MAP kinases MPK9 and MPK12 are preferentially expressed in guard cells and positively regulate ROS-mediated ABA signaling
MAP kinases MPK9 and MPK12 are preferentially expressed in guard cells and positively regulate ROS-mediated ABA signaling
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DOI：
10.1073/pnas.0907205106
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发表时间：
2009-12-01
影响因子：
11.1
通讯作者：
Kwak, June M.
中科院分区：
文献类型：
--
作者：
Jammes, Fabien;Song, Charlotte;Kwak, June M.
活性氧 (ROS) 介导保卫细胞中的脱落酸 (ABA) 信号传导。为了从遗传学上剖析保卫细胞 ABA-ROS 信号传导，使用细胞类型特异性功能基因组学方法来鉴定 2 个 MAPK 基因：MPK9 和 MPK12，它们在保卫细胞中优先且高度表达。为了为其功能提供遗传证据，分离了在这些基因中携带有害点突变的拟南芥单 TILLING 突变体和双 TILLING 突变体。还生成了基于 RNAi 的基因沉默植物系，其中两个基因同时沉默。仅在其中 1 个基因中携带突变的突变体没有表现出任何改变的表型，表明这些基因的功能冗余。 ABA 诱导的气孔关闭在 2 个独立的 RNAi 系中受到严重损害，其中 MPK9 和 MPK12 转录本均显着沉默。与此结果一致，mpk9-1/12-1 双突变体表现出增强的蒸腾水分损失以及对 ABA 和 H2O2 不敏感的气孔反应。此外，ABA 和钙未能激活 mpk9-1/12-1 保卫细胞中的阴离子通道，表明这 2 个 MPK 在保卫细胞 ABA 信号传导中作用于阴离子通道的上游。 MPK12-YFP 融合构建体挽救了 mpk9-1/12-1 ABA 不敏感的气孔反应表型，证明该表型是由突变引起的。 MPK12 蛋白定位于细胞质和细胞核，ABA 和 H2O2 处理可增强 MPK12 的蛋白激酶活性。总之，这些结果提供了遗传证据，表明 MPK9 和 MPK12 在 ROS 下游发挥作用，积极调节保卫细胞 ABA 信号传导。
Reactive oxygen species (ROS) mediate abscisic acid (ABA) signaling in guard cells. To dissect guard cell ABA-ROS signaling genetically, a cell type-specific functional genomics approach was used to identify 2 MAPK genes, MPK9 and MPK12, which are preferentially and highly expressed in guard cells. To provide genetic evidence for their function, Arabidopsis single and double TILLING mutants that carry deleterious point mutations in these genes were isolated. RNAi-based gene-silencing plant lines, in which both genes are silenced simultaneously, were generated also. Mutants carrying a mutation in only 1 of these genes did not show any altered phenotype, indicating functional redundancy in these genes. ABA-induced stomatal closure was strongly impaired in 2 independent RNAi lines in which both MPK9 and MPK12 transcripts were significantly silenced. Consistent with this result, mpk9-1/12-1 double mutants showed an enhanced transpirational water loss and ABA- and H2O2-insensitive stomatal response. Furthermore, ABA and calcium failed to activate anion channels in guard cells of mpk9-1/12-1, indicating that these 2 MPKs act upstream of anion channels in guard cell ABA signaling. An MPK12-YFP fusion construct rescued the ABA-insensitive stomatal response phenotype of mpk9-1/12-1, demonstrating that the phenotype was caused by the mutations. The MPK12 protein is localized in the cytosol and the nucleus, and ABA and H2O2 treatments enhance the protein kinase activity of MPK12. Together, these results provide genetic evidence that MPK9 and MPK12 function downstream of ROS to regulate guard cell ABA signaling positively.