The Bdkrb2 Gene Family Provides a Novel View of Viviparity Adaption in Sebastes schlegelii

Background: Black rockfish ( Sebastes schlegelii ) is a viviparous teleost . In the prior study, we reported a chromosome-level black rockfish genome assembly and proposed that the rockfish ovarian wall has a similar function to the uterus of mammals. In the present study, the well-developed vascular system was observed in the ovary wall and the exterior surface of the egg membrane. Adaptation of the ovary vasculature to the rising needs of the embryos occurs through both vasodilation and neovascularization. Bdkrb2 encodes a receptor for bradykinin. The two play a critical role in the control of vasodilatation by regulating NO production. Results: Eight Bdkrb2 genes were identified in the black rockfish genome. These genes are located on chromosome 14, which are arranged in a tandem array, forming a gene cluster spanning 50 kb. Protein structure prediction, phylogenetic analysis, and tissue expression pattern analysis was done to clarify the relationship of the Bdkrb2 genes and a preliminary exploration of function was conducted. The results show that the eight Bdkrb2 genes evolved two kinds of protein structure and three kinds of tissue expression pattern. Furthermore, some have a relatively high expression in ovarian wall, especially in stages of pre-fertilization and pre-hatching. Conclusions: Our study characterizes eight Bdkrb2 genes in the black rockfish, which have a regulatory role in the preparation for fertilization and hatching. This research provides a novel view of viviparity adaption and lays the groundwork for future research into vascular regulation of ovarian in the breeding cycle in black rockfish.