The mitogen-activated protein kinase (MAPK) cassette of the cell wall integrity (CWI) pathway is primarily responsible for orchestrating changes of cell wall. However, functions of this cassette in other cellular processes are not well understood. Here, we found that the Botrytis cinerea mutant of MAPK kinase (BcMkk1) displays more serious defects in mycelial growth, conidiation, responses to cell wall and oxidative stresses, but possesses less reduced virulence than the mutants of its upstream (BcBck1) and downstream (BcBmp3) kinases. Interestingly, BcMkk1, but not BcBck1 and BcBmp3, negatively regulates production of oxalic acid (OA) and activity of extracellular hydrolases (EHs) that are proposed to be virulence factors of B. cinerea. Moreover, we obtained evidence that BcMkk1 negatively controls OA production via impeding phosphorylation of the Per-Arnt-Sim (PAS) kinase BcRim15 by the Ser/Thr kinase BcSch9. In addition, the fungal Pro40 homolog BcPro40 was found to interact simultaneously with three MAPKs, implying that BcPro40 is a scaffold protein of the CWI pathway in B. cinerea. Taken together, results of this study reveal that BcMkk1 negatively modulates virulence via suppressing OA biosynthesis in B. cinerea, which provides novel insight into conserved and species-specific functions of the MAPK kinase in fungi.

细胞壁完整性（CWI）途径的丝裂原活化蛋白激酶（MAPK）盒主要负责协调细胞壁的变化。但是，该盒在其他细胞过程中的功能尚不清楚。在这里，我们发现MAPK激酶的灰葡萄孢菌突变体（BcMkk1）在菌丝体生长，分生，对细胞壁和氧化应激的反应中表现出更严重的缺陷，但比其上游（BcBck1）和下游（BcBck1）的突变体具有更少的降低的毒性。 BcBmp3）激酶。有趣的是，BcMkk1而非BcBck1和BcBmp3负调节草酸（OA）的产生和细胞外水解酶（EHs）的活性，而草酸被认为是B的毒力因子。灰质。此外，我们获得的证据表明，BcMkk1通过阻止Per / Arnt-Sim（PAS）激酶BcRim15的Ser / Thr激酶BcSch9磷酸化来负面控制OA的产生。此外，发现真菌Pro40同源物BcPro40与三个MAPK同时相互作用，这表明BcPro40是B中CWI途径的支架蛋白。灰质。两者合计，这项研究的结果表明，BcMkk1通过抑制B中的OA生物合成对毒力进行负调节。灰质，为真菌中MAPK激酶的保守和物种特异性功能提供了新颖的见解。