Spiridonova L.N., Surmach S.G.
Genetika 2025; 61(8): 48-61
The intragenomic polymorphism of the OCA2 gene fragment (approximately 4800 bp), encoding the transmembrane P-protein associated with feather coloration in birds, was studied for the first time in seven Far Eastern owl species: Eurasian eagle-owl (Bubo bubo), Blakiston's fish owl (Bubo (Ketupa) blakistoni), snowy owl (Bubo (Nyctea) scandiacus), long-eared owl (Asio otus), Ural owl (Strix uralensis), oriental scops owl (Otus sunia), and Japanese scops owl (Otus semitorques). The intragenomic variability of OCA2 within this diverse group of Strigiformes ranged from 0.005 in B. bubo to 0.014 in O. sunia, exceeding interspecific values for this gene in the genera Falco and Cygnus (0.000-0.006). Genetic distances between genera within the family Strigidae varied widely (0.022-0.048) but were comparable to those observed in the family Accipitridae (0.015-0.040). For the first time, pseudogenization of the OCA2 gene was detected in some of the studied species, based on comparisons of exon regions of the coding gene and various copies of its pseudogenes. Two pseudogene variants were identified in O. semitorques, three in B. (N.) scandiacus, and eight in B. bubo. High levels of intragenomic polymorphism were observed for OCA2 pseudogenes, driven by numerous single mutations, insertions, and deletions of varying lengths. Deep genetic differentiation was found for certain species pairs controversially assigned to the same genus, corresponding to intergeneric levels of genetic distances for OCA2 in other avian orders. This provides additional arguments in favor of their generic independence at the genus level: O. sunia - O. semitorques (0.031), B. bubo - B. (K.) blakistoni (0.024), and B. (K.) blakistoni - B. (N.) scandiacus (0.022). The phylogenetic reconstruction of Strigiformes and other taxa based on the OCA2 gene largely aligns with findings derived from other molecular markers.
