The transcription factor MYC2 shapes plant defense responses in Arabidopsisupon Pieris rapae herbivory


Abstract: Plants are capable to defend themselves against a broad range of attackers. Once anattacker has passed constitutive barriers, several plant hormones are produced leading to a localand systemic defense response that will counteract the invader. It is known that the hormonejasmonic acid (JA) plays a major role in the defence against insects and necrotrophic pathogens.JA can activate different sets of JA-responsive genes, depending on other (attacker specific)signaling molecules that are simultaneously produced upon attack (e.g. the phytohormonesabscisic acid (ABA) and ethylene (ET)). Transcription factors (TFs) play an important role in theregulation of the differential JA responses. In Arabidopsis thaliana the TF MYC2 was identifiedas key regulator of wounding specific JA-regulated responses. MYC2 gene expression is activatedby both JA and ABA and repressed by ET. In contrast, several ERF-type TFs such as AtERF14,ERF1 and ORA59 are activated by JA and ET and repressed by ABA. The MYC2 TF is believedto be important in defense against insects. Upon caterpillar feeding, a plant mutated in MYC2shows a shift in its JA-dependent transcriptional profile compared to the wild type. In wild-typeArabidopsis, the MYC2-dependent VSP2-branch of the JA response is activated, while in mutantsimpaired in MYC2 (jin1 mutants) the ERF-dependent PDF1.2-branch is activated. Although thisshift in transcription pattern appeared to have no direct influence on the growth of larvae of thesmall cabbage white (Pieris rapae), caterpillar choice tests revealed that P. rapae larvae have apreference for myc2 mutant plants over wild-type plants. This indicates that activation of MYC2-dependent JA responses plays a role in deterring insect herbivores such as P. rapae, resulting inless damage to the plant.

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