Arabidopsis Basic Helix-Loop-Helix Transcription Factors MYC2 MYC3 and MYC4 Regulate Glucosinolate Biosynthesis Insect Performance and Feeding Behavior

摘要

Arabidopsis thaliana plants fend off insect attack by constitutive and inducible production of toxic metabolites, such as glucosinolates (). A triple mutant lacking MYC2, MYC3, and MYC4, three basic helix-loop-helix transcription factors that are known to additively control jasmonate-related defense responses, was shown to have a highly reduced expression of biosynthesis genes. The myc2 myc3 myc4 (myc234) triple mutant was almost completely devoid of and was extremely susceptible to the generalist herbivore Spodoptera littoralis. On the contrary, the specialist Pieris brassicae was unaffected by the presence of and preferred to feed on wild-type plants. In addition, lack of in myc234 drastically modified S. littoralis feeding behavior. Surprisingly, the expression of MYB factors known to regulate biosynthesis genes was not altered in myc234, suggesting that MYC2/MYC3/MYC4 are necessary for direct transcriptional activation of biosynthesis genes. To support this, chromatin immunoprecipitation analysis showed that MYC2 binds directly to the promoter of several biosynthesis genes in vivo. Furthermore, yeast two-hybrid and pull-down experiments indicated that MYC2/MYC3/MYC4 interact directly with -related MYBs. This specific MYC–MYB interaction plays a crucial role in the regulation of defense secondary metabolite production and underlines the importance of in shaping plant interactions with adapted and nonadapted herbivores.