Evolutionary and biochemical genomic investigation of three gene families encoding enzymes of plant specialized metabolism.

Abstract

Plants have evolved, and are still actively evolving the ability to make specialized metabolites to aid them in interacting with their environment. Recent genomic studies have revealed many proteins that are related to enzymes known to be involved in the biosynthesis of these compounds. However, the majority of these homologous proteins have not yet been assigned a biochemical activity. Sequence comparisons of the proteins with known function can identify residues essential for substrate binding and catalysis. Subsequently, this information can be used to increase our understanding of how plants evolve the capability to produce new compounds and to identify the functions of unknown proteins. The dissertation describes methodologies to perform biochemical genomic characterization of the functions of members of three protein families known as the BAHD acyltransferases, SABATH methyltransferases, and terpene synthases. The approach begins with computer based phylogenetic analysis to identify the members of these three families in both <italic>Arabidopsis thaliana</italic> and <italic>Clarkia breweri</italic>. This data is then correlated with chemical and transcription profiling to identify potential biosynthetic enzymes. Further experiments include the isolation of the cDNA, heterologous expression of the protein in <italic>E. coli</italic>, and enzymatic assays of the resulting proteins.