Methyl jasmonate induces pigmentation and flavonoid gene expression in petunia corollas: A possible role in wound response

We have previously shown that gibberellic acid (GA) plays an important role in the regulation of anthocyanin synthesis and flavonoid gene transcription in developing petunia corollas. The aim of the present work was to examine the possible role of methyl jasmonate (JA‐Me) in the regulation of these processes. JA‐Me induces anthocyanin biosynthesis and chalcone synthase (chs) and dihydroflavonol 4‐reductase (dfr) gene expression in detached corollas. JA‐Me promoted β‐glucuronidase (GUS) activity in corollas of transgenic plants carrying the gus gene driven by a chs promoter, indicating that it acts at the level of transcription initiation. Whereas chs induction by GA₃ started after 5 h and was durable. that of JA‐Me was more rapid but transient. Anthocyanin synthesis was induced by wounding and this effect was enhanced by JA‐Me. Wounding also induced an increase in jasmonate content in detached corollas. The kinetics of chs and dfr mRNA accumulation following wounding was similar to that caused by JA‐Me but not to that caused by GA₃. Our results suggest that JA‐Me does not play a role in the natural developmental regulation of corolla pigmentation but that it may mediate wound‐induced changes in flavonoid gene transcription.