Characterization of the Genes Responsible for C-Glycosyl Flavone Formation in Maize

MA. ISABEL CASAS; MARÍA KATHERINE MEJÍA-GUERRA; MARÍA LORENA FALCONE-FERREYRA; EDUARDO JOSE RODRIGUEZ; PAULA CASATI; ERICH GROTEWOLD

Pheasant Run, St. Charles

Conferencia; 55th Maize Genetics Conference; 2013

Maysin is a C-glycosyl flavone (CGF) shown to confer natural resistance against corn earworm (Helicoverpa zea) (CEW), a maize pest responsible for high yield losses per season. Maysin accumulates in silks, where it exerts its biocidal action by reducing CEW growth and development; and to a lesser extent in pericarps, the outermost layer of the maize kernel. This research aims to determine the identity and function of the gene products involved in the last steps of maysin biosynthesis. Previous studies on QTL analysis have determined that the loci corresponding to the R2R3-MYB transcription factor P1 (or its duplicate P2) and the loci salmon silks 1 (SM1), salmon silks 2 (SM2) and recessive enhancer of maysin 1 (REM1) are involved in the formation and accumulation of this CGF in silks. In addition, these studies also suggested possible functions for SM2 being a rhamnosyl transferase, and SM1 being involved in the last dehydration step towards maysin. However, there has been no activity proposed for REM1, nor where it is placed in the pathway and what might the identity of the genes involved in these conversions be. Our search for possible candidate genes had the following criteria: They had to be included in the mapping intervals for those loci, their putative functions had to be similar to those proposed to SM2 and SM1 and they had to be highly expressed in P1-rr silks and pericarps. This candidate gene analysis yielded strong candidates for SM2 and SM1, which are being biochemically characterized. This project is funded in part by NSF IOS-1125620.