Identification And Features Of New Components On The JA Pathway

Jasmonate(JA) is an important hormone, which plays essential roles in regulating plant metabolism, development and defense response to herbivore attack and mechanical wounding. Now we have cloned the genes COI1,JAR1,JIN1/MYC2 and CEV1 in JA Signaling pathway. COI1 is an F-box protein, which plays an essential role in regulating defense responses in plants. The JA receptor(s), COI1 substrates and other major players in the JA signal transduction pathway are largely unknown. We have employed JA as an experimental tool to dissect JA signaling through a genetic screening, which yielded a collection of Arabidopsis mutants that are sensitive to the inhibitory effects of JA on root elongation. Further characterization efforts demonstrate that some mutants are defective in various JA-induced responses, which allowed us to classify the mutants into three phenotypic groups: JA-insensitive mutants and JA-hypersensitive mutants. Genetic and phenotypic analyses of the mutants with altered JA responses indicate that we have identified several novel loci involved in JA signaling. We have carried out a genetic screen for Arabidopsis mutants that are deficient in bestain-mediated responses, and obtained some bestatin resistant (ber) mutants, some of which also shows altered JA-response. Reverse genetic screening obtained a T-DNA insertion mutant of Arabidopsis thaliana aspartyl aminopeptidase (DAP1), a homologue of a yeast aminopeptidaseâ… which was strongly inhibited by bestatin. dap1 plants exhibited increased sensibility to bestatin as well as JA. We proposed that DAP1 acts as a new component in the JA signal transduction pathway. Finally, molecular and functional elucidation of our collection of ber mutants and dap1 promises to shed new light on the JA-mediated defense response pathway.