All songbirds studied to date have an additional Germline Restricted Chromosome (GRC), which is not present in somatic cells. GRCs show a wide variation in genetic content and little homology between species. To check how this divergence affected the meiotic behavior of the GRC, we examined synapsis, recombination and copy number variation for GRCs in the closely related sand and pale martins (Riparia riparia and R. diluta) in comparison with distantly related estrildid finches. Using immunolocalization of meiotic proteins and FISH with GRC-specific DNA probes, we found a striking similarity in the meiotic behavior of GRCs between martins and estrildid finches despite the millions of years of independent evolution. GRCs are usually present in two copies in female and in one copy in male pachytene cells. However, we detected polymorphism in female and mosaicism in male martins for the number of GRCs. In martin and zebra finch females, two GRCs synapse along their whole length, but recombine predominately at their ends. We suggest that the shared features of the meiotic behavior of GRCs have been supported by natural selection in favor of a preferential segregation of GRCs to the eggs.
Bibliographical noteFunding Information:
We thank M.I. Rodionova for the help in chromosome preparation and the Microscopy Center of the Siberian Department of the Russian Academy of Sciences for granting access to microscopy equipment. This research was funded by the Russian Foundation for Basic Research, grants #18-04-00924 and #19-34-90118 and the Ministry of Science and Higher Education via the Institute of Cytology and Genetics, grant #0324-2019-0042.
© 2020, The Author(s).
- Chromosome Pairing
- DNA Copy Number Variations
- Recombination, Genetic
- Sex Chromosomes/genetics
PubMed: MeSH publication types
- Research Support, Non-U.S. Gov't
- Journal Article