In eukaryotes, MAPK scaffold proteins are crucial for regulating the function of MAPK cascades. However, only a few MAPK scaffold proteins have been reported in plants, and the molecular mechanism through which scaffold proteins regulate the function of the MAPK cascade remains poorly understood. Here, we identified GhMORG1, a GhMKK6-GhMPK4 cascade scaffold protein that positively regulates the resistance of cotton to Fusarium oxysporum. GhMORG1 interacted with GhMKK6 and GhMPK4, and the overexpression of GhMORG1 in cotton protoplasts dramatically increased the activity of the GhMKK6-GhMPK4 cascade. Quantitative phosphoproteomics was used to clarify the mechanism of GhMORG1 in regulating disease resistance, and thirty-two proteins were considered as the putative substrates of the GhMORG1-dependent GhMKK6-GhMPK4 cascade. These putative substrates were involved in multiple disease resistance processes, such as cellular amino acid metabolic processes, calcium ion binding and RNA binding. The kinase assays verified that most of the putative substrates were phosphorylated by the GhMKK6-GhMPK4 cascade. For functional analysis, nine putative substrates were silenced in cotton, respectively. The resistance of cotton to F. oxysporum was decreased in the substrate-silenced cottons. These results suggest that GhMORG1 regulates several different disease resistance processes by facilitating the phosphorylation of GhMKK6-GhMPK4 cascade substrates. Taken together, these findings reveal a new plant MAPK scaffold protein and provide insights into the mechanism of plant resistance to pathogens.

中文翻译：

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支架蛋白GhMORG1通过促进MKK6-MPK4级联反应增强棉花对尖孢镰刀菌的抗性。

在真核生物中，MAPK支架蛋白对于调节MAPK级联的功能至关重要。然而，在植物中仅报道了少数MAPK支架蛋白，而支架蛋白通过其调节MAPK级联功能的分子机制仍知之甚少。在这里，我们确定了GhMORG1，一种GhMKK6-GhMPK4级联支架蛋白，可正向调节棉花对尖孢镰刀菌的抗性。GhMORG1与GhMKK6和GhMPK4相互作用，并且棉花原生质体中GhMORG1的过表达极大地增加了GhMKK6-GhMPK4级联的活性。定量磷酸化蛋白质组学用于阐明GhMORG1调节抗病性的机制，并且32种蛋白质被认为是依赖GhMORG1的GhMKK6-GhMPK4级联的推定底物。这些假定的底物参与了多种疾病抗性过程，例如细胞氨基酸代谢过程，钙离子结合和RNA结合。激酶测定证实，大多数推定的底物被GhMKK6-GhMPK4级联磷酸化。为了进行功能分析，分别在棉花中沉默了九种假定的底物。在底物沉默的棉花中，棉花对尖孢镰刀菌的抗性降低。这些结果表明，GhMORG1通过促进GhMKK6-GhMPK4级联底物的磷酸化来调节几种不同的抗病过程。综上所述，这些发现揭示了一种新的植物MAPK支架蛋白，并提供了植物对病原体抗性机制的见解。例如细胞氨基酸的代谢过程，钙离子结合和RNA结合。激酶测定证实，大多数推定的底物被GhMKK6-GhMPK4级联磷酸化。为了进行功能分析，分别在棉花中沉默了九种假定的底物。在底物沉默的棉花中，棉花对尖孢镰刀菌的抗性降低。这些结果表明，GhMORG1通过促进GhMKK6-GhMPK4级联底物的磷酸化来调节几种不同的抗病过程。综上所述，这些发现揭示了一种新的植物MAPK支架蛋白，并提供了植物对病原体抗性机制的见解。例如细胞氨基酸的代谢过程，钙离子结合和RNA结合。激酶测定证实，大多数推定的底物被GhMKK6-GhMPK4级联磷酸化。为了进行功能分析，分别在棉花中沉默了九种假定的底物。在底物沉默的棉花中，棉花对尖孢镰刀菌的抗性降低。这些结果表明，GhMORG1通过促进GhMKK6-GhMPK4级联底物的磷酸化来调节几种不同的抗病过程。综上所述，这些发现揭示了一种新的植物MAPK支架蛋白，并提供了植物对病原体抗性机制的见解。为了进行功能分析，分别在棉花中沉默了九种假定的底物。在底物沉默的棉花中，棉花对尖孢镰刀菌的抗性降低。这些结果表明，GhMORG1通过促进GhMKK6-GhMPK4级联底物的磷酸化来调节几种不同的抗病过程。综上所述，这些发现揭示了一种新的植物MAPK支架蛋白，并提供了植物对病原体抗性机制的见解。为了进行功能分析，分别在棉花中沉默了九种假定的底物。在底物沉默的棉花中，棉花对尖孢镰刀菌的抗性降低。这些结果表明，GhMORG1通过促进GhMKK6-GhMPK4级联底物的磷酸化来调节几种不同的抗病过程。综上所述，这些发现揭示了一种新的植物MAPK支架蛋白，并提供了植物对病原体抗性机制的见解。