The Role of JAZs and GABA in Plant Immune Response
Thesis or dissertation
University of Exeter
Jasmonic acid (JA) is a phytohormone with diverse roles in plant; development, growth and immune response. Jasmonic acid ZIM domain repressor (JAZ) proteins are important negative regulators of JA signalling. It has been shown that JAZs play an important role in the immune response of Arabidopsis thaliana to Pseudomonas syringae, as the pathogen seeks to exploit the JA signalling pathway to weaken A. thaliana's immune response. While JA signalling is vital for immune responses to necrotrophic pathogens such as Botrytis cinerea, it is antagonistic to salicylic acid signalling necessary for immune response to biotrophic pathogens such as P. syringae. Through the use of a yeast two hybrid system we sought to identify novel interactors of JAZ proteins to further map the JAZ interactome during pathogen infection and to show that the JAZ proteins interactomes change during pathogen induced stress. We screened cDNA libraries created from RNA transcripts harvested from A. thaliana during P. syringae infection, with a JAZ5 containing bait vector. We identified two putative, novel interactors of JAZ5; GSTF10 and HSC70-1 both of which have roles in plant defense and affect salicylic acid signalling. We also investigated the effect of JAZs on defence against necrotrophs by infecting At-jaz mutants with B. cinerea. We identified At-jaz5/7 and At-jaz7/10 as more susceptible to B. cinerea infection than wild type plants and hypothesized that this may be due to the removal of JAZ splice variants responsible for preventing runaway JA responses. Additionally we sought to further previous work on the role of γ-aminobutyric acid (GABA) in A. thaliana during pathogen infection. GABA has been shown to act as a source of nutrition for P. syringae but can repress pathogenesis genes. Using mass spectrometry we measured the amino acid content of A. thaliana amino acid transporter mutants inoculated with P. syringae as well as investigating the effect of GABA concentrations on P. syringae growth. We found that At-at5g41800/gat-1 plants inoculated with P. syringae and 10mM GABA exhibited significantly lowered P. syringae growth compared to inoculations of P. syringae alone.
MbyRes in Biosciences