Role of Arabidopsis bHLH transcription factors MYC2, MYC3 and MYC4in defense against herbivory

www.unil.ch/reymondlab

A B C D

Predators

Indirect defenses

Direct defenses

Induction of defense genes

Emission of volatile compounds

Induced defenses in response to herbivory

TFs

Jasmonate pathway

JA signalling

from Staswick, 2008

Stimulus (wound, herbivore)

Spodoptera littoralis

WT coi1-1 WT coi1-1

Spodoptera littoralis

JA signalling is crucial for defense against herbivory

The majority of insect-responsive genes are not induced in coi1-1

7 days of larval feeding

Reymond et al. (2004) Plant Cell

Role of bHLH transcription factors MYC2, MYC3 and MYC4

Growth of Spodoptera littoralis larvae on myc mutants

Fernandez-Calvo et al. (2011) Plant Cell

Sub-family of Arabidopsis bHLH transcription factors

Trancriptome analysis of myc234 mutant

Schweizer et al. (2013) Plant Cell

The majority of highly dowregulated genes in myc234 are GS-pathway genes

Glucosinolate pathway genes are downregulated in myc234 mutant

Glucosinolates are defense compounds in Brassicaceae

Aliphatic-GS Indole-GS

Rapid profiling of intact glucosinolates

Glauser et al. (2012) Phytochem Anal

UHPLC-QTOFMS

Glucosinolate levels are highly reduced in myc234 mutants

ConstitutiveInduced (S. littoralis)

Schweizer et al. (2013) Plant Cell

MYCs control GS accumulation in seeds

Two-choice assay

The specialist P. brassicae prefersglucosinolate-containing plants

Oviposition

Contrasting insect performance on Arabidopsis glucosinolate mutants

Schweizer et al. (2013) Plant Cell

Change of feeding behaviour of a generalist herbivore

Schweizer et al. (2013) Plant Cell

Non-uniform ditribution of GSSchroff et al. (2008) PNAS

Are GS-related MYBs controlled MYC2,3,4?

downregulated genes

MYC2MYC3MYC4

MYC2MYC3MYC4

?

?

MYC2,3,4 physically interact with MYBs

Schweizer et al. (2013) Plant Cell

but: GS-related MYBs donot interact with JAZs

MYC2 binds to the promoter of GS biosynthesis genes

ChIP-seq analysis of MYC2-GFP plants

CYP79B3 (Atg22330) SOT16 (Atg74100)

Consensus MYC binding site(G-box element)

GS biosynthesis genescontain MYC- and MYB-binding sites

Schweizer et al. (2013) Plant Cell

Model for MYC234-dependent activation of glucosinolate genes

defense againstgeneralist herbivores

Role of other insect-inducible transcription factors

S. littoralis performance

S. littoralis-induced genes

Schweizer et al. (2013) Front. Plant Sci.

A hierarchy of transcription factors

MYBs

glucosinolates

Acknowledgements

Fabian Schweizer

Gaetan Glauser & Ted TurlingsSPSW Chemical Analysis Service, Neuchâtel

Patricia Fernandez-Calvo & Roberto SolanoDept. of Plant Molecular Genetics, Madrid

Mark Zander, Mathew Lewsey & Joe EckerThe Salk Institute, La Jolla (CA)