title: Functional alleles of the flowering time regulator FRIGIDA in the Brassica oleracea genome.
abstract: BACKGROUND
  Plants adopt different reproductive strategies as an adaptation to growth in a range of climates. In Arabidopsis thaliana FRIGIDA (FRI) confers a vernalization requirement and thus winter annual habit by increasing the expression of the MADS box transcriptional repressor FLOWERING LOCUS C (FLC). Variation at FRI plays a major role in A. thaliana life history strategy, as independent loss-of-function alleles that result in a rapid-cycling habit in different accessions, appear to have evolved many times. The aim of this study was to identify and characterize orthologues of FRI in Brassica oleracea.
  
  
  RESULTS
  We describe the characterization of FRI from Brassica oleracea and identify the two B. oleracea FRI orthologues (BolC.FRI.a and BolC.FRI.b). These show extensive amino acid conservation in the central and C-terminal regions to FRI from other Brassicaceae, including A. thaliana, but have a diverged N-terminus. The genes map to two of the three regions of B. oleracea chromosomes syntenic to part of A. thaliana chromosome 5 suggesting that one of the FRI copies has been lost since the ancient triplication event that formed the B. oleracea genome. This genomic position is not syntenic with FRI in A. thaliana and comparative analysis revealed a recombination event within the A. thaliana FRI promoter. This relocated A. thaliana FRI to chromosome 4, very close to the nucleolar organizer region, leaving a fragment of FRI in the syntenic location on A. thaliana chromosome 5. Our data show this rearrangement occurred after the divergence from A. lyrata. We explored the allelic variation at BolC.FRI.a within cultivated B. oleracea germplasm and identified two major alleles, which appear equally functional both to each other and A. thaliana FRI, when expressed as fusions in A. thaliana.
  
  
  CONCLUSIONS
  We identify the two Brassica oleracea FRI genes, one of which we show through A. thaliana complementation experiments is functional, and show their genomic location is not syntenic with A. thaliana FRI due to an ancient recombination event. This has complicated previous association analyses of FRI with variation in life history strategy in the Brassica genus.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Irwin
authors.forename: Clare
authors.initials: C
authors.lastname: Lister
authors.forename: Eleni
authors.initials: E
authors.lastname: Soumpourou
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Howell
authors.forename: Graham
authors.initials: G
authors.lastname: Teakle
authors.forename: Caroline
authors.initials: C
authors.lastname: Dean
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins; D001937:Brassica / Q000235:genetics* / Q000254:growth & development; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018745:Genome, Plant; D005838:Genotype; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D026801:Synteny
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; C414613:FRI protein, Arabidopsis; D010940:Plant Proteins