title: Identification and Characterization of Maize salmon silks Genes Involved in Insecticidal Maysin Biosynthesis.
abstract: The century-old maize (Zea mays) salmon silks mutation has been linked to the absence of maysin. Maysin is a C-glycosyl flavone that, when present in silks, confers natural resistance to the maize earworm (Helicoverpa zea), which is one of the most damaging pests of maize in America. Previous genetic analyses predicted Pericarp Color1 (P1; R2R3-MYB transcription factor) to be epistatic to the sm mutation. Subsequent studies identified two loci as being capable of conferring salmon silks phenotypes, salmon silks1 (sm1) and sm2 Benefitting from available sm1 and sm2 mapping information and from knowledge of the genes regulated by P1, we describe here the molecular identification of the Sm1 and Sm2 gene products. Sm2 encodes a rhamnosyl transferase (UGT91L1) that uses isoorientin and UDP-rhamnose as substrates and converts them to rhamnosylisoorientin. Sm1 encodes a multidomain UDP-rhamnose synthase (RHS1) that converts UDP-glucose into UDP-l-rhamnose. Here, we demonstrate that RHS1 shows unexpected substrate plasticity in converting the glucose moiety in rhamnosylisoorientin to 4-keto-6-deoxy glucose, resulting in maysin. Both Sm1 and Sm2 are direct targets of P1, as demonstrated by chromatin immunoprecipitation experiments. The molecular characterization of Sm1 and Sm2 described here completes the maysin biosynthetic pathway, providing powerful tools for engineering tolerance to maize earworm in maize and other plants.
authors.affiliation: Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, Ohio 43210 Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210.
authors.forename: María Isabel
authors.identifier: 0000-0002-1395-9646
authors.initials: MI
authors.lastname: Casas
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, Santa Fe S2002LRK, Argentina.
authors.forename: María Lorena
authors.initials: ML
authors.lastname: Falcone-Ferreyra
authors.affiliation: Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Nan
authors.identifier: 0000-0002-7283-6347
authors.initials: N
authors.lastname: Jiang
authors.affiliation: Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, Ohio 43210 Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210.
authors.forename: María Katherine
authors.identifier: 0000-0002-2791-182X
authors.initials: MK
authors.lastname: Mejía-Guerra
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, Rosario, Santa Fe S2002LRK, Argentina.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Rodríguez
authors.affiliation: Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Tyler
authors.identifier: 0000-0002-9467-8909
authors.initials: T
authors.lastname: Wilson
authors.affiliation: Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Jacob
authors.initials: J
authors.lastname: Engelmeier
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, Santa Fe S2002LRK, Argentina.
authors.forename: Paula
authors.identifier: 0000-0002-3194-4683
authors.initials: P
authors.lastname: Casati
authors.affiliation: Center for Applied Plant Sciences, The Ohio State University, Columbus, Ohio 43210 Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210 grotewold.1@osu.edu.
authors.forename: Erich
authors.initials: E
authors.lastname: Grotewold
mesh_terms: D047369:Chromatin Immunoprecipitation; D005419:Flavonoids / Q000096:biosynthesis* / Q000378:metabolism*; D005960:Glucosides / Q000096:biosynthesis* / Q000378:metabolism*; D047311:Luteolin / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014539:Uridine Diphosphate Sugars / Q000378:metabolism; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D005960:Glucosides; D010940:Plant Proteins; D014539:Uridine Diphosphate Sugars; C114429:maysin; C022183:UDP-rhamnose; C057912:homoorientin; D047311:Luteolin