engleski

Centromere epigenetics of Tribolium sibling species

The flour beetle Tribolium castaneum and its congener Tribolium freemani are important world-wide pests of stored agricultural products. The two sibling species are able to mate, but produce sterile hybrid progeny in reciprocal crosses. In the context of genetic diversity between closely related species we focused on centromere regions that generally evade genome assemblies due to their repetitive DNA nature. By using the histone H3 sequence as query to search genome databases, in both species we first identified the centromeric histone H3 variants (CENH3), epigenetic hallmarks of active centromeres. T. castaneum cCENH3 and T. freemani fCENH3 H3-like variants share 80% identity in amino acid sequences. Their species-specific N-terminal tails were used to raise antibodies that localized cCENH3 and fCENH3 proteins exclusively to centromeres of T. castaneum and T. freemani, respectively. We further performed ChIP-Seq experiments, which predominantly associated cCENH3 and fCENH3 nucleosomes with a major satellite DNA in each species. As supported by IF-FISH analyses, highly abundant satellite DNAs, TCAST in T. castaneum and TFREE in T. freemani, spread both at pericentromeric and functional centromeric regions of all chromosomes. TCAST and TFREE satellite DNAs account for large fractions (>20%) of their indigenous genomes, and they differ dramatically in monomer unit length (360 bp versus 166 bp) as well as in nucleotide sequence, thus being fundamentally species-specific. In terms of the reproductive isolation between T. castaneum and T. freemani, these findings argue in favor of adaptive evolution of cCENH3 and fCENH3 proteins that might be driven by a response to changes in satellite DNA sequences at centromere loci.

Tribolium ; centromere ; epigenetics

nije evidentirano