Molecular and biochemical characterization of the jasmonic acid methyltransferase gene from black cottonwood (Populus trichocarpa)

A black cottonwood (Populus trichocarpa) gene (PtJMT1) encoding jasmonic acid methyltransferase was isolated and biochemically characterized. Escherichia coli-expressed PtJMT1 was active with both jasmonic acid (JA) and benzoic acid, with the former being a more preferred substrate, to produce their corresponding methyl esters methyl jasmonate (MeJA) and methyl benzoate. Two residues in the active site of PtJMT1 were demonstrated to be critical for determining the relative specific activities of PtJMT1 with these two substrates. A number of biotic stress factors were found to induce the expression of PtJMT1, suggesting that this gene has a role in poplar defense against biotic stresses. Phylogenetic analysis provides further insight into the evolution of JMT genes.