The role of Jasmonate-ZIM-Domain proteins in Systemic Immunity
Thesis or dissertation
University of Exeter
Phytohormone signalling has been shown to have crucial and broad roles in plant development and survival. One of these many roles is plant immunity and response to pathogen invasion. Three main hormones salicylic acid (SA), jasmonic acid (JA) and abscisic acid (ABA), have been shown to have a dramatic impact on plant immunity and determining susceptibility or resistance to pathogen attack. Post invasion defence responses are primarily regulated by a SA dependent pathway. SA mediated defence is shown to be compromised by antagonistic action of the JA and ABA signalling pathways. The multifaceted crosstalk between these three hormone signalling pathways dictates plant susceptibility and resistance. In this study we focus on the regulation of the JA signalling pathway, in particular the role of the transcription factor inhibitor, jasmonate-ZIM-domain proteins. An active form of JA, jasmonoyl–isoleucine (JA–Ile) facilitates the interaction between COI1, an F-box protein and various JAZ proteins to form SCF E3 ubiquitin ligase complexes. SCFCOI1 then tags the captive JAZ proteins for ubiquitination by the 26S proteasome, this allows for transcription of early JA-related genes. We challenged A. thaliana strains, with specific JAZ protein insertional mutations, with the model pathogen P. syringae DC3000. From this work we show a role for JAZ proteins in host susceptibility and resistance. In particular we show a decreased ability in P. syringae to proliferate in A. thaliana jaz 7 knockout mutants, as well increased susceptibility to jaz 5/10 deficient mutants. We also identify a positive relationship between coronatine associated gene expression and jaz 5/10 deficient mutants.
MbyRes in Biosciences