Maysin biosynthesis in maize: identification and characterization of genes related to salmon silks mutants

FALCONE FERREYRA, M.L.; CASAS, M.I; GROTEWOLD, E; CASATI, P.; NAN, J; RODRIGUEZ, E.

Jacksonville

Congreso; 58th Annual Maize Genetics Conference; 2016

Maysin is a C-glycosyl flavone that presents anti-feedant effects on corn earworm (Helicoverpa zea, CEW), an insect pest that affects maize yield each growing season. Maysin accumulates mainly in silks, and is also found to a lesser extent in pericarps, the outermost layer of the kernel. Salmon silks (sm) mutants display a salmon silk phenotype that also involves browning color after cutting and lack of maysin accumulation. Previous studies showed sm phenotypes to depend on P1 (encoding an R2R3-MYB transcription factor). Although mutant analyses suggested that SM2 has rhamnosyl transferase activity and SM1 is involved in the last dehydration step of maysin formation, the molecular identity of the sm loci remains unknown. Here, we report progress on the molecular characterization of SM1 and SM2, involved in the last steps of maysin biosynthesis. Because P1 is epistatic to SM1 and SM2, mRNA levels in P1-rr and P1-ww pericarps and silks were compared. Candidate genes for SM1 and SM2 were identified from RNA-Seq analysis by applying a discrete set of criteria. Candidate genes were then confirmed using a combination of approaches that include a novel metabolic complementation assay in maize protoplasts. We will present the molecular characterization and enzymatic activities of SM1 and SM2.