Purdue-NWAFU Joint Research Center, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA.
Environ Microbiol. 2017 May;19(5):1959-1974. doi: 10.1111/1462-2920.13710. Epub 2017 Apr 10.
Appressorium formation plays a critical role in Magnaporthe oryzae. Mst50 is an adapter protein of the Mst11-Mst7-Pmk1 cascade that is essential for appressorium formation. To further characterize its functions, affinity purification was used to identify Mst50-interacting proteins (MIPs) in this study. Two of the MIPs are Mst11 and Mst7 that are known to interact with Mst50 for Pmk1 activation. Surprisingly, two other MIPs are Mck1 and Mkk2 that are the upstream kinases of the Mps1 pathway. Domain deletion analysis showed that the sterile alpha-motif of Mst50 but not the Ras-association domain was important for its interaction with Mck1 and responses to cell wall and oxidative stresses. The mst50 mutant was reduced in Mps1 activation under stress conditions. MIP11 encodes a RACK1 protein that also interacted with Mck1. Deletion of MIP11 resulted in defects in cell wall integrity, Mps1 phosphorylation and plant infection. Furthermore, Mst50 interacted with histidine kinase Hik1, and the mst50 mutant was reduced in Osm1 phosphorylation. These results indicated that Mst50 is involved in all three MAPK pathways in M. oryzae although its functions differ in each pathway. Several MIPs are conserved hypothetical proteins and may be involved in responses to various signals and crosstalk among signaling pathways.
附着胞的形成在稻瘟病菌中起着关键作用。Mst50 是 Mst11-Mst7-Pmk1 级联反应的衔接蛋白，对于附着胞的形成是必需的。为了进一步研究其功能，本研究采用亲和纯化方法鉴定了 Mst50 的相互作用蛋白（MIPs）。其中两个 MIPs 是 Mst11 和 Mst7，已知它们与 Mst50 相互作用以激活 Pmk1。令人惊讶的是，另外两个 MIPs 是 Mck1 和 Mkk2，它们是 Mps1 途径的上游激酶。结构域缺失分析表明，Mst50 的不育α基序而不是 Ras 结合结构域对于其与 Mck1 的相互作用和对细胞壁及氧化应激的反应是重要的。在应激条件下，mst50 突变体中 Mps1 的激活减少。MIP11 编码一种 RACK1 蛋白，也与 Mck1 相互作用。MIP11 的缺失导致细胞壁完整性、Mps1 磷酸化和植物感染缺陷。此外，Mst50 与组氨酸激酶 Hik1 相互作用，mst50 突变体中 Osm1 的磷酸化减少。这些结果表明，Mst50 参与了稻瘟病菌中的所有三种 MAPK 途径，尽管其在每条途径中的功能不同。一些 MIPs 是保守的假设蛋白，可能参与对各种信号的反应和信号通路之间的串扰。
