Substrate Preference and Function of Salicylic Acid Methyltransferase in Dicots

Abstract

Salicylic acid carboxyl methyltransferase (SAMT) and benzoic acid carboxyl methyltransferase (BAMT) are enzymes in plants which catalyze the methylation of salicylic acid (SA) and benzoic acid (BA). These chemicals play an important role in in plant defense against abiotic and biotic stress (SA and MeS), herbivory (BA and MeB, SA and MeS) and pathogen attack (SA and MeS), and are important for pollinator attraction (BA and MeB). ´ SAMT: SSYSLMWLS versus SSYSLQWLS. ´ BAMT: SSYSLHWLS SAMT evolved from a duplication event and a following mutation in the active site of an ancestral BAMT protein, and has since preferred catalyzing SA to methyl salicylate (MeS) over BA to methyl benzoate (MeB). The functionality of SAMT was found to have been maintained in all previously studied dicots.