Unravelling Jasmonate Signalling Cascades

FiglogoarabidopsisjasmonJasmonates are plant-specific signalling molecules, found throughout the plant kingdom, that steer diverse physiological and developmental processes.

Their best-known function is to signal attacks by arthropod herbivores or necrotrophic pathogens, both locally and systemically, leading to mounted defences, including the activation of specialized metabolism. The central module of the jasmonate (JA) signalling cascade has largely been discovered in Arabidopsis thaliana, and found to be conserved across the plant kingdom. Bioactive JAs, such as jasmonoyl-isoleucine, are perceived by the E3 ubiquitin ligase SCFCOI1, which targets the JAZ repressor proteins for degradation. This event causes the release of the transcription factor MYC2, thereby activating the first wave of JA-induced gene expression. Within this cascade, the JAZ proteins play a central role. JAZ proteins have been demonstrated to interact with a broad array of transcription factors that each control specific downstream processes. Recruitment of the co-repressor TOPLESS unveiled a mechanism for JAZ-mediated gene repression. The presence of JAZ proteins was also found to be regulated by interactions with proteins from other hormonal signalling pathways, revealing modes of hormonal crosstalk. 

However, many questions remain regarding the targets, specificity, function, and regulation of the JA perception and primary signalling module. Our research focuses on this crucial molecular complex. We are interested in discovering novel interactors and revealing how they impinge on this central module and regulate its activity. AP-MS is being used in Arabidopsis, Medicago and tomato to map the dynamics of the assembly of this protein complex, to characterize post-translational protein modification of its members in response to jasmonate signalling and to identify novel interactors of regulatory proteins potentially involved in jasmonate signalling. Thereby, we endeavour to expose new mechanistic principles in the modulation of gene expression and the regulation of protein activity and stability, which may lead to novel paradigms in our understanding of how hormonal signals are translated towards the regulation of plant growth and metabolism.

 

Model of JA perception and early signalling machinery