Molecular basis of evolutionary events that shaped the hardness locus in diploid and polyploid wheat species (Triticum and Aegilops).
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.
Chantret
Nathalie
N
Institut National de la Recherche Agronomique-Centre de Cooperation Internationale en Recherche Agronomique pour le Développement, Biotrop, F-34398 Montpellier Cedex 5, France.
Salse
Jérôme
J
Sabot
François
F
Rahman
Sadequr
S
Bellec
Arnaud
A
Laubin
Bastien
B
Dubois
Ivan
I
Dossat
Carole
C
Sourdille
Pierre
P
Joudrier
Philippe
P
Gautier
Marie-Françoise
MF
Cattolico
Laurence
L
Beckert
Michel
M
Aubourg
Sébastien
S
Weissenbach
Jean
J
Caboche
Michel
M
Bernard
Michel
M
Leroy
Philippe
P
Chalhoub
Boulos
B
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*
D004251:DNA Transposable Elements; D010940:Plant Proteins