fungal-responsive MAPK cascade regulates phytoalexin biosynthesis in Arabidopsis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 14; pp. 5638 - 5643
• Main Authors: Ren, Dongtao, Liu, Yidong, Yang, Kwang-Yeol, Han, Ling, Mao, Guohong, Glazebrook, Jane, Zhang, Shuqun
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 08.04.2008; National Acad Sciences
• Subjects: Arabidopsis; Arabidopsis - microbiology; Arabidopsis Proteins - biosynthesis; Arabidopsis thaliana; Biochemical pathways; Biochemistry; Biological Sciences; Biosynthesis; Botany; Botrytis; Botrytis cinerea; camalexin; Cell death; disease resistance; Enzymes; Flowers & plants; Fungi; Fungi - immunology; Gene expression regulation; Gene Expression Regulation, Plant - immunology; Genes; host-pathogen relationships; Infections; Kinases; MAP Kinase Signaling System - immunology; mitogen-activated protein kinase; Mitogen-Activated Protein Kinase 3 - metabolism; Mitogen-Activated Protein Kinase 6 - metabolism; Pathogens; phytoalexins; Plant Diseases - immunology; Proteins; resistance mechanisms; Seedlings; Sesquiterpenes; signal transduction; Terpenes - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0711301105

Plant recognition of pathogens leads to rapid activation of MPK3 and MPK6, two Arabidopsis mitogen-activated protein kinases (MAPKs), and their orthologs in other species. Here, we report that synthesis of camalexin, the major phytoalexin in Arabidopsis, is regulated by the MPK3/MPK6 cascade. Activation of MPK3/MPK6 by expression of active upstream MAPK kinase (MAPKK) or MAPKK kinase (MAPKKK) was sufficient to induce camalexin synthesis in the absence of pathogen attack. Induction of camalexin by Botrytis cinerea was preceded by MPK3/MPK6 activation, and compromised in mpk3 and mpk6 mutants. Genetic analysis placed the MPK3/MPK6 cascade upstream of PHYTOALEXIN DEFICIENT 2 (PAD2) and PAD3, but independent or downstream of PAD1 and PAD4. Camalexin induction after MPK3/MPK6 activation was preceded by rapid and coordinated up-regulation of multiple genes encoding enzymes in the tryptophan (Trp) biosynthetic pathway, in the conversion of Trp to indole-3-acetaldoxime (IAOx, a branch point between primary and secondary metabolism), and in the camalexin biosynthetic pathway downstream of IAOx. These results indicate that the MPK3/MPK6 cascade regulates camalexin synthesis through transcriptional regulation of the biosynthetic genes after pathogen infection.