title: Tandem repeats on an eco-geographical scale: outcomes from the genome of Aegilops speltoides.
abstract: The chromosomal pattern of tandem repeat fractions of repetitive DNA is one of the most important characteristics of a species. In the present research, we aimed to detect and evaluate the level of intraspecific variability in the chromosomal distribution of species-specific Spelt 1 and Aegilops-Triticum-specific Spelt 52 tandem repeats in Aegilops speltoides and in closely related diploid and polyploid species. There is a distinct eco-geographical gradient in Spelt 1 and Spelt 52 blocks abundance in Ae. speltoides. In marginal populations, the number of Spelt 1 chromosomal blocks could be 12-14 times lower than in the center of the species distribution. Also, in related diploid species, the abundance of Spelt 52 correlates with evolutionary proximity to Ae. speltoides. Finally, the B- and G-genomes of allopolyploid wheats have Spelt 1 chromosomal distribution patterns similar to those of the types of Ae. speltoides with poor and rich contents of Spelt 1, respectively. The observed changes in numbers of blocks of Spelt 1 and Spelt 52 tandem repeats along the eco-geographical gradient may due to their depletion in the marginal populations as a result of increased recombination frequency under stressful conditions. Alternatively, it may be accumulation of tandem repeats in conducive climatic/edaphic environments in the center of the species' geographical distribution. Anyway, we observe a bidirectional shift of repetitive DNA genomic patterns on the population level leading to the formation of population-specific chromosomal patterns of tandem repeats. The appearance of a new chromosomal pattern is considered an important factor in promoting the emergence of interbreeding barriers.
authors.affiliation: Laboratory of Plant Molecular Cytogenetics, Institute of Evolution, University of Haifa, Mount Carmel, Haifa 31905, Israel. raskina@research.haifa.ac.il
authors.forename: Olga
authors.initials: O
authors.lastname: Raskina
authors.forename: Leonid
authors.initials: L
authors.lastname: Brodsky
authors.forename: Alexander
authors.initials: A
authors.lastname: Belyayev
mesh_terms: D001947:Breeding; D032461:Chromosomes, Plant / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D004171:Diploidy; D014644:Genetic Variation; D005828:Genetics, Population; D018745:Genome, Plant / Q000235:genetics*; D005838:Genotype; D005843:Geography; D017404:In Situ Hybridization, Fluorescence; D019083:Mediterranean Region; D008877:Middle East; D010802:Phylogeny; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D011110:Polymorphism, Genetic; D011123:Polyploidy; D013045:Species Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*; D014908:Triticum / Q000145:classification / Q000235:genetics
chemical_list: D018744:DNA, Plant