Chromosome Synapsis and Recombination in Male-Sterile and Female-Fertile Interspecies Hybrids of the Dwarf Hamsters (Phodopus, Cricetidae)

Abstract

Hybrid sterility is an important step in the speciation process. Hybrids between dwarf hamsters Phodopus sungorus and P. campbelli provide a good model for studies in cytological and genetic mechanisms of hybrid sterility. Previous studies in hybrids detected multiple abnormalities of spermatogenesis and a high frequency of dissociation between the X and Y chromosomes at the meiotic prophase. In this study, we found that the autosomes of the hybrid males and females underwent paring and recombination as normally as their parental forms did. The male hybrids showed a significantly higher frequency of asynapsis and recombination failure between the heterochromatic arms of the X and Y chromosomes than the males of the parental species. Female hybrids as well as the females of the parental species demonstrated a high incidence of centromere misalignment at the XX bivalent and partial asynapsis of the ends of its heterochromatic arms. In all three karyotypes, recombination was completely suppressed in the heterochromatic arm of the X chromosome, where the pseudoautosomal region is located. We propose that this recombination pattern speeds up divergence of the X- and Y-linked pseudoautosomal regions between the parental species and results in their incompatibility in the male hybrids.

Relationship between meiotic behaviour and fertility in backcross-1 derivatives of the [(Gossypium hirsutum × G. thurberi)2 × G. longicalyx] trispecies hybrid

“…Globally, the number of BC2 seeds produced per backcross was negatively correlated with the average number of univalents at Metaphase I (R = -0.67, P < 0.05) indicating a deleterious role of unpaired chromosomes on the fertility of the hybrid plants. This is in accordance with Bikchurina et al (2018) who reported that univalents impair pollen fertility and seed production.…”

Hybridization between subterranean tuco-tucos (Rodentia, Ctenomyidae) with contrasting phylogenetic positions

“…Despite the description of several hybrids among rodent species, in which chromosome painting has been performed on the parental species in a few cases, painting was not applied to the hybrids. There appear to be only two exceptions namely Phodopus sungorus and P. campbelli, which have the same chromosomal number (2n = 28) 40,41 , and Microtus arvalis (2n = 46) and M. levis (2n = 54), in which the difference in numbers is due to one fission and three fusions 29,42 . Thus, so far, hybrids of C. minutus and C. flamarioni demonstrate the greatest chromosomal reorganization among viable rodent hybrids.…”

Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex

“…For example, pairing of X and Y chromosomes is more adversely affected than that of autosomes during the prophase I in male hybrids between Campbell's dwarf hamster and the Djungarian hamster [72]. a recent work has clarified that the autosomes of male hybrids between these hamster species undergo pairing and recombination normally as their parental forms do, but the heterochromatic arms of the X and Y chromosomes show a high frequency of asynapsis and recombination failure [73]. It was proposed that asynapsis of heterospecific chromosomes in prophase I may provide a recurrently evolving trigger for the meiotic arrest of interspecific F1 hybrids of mice [74,75].…”