Assistant Professor Williams College Williamstown, Massachusetts
Body of Abstract: Plants emit a volatile blend of aromatics to attract pollinators and deter herbivores. The volatile methyl anthranilate, which is responsible for the recognizable smell of grape, is synthesized in at least ten plant families and represents a classic example of convergent evolution. Plants including maize, citrus, strawberry, and grape siphon anthranilate away from the tryptophan biosynthetic pathway by methylating it. In response to herbivore damage, maize synthesizes and releases a volatile blend that contains three aromatics: indole, methyl salicylate, and methyl anthranilate. Studies have shown that release of this volatile blend in response to damage from predatory cotton leafworm larvae attracts parasitic wasps, which leads to reduced feeding and the eventual death of the leafworm. Structurally similar methyl salicylate, or wintergreen, is emitted in response to both biotic and abiotic stresses. Phylogenetics and functional genomics have led to the hypothesis that salicylic acid methyltransferases may have evolved to promiscuously accept anthranilate as a substrate and, in turn, produce an evolutionarily advantageous defense volatile. While many plants synthesize methyl anthranilate using a one-step SAM-dependent methyltransferase, grape (Vitis spp.) uses a two-step pathway for methyl anthranilate production. Using transcriptomics and methyl anthranilate abundance across grape varieties to inform candidate gene selection, we are characterizing Vitis methyltransferases in vitro to determine their products and substrate specificity. Findings from this new project may reveal new mechanisms by which methyl anthranilate and other volatile methyl esters are synthesized in grapes.