Arabidopsis basic helix-loop-helix transcription factors MYC2, MYC3, and MYC4 regulate glucosinolate biosynthesis, insect performance, and feeding behavior.
Arabidopsis thaliana plants fend off insect attack by constitutive and inducible production of toxic metabolites, such as glucosinolates (GSs). 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 GS biosynthesis genes. The myc2 myc3 myc4 (myc234) triple mutant was almost completely devoid of GS and was extremely susceptible to the generalist herbivore Spodoptera littoralis. On the contrary, the specialist Pieris brassicae was unaffected by the presence of GS and preferred to feed on wild-type plants. In addition, lack of GS in myc234 drastically modified S. littoralis feeding behavior. Surprisingly, the expression of MYB factors known to regulate GS biosynthesis genes was not altered in myc234, suggesting that MYC2/MYC3/MYC4 are necessary for direct transcriptional activation of GS biosynthesis genes. To support this, chromatin immunoprecipitation analysis showed that MYC2 binds directly to the promoter of several GS biosynthesis genes in vivo. Furthermore, yeast two-hybrid and pull-down experiments indicated that MYC2/MYC3/MYC4 interact directly with GS-related MYBs. This specific MYC-MYB interaction plays a crucial role in the regulation of defense secondary metabolite production and underlines the importance of GS in shaping plant interactions with adapted and nonadapted herbivores.
Department of Plant Molecular Biology, University of Lausane, CH-1015 Lausane, Switzerland.
Fabian
F
Schweizer
Patricia
P
Fernández-Calvo
Mark
M
Zander
Monica
M
Diez-Diaz
Sandra
S
Fonseca
Gaétan
G
Glauser
Mathew G
MG
Lewsey
Joseph R
JR
Ecker
Roberto
R
Solano
Philippe
P
Reymond
D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000469:parasitology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000235:genetics; D005247:Feeding Behavior / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D005961:Glucosinolates / Q000096:biosynthesis*; D060434:Herbivory / Q000502:physiology; D007313:Insecta / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000378:metabolism / Q000469:parasitology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D005961:Glucosinolates; C473611:MYC2 protein, Arabidopsis; C473612:MYC3 protein, Arabidopsis; C473613:MYC4 protein, Arabidopsis; D015534:Trans-Activators