The genome of Arabidopsis thaliana encodes more than 60 MAPKK kinases (MAPKKKs); however, the functions of most MAPKKKs and their downstream MAPKKs are largely unknown. Here, MAPKKK γ-1 (MKD1), a novel Raf-like MAPKKK, was isolated as a subunit of a complex including the Arabidopsis 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). An MKD1-dependent cascade positively regulates disease resistance against PstDC3000 and the trichothecene mycotoxin-producing fungal pathogen Fusarium sporotrichioides. MKD1 expression was induced by some trichothecenes, which are 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, SUMOs, and a mycotoxin-detoxifying enzyme. Our findings suggest that the MKD1-MKK1/MKK5-MPK3/MPK6-dependent signalling cascade is involved in the full immune responses against both bacterial and fungal infection.

中文翻译：

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拟南芥 MAPKKK γ-1 是对细菌和真菌感染的完全免疫所必需的。

拟南芥的基因组编码超过 60 种 MAPKK 激酶（MAPKKKs）；然而，大多数 MAPKKK 及其下游 MAPKK 的功能在很大程度上是未知的。在这里，MAPKKK γ-1 (MKD1)，一种新型 Raf 样 MAPKKK，被分离为一个复合物的亚基，包括拟南芥转录因子 AtNFXL1，它参与单端孢菌素植物毒素反应和对细菌病原体丁香假单胞菌的抗病性光伏。番茄 DC3000 (PstDC3000)。MKD1 依赖性级联正向调节对 PstDC3000 和产生单端孢霉毒素的真菌病原体 Fusarium sporotrichioides 的抗病性。MKD1 表达是由一些来源于镰刀菌属的单端孢菌素诱导的。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 转基因植物显示出增强的对分生孢子菌的易感性。T-2 毒素和 flg22 完全激活两个 MAPK（MPK3 和 MPK6）需要 MKD1。最后，定量磷酸蛋白质组学表明，依赖于 MKD1 的级联控制了抗病蛋白、SUMO 和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 依赖性信号级联参与了针对细菌和真菌感染的完全免疫反应。定量磷酸蛋白质组学表明，依赖于 MKD1 的级联控制了抗病蛋白、SUMO 和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 依赖性信号级联参与了针对细菌和真菌感染的完全免疫反应。定量磷酸蛋白质组学表明，依赖于 MKD1 的级联控制了抗病蛋白、SUMO 和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 依赖性信号级联参与了针对细菌和真菌感染的完全免疫反应。