Sex chromosomes of the iconic moth Abraxas grossulariata
112 years ago, Doncaster and Raynor published a paper on an interesting mode of inheritance of a light morph (“lacticolor”) in the magpie moth, Abraxas grossulariata, occurring more frequently in females. Based on their observations, they introduced the concept of female heterogamety (i.e. ♀WZ/♂ZZ and derived sex chromosome systems). However, despite the following cytogenetic studies, the sex chromosomes of this iconic species remained unknown. We took advantage of modern methods of molecular cytogenetics and identified and analyzed the chromosomes in this iconic moth and its congener, A. sylvata. The study revealed a pair of molecularly well-differentiated WZ sex chromosomes in both species. Although these species split only around 9.5 million years ago, their W chromosomes differ greatly, and our results suggest their rapid molecular divergence by independent spreading of female-specific repetitive sequences. Our article was selected for the cover story of the June 2018 Issue of the Genes journal:
Zrzavá M., Hladová I., Dalíková M., Šíchová J., Õunap E., Kubíčková S., Marec F. (2018) Sex chromosomes of the iconic moth Abraxas grossulariata (Lepidoptera, Geometridae) and its congener A. sylvata. Genes 9: 279.
The magpie moth, Abraxas grossulariata (photo Andrej Makara) and its sex chromosomes W and Z. (a) The wild-type form of A. grossulariata. (b) WZ bivalent at the pachytene stage of meiotic prophase I. The W chromosome is highlighted by FISH with a W-painting probe (green), clusters of genes for ribosomal RNA (rDNA, red) are immersed into nucleoli (grey circles in the schematic drawing). (c) Mitotic metaphase chromosomes. The W chromosome was identified by FISH with the W-painting probe (not shown). Bar = 10 μm.