Graduate Student University of Florida Clermont, Florida
Body of Abstract: Glucosinolates are amino acid-derived defense compounds in Brassicales. They are categorized as aliphatic or aromatic, depending on the precursor amino acid. 2-phenylethylglucosinolate (2PE) is a widely found aromatic glucosinolate, where its biosynthesis starts from the single chain elongation of phenylalanine to produce homophenylalanine. A recent study showed that Arabidopsis CYP79F1, known to function in aliphatic glucosinolate biosynthesis, catalyzes homophenylalanine to produce phenylethylacetaldoxime, the precursor of 2PE. Thus, we hypothesized that 2PE biosynthesis and its regulation may occur through the machinery needed for aliphatic glucosinolates rather than aromatic/indolic glucosinolates. However, our organ-specific profiling of glucosinolates revealed that accumulation patterns of 2PE differ from aliphatic glucosinolates in Arabidopsis. 2PE were detected in select organs such as seeds, yet absent in roots, whereas aliphatic glucosinolates accumulate in all organs including seeds and roots. Glucosinolate profiles of cyp83a1 and cyp83b1 mutants indicated that CYP83A1 and CYP83B1 function redundantly in catalyzing phenylethylacetaldoxime, with CYP83A1 playing a more significant role in 2PE biosynthesis than CYP83B1. Given that myb28 single mutant accumulates significantly reduced levels of 2PE and myb28 myb29 double mutant were absent of 2PE, biosynthesis of 2PE is sufficiently regulated by MYB28 and MYB29, known regulators of aliphatic glucosinolate biosynthesis. Furthermore, our feeding study demonstrated that the chain elongation of phenylalanine to produce homophenylalanine is not a rate limiting step in 2PE biosynthesis.