title: Genetic characterization and expression analysis of wheat (Triticum aestivum) line 07OR1074 exhibiting very low polyphenol oxidase (PPO) activity.
abstract: Characterized novel mutations present at Ppo loci account for the substantial reduction of the total kernel PPO activity present in a putative null Ppo - A1 genetic background. Wheat (Triticum aestivum) polyphenol oxidase (PPO) contributes to the time-dependent discoloration of Asian noodles. Wheat contains multiple paralogous and orthologous Ppo genes, Ppo-A1, Ppo-D1, Ppo-A2, Ppo-D2, and Ppo-B2, expressed in wheat kernels. To date, wheat noodle color improvement efforts have focused on breeding cultivars containing Ppo-D1 and Ppo-A1 alleles conferring reduced PPO activity. A major impediment to wheat quality improvement is a lack of additional Ppo alleles conferring reduced kernel PPO. In this study, a previously reported very low PPO line, 07OR1074, was found to contain a novel allele at Ppo-A2 and null alleles at the Ppo-A1 and Ppo-D1 loci. To examine the impact of each mutation upon kernel PPO, populations were generated from crosses between 07OR1074 and the hard white spring wheat cultivars Choteau and Vida. Expression analysis using RNA-seq demonstrated no detectable Ppo-A1 transcripts in 07OR1074 while Ppo-D1 transcripts were present at less than 10% of that seen in Choteau and Vida. Novel markers specific for the Ppo-D1 and Ppo-A2 mutations discovered in 07OR1074, along with the Ppo-A1 STS marker, were used to screen segregating populations. Evaluation of lines indicated a substantial genotypic effect on PPO with Ppo-A1 and Ppo-D1 alleles contributing significantly to total PPO in both populations. These results show that the novel mutations in Ppo-A1 and Ppo-D1 present in 07OR1074 are both important to lowering overall wheat seed PPO activity and may be useful to produce more desirable and marketable wheat-based products.
authors.affiliation: Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT, 59717-3150, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Hystad
authors.forename: J M
authors.initials: JM
authors.lastname: Martin
authors.forename: R A
authors.initials: RA
authors.lastname: Graybosch
authors.forename: M J
authors.initials: MJ
authors.lastname: Giroux
mesh_terms: D000483:Alleles; D001947:Breeding; D004156:Catechol Oxidase / Q000235:genetics* / Q000378:metabolism; D003433:Crosses, Genetic; D018744:DNA, Plant / Q000235:genetics; D005819:Genetic Markers; D009154:Mutation; D012639:Seeds / Q000201:enzymology*; D014908:Triticum / Q000201:enzymology / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D005819:Genetic Markers; D004156:Catechol Oxidase