title: Patterns of sequence divergence and evolution of the S orthologous regions between Asian and African cultivated rice species.
abstract: A strong postzygotic reproductive barrier separates the recently diverged Asian and African cultivated rice species, Oryza sativa and O. glaberrima. Recently a model of genetic incompatibilities between three adjacent loci: S(1)A, S(1) and S(1)B (called together the S(1) regions) interacting epistatically, was postulated to cause the allelic elimination of female gametes in interspecific hybrids. Two candidate factors for the S(1) locus (including a putative F-box gene) were proposed, but candidates for S(1)A and S(1)B remained undetermined. Here, to better understand the basis of the evolution of regions involved in reproductive isolation, we studied the genic and structural changes accumulated in the S(1) regions between orthologous sequences. First, we established an 813 kb genomic sequence in O. glaberrima, covering completely the S(1)A, S(1) and the majority of the S(1)B regions, and compared it with the orthologous regions of O. sativa. An overall strong structural conservation was observed, with the exception of three isolated regions of disturbed collinearity: (1) a local invasion of transposable elements around a putative F-box gene within S(1), (2) the multiple duplication and subsequent divergence of the same F-box gene within S(1)A, (3) an interspecific chromosomal inversion in S(1)B, which restricts recombination in our O. sativa×O. glaberrima crosses. Beside these few structural variations, a uniform conservative pattern of coding sequence divergence was found all along the S(1) regions. Hence, the S(1) regions have undergone no drastic variation in their recent divergence and evolution between O. sativa and O. glaberrima, suggesting that a small accumulation of genic changes, following a Bateson-Dobzhansky-Muller (BDM) model, might be involved in the establishment of the sterility barrier. In this context, genetic incompatibilities involving the duplicated F-box genes as putative candidates, and a possible strengthening step involving the chromosomal inversion might participate to the reproductive barrier between Asian and African rice species.
authors.affiliation: Plant Genome and Development Laboratory (UMR 5096-CNRS-IRD-UPVD), Institut de Recherche pour le Développement, Montpellier, France. romain.guyot@ird.fr
authors.forename: Romain
authors.initials: R
authors.lastname: Guyot
authors.forename: Andrea
authors.initials: A
authors.lastname: Garavito
authors.forename: Frédérick
authors.initials: F
authors.lastname: Gavory
authors.forename: Sylvie
authors.initials: S
authors.lastname: Samain
authors.forename: Joe
authors.initials: J
authors.lastname: Tohme
authors.forename: Alain
authors.initials: A
authors.lastname: Ghesquière
authors.forename: Mathias
authors.initials: M
authors.lastname: Lorieux
mesh_terms: D000349:Africa; D000383:Agriculture; D001208:Asia; D020029:Base Pairing / Q000235:genetics; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics; D019143:Evolution, Molecular; D044783:F-Box Proteins / Q000235:genetics; D020131:Genes, Duplicate / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D056426:Genetic Loci / Q000235:genetics; D014644:Genetic Variation; D058977:Molecular Sequence Annotation; D012275:Oryza / Q000235:genetics*; D020161:Physical Chromosome Mapping; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004251:DNA Transposable Elements; D044783:F-Box Proteins