Newly synthesized wheat allohexaploids display progenitor-dependent meiotic stability and aneuploidy but structural genomic additivity.
To understand key mechanisms leading to stabilized allopolyploid species, we characterized the meiotic behaviour of wheat allohexaploids in relation to structural and genetic changes. For that purpose, we analysed first generations of synthetic allohexaploids obtained through interspecific hybridization, followed by spontaneous chromosome doubling, between several genotypes of Triticum turgidum and Aegilops tauschii wheat species, donors of AB and D genomes, respectively. As expected for these Ph1 (Pairing homoeologous 1) gene-carrying allopolyploids, chromosome pairing at metaphase I of meiosis essentially occurs between homologous chromosomes. However, the different synthetic allohexaploids exhibited progenitor-dependent meiotic irregularities, such as incomplete homologous pairing, resulting in univalent formation and leading to aneuploidy in the subsequent generation. Stability of the synthetic allohexaploids was shown to depend on the considered genotypes of both AB and D genome progenitors, where few combinations compare to the natural wheat allohexaploid in terms of regularity of meiosis and euploidy. Aneuploidy represents the only structural change observed in these synthetic allohexaploids, as no apparent DNA sequence elimination or rearrangement was observed when analysing euploid plants with molecular markers, developed from expressed sequence tags (ESTs) as well as simple sequence repeat (SSR) and transposable element sequences.
Organization and Evolution of Plant Genomes, Unité de Recherche en Génomique Végétale, 91057 Evry Cedex, France.
Imen
I
Mestiri
Véronique
V
Chagué
Anne-Marie
AM
Tanguy
Cecile
C
Huneau
Virginie
V
Huteau
Harry
H
Belcram
Olivier
O
Coriton
Boulos
B
Chalhoub
Joseph
J
Jahier
D000782:Aneuploidy; D023902:Chromosome Pairing / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D019143:Evolution, Molecular; D015321:Gene Rearrangement / Q000235:genetics; D005819:Genetic Markers; D018745:Genome, Plant / Q000235:genetics*; D006824:Hybridization, Genetic; D008540:Meiosis / Q000235:genetics*; D008677:Metaphase / Q000235:genetics; D016133:Polymerase Chain Reaction; D011123:Polyploidy; D013045:Species Specificity; D014908:Triticum / Q000166:cytology* / Q000235:genetics*
D018744:DNA, Plant; D005819:Genetic Markers