Characterization Of Jasmonic Acid Response Mutant Ber15

As a plant hormone, jasmonic acid plays a very important role in regulating plantdefense reponses. However, relatively little is known about the molecular mechanisms ofsignaling transduction of Jasmonic acid (JA). A small molecule, bestatin, an inhibitor ofsome aminopeptidases, potently activates JA-induced defense genes expression in themodel systems of tomato and Arabidopsis. We have employed bestatin as a smallmolecular chemical tool to dissect jasmonic acid signaling in Arabidopsis and identifieda collection of bestatin response (ber) mutants, ber15 is one of these mutants that areresistant to the inhibitory effect of bestatin on root elongation. Subsequent investigationrevealed that ber15 is less sensitive to applied jasmonic acid in term of root growthinhibition, suggesting that the BER15 gene play a role in JA signaling. Map-basedcloning of BER15 demonstrated that the mutant phynotype of ber15 is caused by asingle-nucelotide mutation of AT3g30180, which encodes a cytochrome P450monooxygenase with bifunction that possesses BR C-6 oxidase and BL synthase activitywhich acts as a key enzyme in brassinolide synthesis.The successful cloning of BER15not only shows that the chemical genetics system based on bestatin is feasible and willprovide a new method in researching for JA signaling pathway,but also demonstratedthat this gene is concerned to two important agricultural properties, growth potentialand resistance. There is no doubt that BER15 will be a good candidate to gene-melioration to breed niusanceless vegetable. Further functional analysis of BER15 willbroaden our knowledge of the interaction mechanism between brassinolide biosynthesisand JA signaling.