Activity and inactivity of moth sex chromosomes in somatic and meiotic cells
Moths and butterflies (Lepidoptera) are the most species-rich group of animals with female heterogamety, females mostly having a WZ, males a ZZ sex chromosome constitution. We studied chromatin conformation, activity, and inactivity of the sex chromosomes in the flour moth Ephestia kuehniella and the silkworm Bombyx mori, using immunostaining with anti-H3K9me2/3, anti-RNA polymerase II, and fluoro-uridine (FU) labelling of nascent transcripts, with conventional widefield fluorescence microscopy and ‘spatial structured illumination microscopy’ (3D-SIM). The Z chromosome is euchromatic in somatic cells and throughout meiosis. It is transcriptionally active in somatic cells and in the postpachaytene stage of meiosis. The W chromosome in contrast is heterochromatic in somatic cells as well as in meiotic cells at pachytene, but euchromatic and transcriptionally active like all other chromosomes at postpachytene. As the W chromosomes are apparently devoid of protein-coding genes, their transcripts must be non-coding. We found no indication of ‘meiotic sex chromosome inactivation’ (MSCI) in the two species.
KeywordsHeterochromatin Sex chromatin Germline-limited activity MSCI Bombyx Ephestia
The skilled help of Conni Reuter (Lübeck, Germany) is gratefully acknowledged. We thank the National BioResource Project of Japan and the Laboratory of Applied Molecular Entomology in Hokkaido University for providing p50 and a hybrid B. mori, respectively.
M.D. and F.M. were supported by grants 17-17211S and 17-1713713S respectively of the Czech Science Foundation. K.S. received support from Kaken No. 16H05050 of the Japan Society for the Promotion of Science (JSPS).
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