title: Molecular basis of evolutionary events that shaped the hardness locus in diploid and polyploid wheat species (Triticum and Aegilops).
abstract: The Hardness (Ha) locus controls grain hardness in hexaploid wheat (Triticum aestivum) and its relatives (Triticum and Aegilops species) and represents a classical example of a trait whose variation arose from gene loss after polyploidization. In this study, we investigated the molecular basis of the evolutionary events observed at this locus by comparing corresponding sequences of diploid, tertraploid, and hexaploid wheat species (Triticum and Aegilops). Genomic rearrangements, such as transposable element insertions, genomic deletions, duplications, and inversions, were shown to constitute the major differences when the same genomes (i.e., the A, B, or D genomes) were compared between species of different ploidy levels. The comparative analysis allowed us to determine the extent and sequences of the rearranged regions as well as rearrangement breakpoints and sequence motifs at their boundaries, which suggest rearrangement by illegitimate recombination. Among these genomic rearrangements, the previously reported Pina and Pinb genes loss from the Ha locus of polyploid wheat species was caused by a large genomic deletion that probably occurred independently in the A and B genomes. Moreover, the Ha locus in the D genome of hexaploid wheat (T. aestivum) is 29 kb smaller than in the D genome of its diploid progenitor Ae. tauschii, principally because of transposable element insertions and two large deletions caused by illegitimate recombination. Our data suggest that illegitimate DNA recombination, leading to various genomic rearrangements, constitutes one of the major evolutionary mechanisms in wheat species.
authors.affiliation: Institut National de la Recherche Agronomique-Centre de Cooperation Internationale en Recherche Agronomique pour le Développement, Biotrop, F-34398 Montpellier Cedex 5, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Chantret
authors.forename: Jérôme
authors.initials: J
authors.lastname: Salse
authors.forename: François
authors.initials: F
authors.lastname: Sabot
authors.forename: Sadequr
authors.initials: S
authors.lastname: Rahman
authors.forename: Arnaud
authors.initials: A
authors.lastname: Bellec
authors.forename: Bastien
authors.initials: B
authors.lastname: Laubin
authors.forename: Ivan
authors.initials: I
authors.lastname: Dubois
authors.forename: Carole
authors.initials: C
authors.lastname: Dossat
authors.forename: Pierre
authors.initials: P
authors.lastname: Sourdille
authors.forename: Philippe
authors.initials: P
authors.lastname: Joudrier
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Gautier
authors.forename: Laurence
authors.initials: L
authors.lastname: Cattolico
authors.forename: Michel
authors.initials: M
authors.lastname: Beckert
authors.forename: Sébastien
authors.initials: S
authors.lastname: Aubourg
authors.forename: Jean
authors.initials: J
authors.lastname: Weissenbach
authors.forename: Michel
authors.initials: M
authors.lastname: Caboche
authors.forename: Michel
authors.initials: M
authors.lastname: Bernard
authors.forename: Philippe
authors.initials: P
authors.lastname: Leroy
authors.forename: Boulos
authors.initials: B
authors.lastname: Chalhoub
mesh_terms: D002874:Chromosome Mapping; D004251:DNA Transposable Elements / Q000235:genetics; D004171:Diploidy; D019143:Evolution, Molecular; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D018745:Genome, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics; D011123:Polyploidy; D011995:Recombination, Genetic / Q000235:genetics*; D014908:Triticum / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004251:DNA Transposable Elements; D010940:Plant Proteins