the functions of the MKK7-MPK6 cascade and explain how the MKK7-MPK6 signaling pathway regulates polar auxin transport to determine shoot branching in Arabidopsis.
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