Variable organization of repeats and hidden diversity of XY sex chromosomes in Pentatomidae true Bugs (Hemiptera) revealed through comparative genomic hybridization

Abstract

Sex chromosomes have independently evolved in various species, displaying unique evolutionary patterns, including differentiation, degeneration, and repetitive DNA accumulation. Pentatomidae hemipterans are characterized by a highly conserved diploid number of 2n = 14 with a XX/XY sex chromosome system, i.e. 2n = 14, 12 A + XY. Thus, it represents an interesting group for investigating the reorganization of repeats in conserved karyotypes, i.e. the absence of large chromosomal rearrangements. Using comparative genomic hybridization (CGH) with male and female genomic DNAs (gDNA), this study examined a total of 25 Pentatomidae species to uncover repetitive DNA dynamics and their role in chromosome differentiation, especially sex chromosome differentiation. New karyotype data for nine species reinforces the chromosomal stasis in Pentatomidae for macro-chromosomal structure. However, significant variability in repetitive DNA patterns on autosomes and sex chromosomes has been revealed despite the karyotypic conservation. Autosomal signals varied in intensity and distribution, with some species exhibiting terminal enrichment of repeats, while others displayed dispersed patterns. Sex chromosomes showed distinct hybridization patterns, with the Y chromosome exhibiting more significant variability compared to the X. These findings emphasize the dynamic nature of sex chromosomes and suggest further studies combining genomic sequencing and cytogenetics to uncover sequences and the mechanisms behind their evolution.