Immunocytological Analysis of Meiotic Recombination in the Gray Goose (Anser anser)

Studies on mammals demonstrate wide interspecific variation in the number and distribution of recombination events along chromosomes. Birds represent an interesting model group for comparative analysis of cytological and ecological drivers of recombination rate evolution. Yet, data on variation in recombination rates in birds are limited to a dozen of species. In this study, we used immunolocalization of MLH1, a mismatch repair protein marking mature recombination nodules, to estimate the overall recombination rate and distribution of crossovers along macrochromosomes in female and male meiosis of the gray goose (Anser anser). The average number of MLH1 foci was significantly higher in oocytes than in spermatocytes (73.6 ± 7.8 and 58.9 ± 7.6, respectively). MLH1 foci distribution along individual macrobivalents showed subtelomeric peaks, which were more pronounced in males. Analysis of distances between neighboring MLH1 foci on macrobivalents revealed stronger crossover interference in male meiosis. These data create a framework for future genetic and physical mapping of the gray goose.