Molecular characterization of the cDNAs of two zona pellucida genes in the Chinese sturgeon, Acipenser sinensis Gray, 1835

The Chinese sturgeon, Acipenser sinensis, is a large-sized panadromous cartilagous fish and requires more than ten years to reach sexual maturity. An understanding of the reproductive organs and fertilization process is a precondition for controlled reproduction of this endangered species. The developing oocyte is surrounded by an extracellular matrix composed of the zona pellucide (ZP) protein in several isoforms, all of which play important roles in fertilization and embryo protection. The present study reports the identification of two ZP genes, AsZPAX and AsZPB, in this fish. The full-length cDNAs of AsZPAX and AsZPB were 2950 base pairs (bp) and 1832bp, predicting proteins of 946 and 592 amino acid residues, respectively. Both proteins have a conserved ZP domain. In a gene tree, AsZPAX and AsZPB were respectively clustered with their counterparts in other vertebrates. Tissue distribution analysis demonstrated that the AsZPAX RNA was transcribed in both the ovary and the liver, while AsZPB was transcribed exclusively in the ovary. RNA in situ hybridization revealed apparent RNA expression of both AsZPAX and AsZPB in growing oocytes of the 4-year-old ovary