Germline-Restricted Chromosomes and Autosomal Variants Revealed by Pachytene Karyotyping of 17 Avian Species

Karyotypes of less than 10% of bird species are known. Using immunolocalization of the synaptonemal complex, the core structure of meiotic chromosomes at the pachytene stage, and centromere proteins, we describe male pachytene karyotypes of 17 species of birds. This method enables higher resolution than the conventional analyses of metaphase chromosomes. We provide the first descriptions of the karyotypes of 3 species (rook, Blyth ’s reed warbler, and European pied flycatcher), correct the published data on the karyotypes of 10 species, and confirm them for 4 species. All passerine species examined have highly conservative karyotypes, 2n = 80–82 with 7 pairs of macrochromosomes (including the ZZ sex chromosome pair which was not unambiguously distinguished from other macrochromosomes in most species) and 33–34 pairs of microchromosomes. In all of them, but not in the common cuckoo, we revealed single copies of the germline-restricted chromosomes varying in size and morphology even between closely related species. This indicates a fast evolution of this additional chromosome. The interspecies differences concern the sizes of the macrochromosomes, morphology of the microchromosomes, and sizes of the centromeres. The pachytene cells of the gouldian finch, brambling, and common linnet contain heteromorphic synap tonemal complexes indicating heterozygosity for inversions or centromere shifts. The European pied flycatcher, gouldian finch, and domestic canary have extended cen...

Source: Cytogenetic and Genome Research - May 20, 2022 Category: Genetics & Stem Cells Source Type: research