Degenerated, Undifferentiated, Rearranged, Lost: High Variability of Sex Chromosomes in Geometridae (Lepidoptera) Identified by Sex Chromatin.

Martina Hejníčková,František Marec,Marharyta Trehubenko,Pavel Potocký,Magda Zrzavá,Martina Dalíková,Svatava Kubíčková,Toomas Tammaru

doi:10.3390/cells10092230

Abstract

Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.

Highlights

IntroductionIt is generally accepted that they originate from a pair of autosomes when one of the homologs has acquired a sex-determining factor [1]
Sex chromosomes represent a rapidly evolving part of the genome
We addressed questions on the use of sex chromatin as a W chromosome marker and as a data source for theories on the W chromosome origin

Summary

Introduction

It is generally accepted that they originate from a pair of autosomes when one of the homologs has acquired a sex-determining factor [1]. This triggers a sequence of events conditioned by the cessation of recombination, leading to the degeneration of a sex-specific sex chromosome, i.e., Y or. The sex-specific chromosome may lose its sex-determining function and disappear, resulting in the X/XX or Z/ZZ sex chromosome system (reviewed, e.g., in the work of [3,4]). New heteromorphic sex chromosomes may arise from a B chromosome, which acquires a sex-determining locus or begins to pair with the X or Z chromosome in the heterogametic sex [5,6]

Methods

Results

Discussion

Conclusion