Variability of the chromosomal distribution of Ty3-gypsy retrotransposons in the populations of two wild Triticeae species

Abstract

Here, we report data on the population variability of Ty3-gypsy retrotransposons in genomes of Aegilops speltoides (2n = 2x = 14) and Hordeum spontaneum (2n = 2x = 14). Based on the sequence analysis or reverse transcriptase (RT) gene conserved domains, two groups of elements were recognized. Elements of Group I show relatedness to such a known element as RIRE2, and elements of Group II show relatedness to Fatima and Cereba. Cloned and sequenced fragments of Ty3-gypsy RT that show the closest relatedness to known elements (Fatima and RIRE2) were used as probes for fluorescent in situ hybridization (FISH). FISH experiments revealed mini-cluster organization of the Ty3-gypsy element chromosomal distribution in wild Triticeae species. Mini-clusters can be divided into three categories according to their intraspecific stability: (i) stable species-specific clusters that are mainly adjusted to the regions of rRNA genes; (ii) variable clusters that represent 68% of clusters in the genome of Ae. speltoides and 20% in the genome of H. spontaneum; and (iii) population-specific clusters that are mainly insertions into centromeric central domains of different chromosomes and the majority of these insertions were detected in populations with hot, dry environments. Significant interpopulation variability of Ty3-gypsy element chromosomal distribution in the Ae. speltoides genome contrasts with the uniform genome of H. spontaneum and may reflect differences in adaptive strategies between investigated species.