Undergraduate Williams College Ann Arbor, Michigan
Body of Abstract: Plant metabolism consists of both primary metabolic pathways required for the maintenance of life and secondary metabolic pathways that have evolved to serve non-essential but beneficial functions. Several plants have evolved the ability to synthesize O-methyl anthranilate from anthranilate, an intermediate in tryptophan biosynthesis. Plants in the Citrus family (Rutaceae) are capable of converting anthranilate to its N-methyl form (like Ruta graveolens, common rue) or to both its N- and O-methyl forms (like Citrus sinensis, sweet orange) through secondary metabolic processes. In R. graveolens, N-methyl anthranilate plays a role in the synthesis of acridone alkaloids, which are suspected to have defensive anti-herbivory functions in plants. We have recently identified a putative anthranilate N-methyltransferase (ANMT) in C. sinensis, which presumably evolved from caffeic acid methyltransferases involved in lignin biosynthesis. Having conducted biochemical studies to characterize the ANMT in R. graveolens, we aim to characterize the kinetics, substrate specificity, and evolutionary history of the C. sinensis ANMT. These findings will expand our knowledge of anthranilate metabolism and the regulation of the anthranilate branchpoint. As citrus orchards are being decimated by citrus greening (Huanglongbing), the study of anthranilate metabolism may be especially important for understanding how Citrus plants defend themselves against insects and bacteria.