Isolation and characterization of a jasmonic acid carboxyl methyltransferase gene from hot pepper(capsicum annuum L.)

Methyl jasmonate, the methyl ester of jasmonic acid, is a volatile plant hormone that acts as an important cellular regulator, mediating diverse developmental processes and defense responses. Methyl jasmonate is synthesized by methylation of jasmonic acid; this reaction is catalyzed by jasmonic acid carboxyl methyltransferase (JMT). Although JMT cDNA had previously been described only forArabidopsis thaliana, here we used PCR to isolate it fromCapsicum annuum L The 389-amino-acid sequence deduced for theJMT gene showed 92% identity to that fromA. thaliana. Southern blot analysis revealed thatJMT is present in the genome as two copies. Our preliminary northern blot detected no JMT transcript, but, through RT-PCR and subsequent Southern blot analysis of products using genespecific probes, we found that transcript levels increased after leaf-wounding. Likewise, 10 µM methyl jasmonate inducedJMT gene expression in leaves. Transcription levels began to increase 10 min after wounding, and were maintained for 1 to 4 h. Moreover, expression of theCaJMT andPIN2 genes was increased by both wounding and MeJA applications, but was not enhanced by treatment with H2O2.