Abstract

Genome functioning in hybrids faces inconsistency. This mismatch is manifested clearly in meiosis during chromosome synapsis and recombination. Species with chromosomal variability can be a model for exploring genomic battles with high visibility due to the use of advanced immunocytochemical methods. We studied synaptonemal complexes (SC) and prophase I processes in 44-chromosome intraspecific (Ellobius tancrei × E. tancrei) and interspecific (Ellobius talpinus × E. tancrei) hybrid mole voles heterozygous for 10 Robertsonian translocations. The same pachytene failures were found for both types of hybrids. In the intraspecific hybrid, the chains were visible in the pachytene stage, then 10 closed SC trivalents formed in the late pachytene and diplotene stage. In the interspecific hybrid, as a rule, SC trivalents composed the SC chains and rarely could form closed configurations. Metacentrics involved with SC trivalents had stretched centromeres in interspecific hybrids. Linkage between neighboring SC trivalents was maintained by stretched centromeric regions of acrocentrics. This centromeric plasticity in structure and dynamics of SC trivalents was found for the first time. We assume that stretched centromeres were a marker of altered nuclear architecture in heterozygotes due to differences in the ancestral chromosomal territories of the parental species. Restructuring of the intranuclear organization and meiotic disturbances can contribute to the sterility of interspecific hybrids, and lead to the reproductive isolation of studied species.

Highlights

  • IntroductionGenome integrity is crucial for a species; its specificity is supported by reproductive isolation

  • Genome integrity is crucial for a species; its specificity is supported by reproductive isolation.Hybrid sterility may develop between species or genetically differentiated populations, as a primary or secondary feature of reproductive isolation [1,2,3,4,5]

  • We studied parental mole vole species—E. talpinus (2n = 54, NF = 54), E. tancrei (2n = 54, NF = 56), and another form of E. tancrei (2n = 34, NF = 56)—and F1 hybrids—intraspecific E. tancrei × E. tancrei

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Summary

Introduction

Genome integrity is crucial for a species; its specificity is supported by reproductive isolation. Hybrid sterility may develop between species or genetically differentiated populations, as a primary or secondary feature of reproductive isolation [1,2,3,4,5]. Two genetic materials in a heterozygous admixed genome interact in various compositions [6] and these hybrid states are often referred to as “genomic conflict” [7,8], “genomic shock” [9,10], “genomic stress” [9,11], or “nucleus at war” [12]. Chromosome differences in hybrid meiocytes can manifest as various irregularities in chromosome synapsis, recombination, chromatin landscape, and transcriptional inactivation [21,22,23,24]

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