title: Nucleotide polymorphism in the wheat transcriptional activator Spa influences its pattern of expression and has pleiotropic effects on grain protein composition, dough viscoelasticity, and grain hardness.
abstract: Storage protein activator (SPA) is a key regulator of the transcription of wheat (Triticum aestivum) grain storage protein genes and belongs to the Opaque2 transcription factor subfamily. We analyzed the sequence polymorphism of the three homoeologous Spa genes in hexaploid wheat. The level of polymorphism in these genes was high particularly in the promoter. The deduced protein sequences of each homoeolog and haplotype show greater than 93% identity. Two major haplotypes were studied for each Spa gene. The three Spa homoeologs have similar patterns of expression during grain development, with a peak in expression around 300 degree days after anthesis. On average, Spa-B is 10 and seven times more strongly expressed than Spa-A and Spa-D, respectively. The haplotypes are associated with significant quantitative differences in Spa expression, especially for Spa-A and Spa-D. Significant differences were found in the quantity of total grain nitrogen allocated to the gliadin protein fractions for the Spa-A haplotypes, whereas the synthesis of glutenins is not modified. Genetic association analysis between Spa and dough viscoelasticity revealed that Spa polymorphisms are associated with dough tenacity, extensibility, and strength. Except for Spa-A, these associations can be explained by differences in grain hardness. No association was found between Spa markers and the average single grain dry mass or grain protein concentration. These results demonstrate that in planta Spa is involved in the regulation of grain storage protein synthesis. The associations between Spa and dough viscoelasticity and grain hardness strongly suggest that Spa has complex pleiotropic functions during grain development.
authors.affiliation: INRA, UMR1095, Genetics, Diversity, and Ecophysiology of Cereals, F-63100 Clermont-Ferrand, France. catherine.ravel@clermont.inra.fr
authors.forename: Catherine
authors.initials: C
authors.lastname: Ravel
authors.forename: Pierre
authors.initials: P
authors.lastname: Martre
authors.forename: Isabelle
authors.initials: I
authors.lastname: Romeuf
authors.forename: Mireille
authors.initials: M
authors.lastname: Dardevet
authors.forename: Redouane
authors.initials: R
authors.lastname: El-Malki
authors.forename: Jacques
authors.initials: J
authors.lastname: Bordes
authors.forename: Nathalie
authors.initials: N
authors.lastname: Duchateau
authors.forename: Dominique
authors.initials: D
authors.lastname: Brunel
authors.forename: François
authors.initials: F
authors.lastname: Balfourier
authors.forename: Gilles
authors.initials: G
authors.lastname: Charmet
mesh_terms: D000595:Amino Acid Sequence; D004548:Elasticity; D005433:Flour; D035264:Flowers / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005903:Gliadin / Q000378:metabolism; D006239:Haplotypes / Q000235:genetics; D006244:Hardness; D015810:Linkage Disequilibrium / Q000235:genetics; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D009711:Nucleotides / Q000235:genetics*; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics; D012639:Seeds / Q000378:metabolism*; D016415:Sequence Alignment; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics; D014908:Triticum / Q000235:genetics*; D014783:Viscosity
chemical_list: D009711:Nucleotides; D010940:Plant Proteins; D015534:Trans-Activators; C105777:storage protein activator; D005903:Gliadin; D009584:Nitrogen