Autophagy as a consequence of seasonal functions of testis and epididymis in adult male European bison (Bison bonasus, Linnaeus 1758).

The European bison is still an animal endangered with extinction, so by learning factors that regulate its reproduction, we can contribute to the survival of this species. On the other hand, autophagy is a dynamic, lisosomal, and evolutionary conserved process which is essential for animal cell survival, homeostasis, and differentiation. This process was demonstrated in many species and in many organs; however, information on the metabolic course of autophagy in the male reproductive system in seasonally reproducing species is lacking. Therefore, in this study, we examined for the first time several autophagy-related factors (mTOR, ULK1, Atg13, PI3K, beclin1, beclin2, Atg14, Atg5, Atg16L, LC3) in testicular and epididymal tissues obtained from adult male individuals of the European bison. We compared the level of gene expression, protein synthesis, and localization of autophagy-related factors between June, September, and December (before, during, and after reproductive activity, respectively). We confirmed that the induction of autophagy was at the highest level in the period after reproductive activity, i.e., in December, when a significant increase in the gene and protein expression was observed for the majority of these factors, probably to ensure cellular protection. However, autophagy was also clearly marked in September, during the intense spermatogenesis, and this may indicate a great demand for autophagy-related proteins required for the normal development of reproductive cells. Obtained results seem to confirm that autophagy pathway, as a consequence of seasonal reproduction, may control the normal course of spermatogenesis in the male European bison.