Asano Tomoya, Nguyen Thi Hang-Ni, Yasuda Michiko, Sidiq Yasir, Nishimura Kohji, Nakashita Hideo, Nishiuchi Takumi
Institute for Gene Research, Advanced Science Research Center, Kanazawa University, Takaramachi, Kanazawa, Ishikawa, Japan.
Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, Japan.
J Exp Bot. 2020 Mar 25;71(6):2085-2097. doi: 10.1093/jxb/erz556.
The genome of Arabidopsis encodes more than 60 mitogen-activated protein kinase kinase (MAPKK) kinases (MAPKKKs); however, the functions of most MAPKKKs and their downstream MAPKKs are largely unknown. Here, MAPKKK δ-1 (MKD1), a novel Raf-like MAPKKK, was isolated from Arabidopsis as a subunit of a complex including the transcription factor AtNFXL1, which is involved in the trichothecene phytotoxin response and in disease resistance against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (PstDC3000). A MKD1-dependent cascade positively regulates disease resistance against PstDC3000 and the trichothecene mycotoxin-producing fungal pathogen Fusarium sporotrichioides. MKD1 expression was induced by trichothecenes derived from Fusarium species. MKD1 directly interacted with MKK1 and MKK5 in vivo, and phosphorylated MKK1 and MKK5 in vitro. Correspondingly, mkk1 mutants 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 and flg22. Finally, quantitative phosphoproteomics suggested that an MKD1-dependent cascade controlled phosphorylation of a disease resistance protein, SUMO, and a mycotoxin-detoxifying enzyme. Our findings suggest that the MKD1-MKK1/MKK5-MPK3/MPK6-dependent signaling cascade is involved in the full immune responses against both bacterial and fungal infection.
拟南芥基因组编码60多种丝裂原活化蛋白激酶激酶（MAPKK）激酶（MAPKKKs）；然而，大多数MAPKKKs及其下游MAPKKs的功能在很大程度上尚不清楚。在这里，MAPKKK δ-1（MKD1），一种新型的类Raf MAPKKK，从拟南芥中分离出来，作为一个复合物的亚基，该复合物包括转录因子AtNFXL1，其参与单端孢霉烯植物毒素反应和对细菌病原体丁香假单胞菌番茄致病变种DC3000（PstDC3000）的抗病性。一个依赖MKD1的级联反应正向调节对PstDC3000和产生单端孢霉烯霉菌毒素的真菌病原体串珠镰刀菌的抗病性。MKD1的表达由镰刀菌属产生的单端孢霉烯诱导。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转基因植物对串珠镰刀菌表现出增强的易感性。MKD1是T-2毒素和flg22完全激活两种丝裂原活化蛋白激酶（MPK3和MPK6）所必需的。最后，定量磷酸蛋白质组学表明，一个依赖MKD1的级联反应控制着一种抗病蛋白SUMO和一种霉菌毒素解毒酶的磷酸化。我们的研究结果表明，MKD1-MKK1/MKK5-MPK3/MPK6依赖的信号级联反应参与了对细菌和真菌感染的完全免疫反应。
