Metabolomics of Phytoalexin-Dependent Anthracnose Resistance in Sorghum

Sorghum responds to invasion of both pathogenic and non-pathogenic fungi by the induction of 3-deoxyanthocyanidin (3-DA) phytoalexins. Although several studies have demonstrated the antimicrobial nature of these compounds and shown that these are rapidly induced in resistant lines when exposed to pathogens, their biosynthetic pathway and its regulation remains obscure. The structural similarities between 3-DAs and flavan-4-ols, the precursors of the red phlobaphene pigments found in sorghum and maize, suggests that these compounds may be synthesized via a common or overlapping pathway. We are interested in genetic characterization of the biosynthetic steps of the pathway that are induced upon fungal ingress. We showed that a mutable allele of an R2R3 MYB transcription factor encoded by yellowseed1 is partially defective in the synthesis of phytoalexins. Metabolite profiling of near isogenic resistant and susceptible lines of sorghum further confirmed phytoalexin-dependent resistance (Ibraheem et al., 1010. Genetics. http://www.genetics.org/content/184/4.cover-expansion). Results from the metabolic profiling of flavonoid compounds in sorghum germplasm will be presented. Genetic dissection of phytoalexin pathway in different maize mutants is being performed. Comparison of maize and sorghum flavonoid phytoalexin metabolic pathways will be discussed in the context of anthracnose disease resistance.