Location: Chemistry Research Unit
2013 Annual Report
2. Confirm the identity of previously unknown metabolites through de novo synthesis.
3. Study biosynthetic pathways and biological functions for a subset of novel plant metabolites.
Metabolomics: Identification of inducible bioactive plant metabolites: Two novel acidic sesquiterpenoid phytoalexins, termed zealexin A4 and zealexin B3, have been discovered in maize. Zealexin A4 exhibits significant antimicrobial activity against a range a fungal pathogens including Southern Leaf Blight (Cochliobolus heterostrophus) and Aspergillus flavus. A transposon insertion mutant in the gene AntherEar2, encoding an ent-copalyl diphosphate synthase, was identified in the maize W22 background. Maize plants homozygous for this mutation completely lack production of all kauralexin diterpenoid phytoalexins following insect and pathogen attack. Propagated seeds are currently being used in greenhouse and field experiments to examine altered resistance phenotypes with naturally occurring fungal and insect pests. Whole transcriptome shotgun sequencing, termed RNA-seq, of seedling scutella tissue revealed candidate a type II kaurene synthase for the kauralexin biosynthetic pathway. Preliminary analysis of this transposon insertion mutant supports the role of this enzyme as a second step in the pathway. Further functional characterization of this inducible maize kaurene synthase is currently underway.