MKD1, a novel MAPKKK, is required for disease resistance against Fusarium Species.

MAPKKK delat-1 （MKD1）是一种新型的raf样MAPKKK，作为包括拟南芥转录因子AtNFXL1的复合体的亚基被分离出来。mkd1依赖性级联正调控对PstDC3000和产毛霉毒素真菌病原体镰刀菌的抗病能力。MKD1在体内直接与MKK1和MKK5相互作用，并在体外磷酸化MKK1和MKK5。相应地，mkk1突变体和MKK5RNAi转基因植株对孢子毛线虫的易感性增强。MKD1是T-2毒素完全激活两个mapk （MPK3和MPK6）所必需的。最后，定量磷酸化蛋白质组学显示，mkd1依赖级联控制了一种抗病蛋白、sumo和一种真菌毒素解毒酶的磷酸化。我们的研究结果表明，MKD1-MKK1/MKK5-MPK3/ mpk6依赖的信号级联在植物对细菌和真菌植物病原体的免疫应答中起重要作用。

MAPKKK delat-1 (MKD1), a novel Raf-like MAPKKK, was isolated as a subunit of a complex including the Arabidopsis transcription factor AtNFXL1. An MKD1-dependent cascade positively regulates disease resistance against PstDC3000 and the trichothecene mycotoxin-producing fungal pathogen Fusarium sporotrichioides. MKD1 directly interacted with MKK1 and MKK5 in vivo, and phosphorylated MKK1 and MKK5 in vitro. Correspondingly, mkk1 mutant and MKK5RNAi transgenic plants showed enhanced susceptibility to F. sporotrichioides. MKD1 was required for full activation of two MAPKs (MPK3 and MPK6) by the T-2 toxin. Finally, quantitative phosphoproteomics revealed that an MKD1-dependent cascade controlled phosphorylation of a disease resistance protein, SUMOs, and a mycotoxin-detoxifying enzyme. Our findings reveal that the MKD1-MKK1/MKK5-MPK3/MPK6-dependent signalling cascade plays an important role in plant immune responses against both bacterial and fungal phytopathogens.