Molecular characterization and expression analysis of SYCP1 and SYCP3 in hybrid fish derived from Megalobrama amblycephala × Culter alburnus

Abstract

SYCP1 and SYCP3 are essential testis-specific genes for centromere pairing during meiosis, as well as for spermatogenesis and fertility in male germ cells. However, it is still unclear regarding the expression patterns in the fertile reciprocal hybrid offspring of Megalobrama amblycephala (blunt snout bream, BSB, 2n = 48) × Culter alburnus (topmouth culter, TC, 2n = 48). This research elucidated the genetic and expression characteristics of SYCP1 and SYCP3 through molecular cloning, sequence alignment, Western blotting, and immunohistochemistry to assess their roles in both hybrids and parents. The findings revealed that SYCP1 and SYCP3 exhibited high homology between M. amblycephala and C. alburnus, with varying degrees of chimerism in the BT and TB hybrids. The expression level of SYCP1 in these hybrids was intermediate between parents, while SYCP3 was more similar to M. amblycephala and significantly different from C. alburnus (p < 0.05). Western blotting confirmed the normal expression of both SYCP1 and SYCP3 proteins in the hybrid offspring. Immunohistochemistry verified the significant presence of these proteins in the testes of mature hybrids. These findings suggested that BT and TB hybrids retained the stability of the SYCP1 and SYCP3 genes inherited from their heterozygous parental origins, supporting independent protein expression despite slight variations in the CDS structure. Our results demonstrate that the normal expression of key meiotic genes plays an important role in overcoming reproductive barriers in distant hybridization, which is of great significance for genetic breeding in fish.