A fungal-responsive MAPK cascade regulates phytoalexin biosynthesis in Arabidopsis

Dongtao Ren, Yidong Liu, Kwang Yeol Yang, Ling Han, Guohong Mao, Jane Glazebrook, Shuqun Zhang

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297 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)5638-5643
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - Apr 8 2008
Externally publishedYes


  • Botrytis cinerea
  • Camalexin biosynthesis
  • Defense signaling
  • Fungal resistance


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