Molecular characterization and expression pattern of three zona pellucida 3 genes in the Chinese sturgeon, Acipenser sinensis.

Chinese sturgeon (Acipenser sinensis) is a rare and endangered species and also an important resource for the sturgeon aquaculture industry. SMART cDNAs were synthesized from the ovary of A. sinensis, and the full-length cDNAs of three zona pellucida glycoprotein 3 genes (the new gene named AsZP3) were cloned and sequenced. AsZP3.1, AsZP3.2, and AsZP3.3 were 1,388 base pairs (bp), 1,288, and 1,290 bp in length, respectively, and they could be translated into proteins with 440, 394, and 398 amino acids, respectively. High level of amino acids sequence identity was seen between AsZP3.2 and AsZP3.3 (about 82%), but they share low identity with AsZP3.1 (26 and 23%, respectively). The AsZP3.1 has 42-50% amino acids sequence identity values with other fish and lower values with higher vertebrates (38%); AsZP3.2 and AsZP3.3 shared about 30-44% sequence identity with higher vertebrates and other fish. RT-PCR analysis indicated that AsZP3.1 displayed a wide tissue distribution at the mRNA levels including liver, kidney, spleen, heart, and ovary, but AsZP3.2 and AsZP3.3 mRNAs were expressed exclusively in the gonad. All three AsZP3 mRNAs were not detected during embryogenesis and early larval development; furthermore, they were not detected in the gonads of 1- and 2-year-old Chinese sturgeons. All three AsZP3 mRNAs were detected in the testes of 3-year-old males and in the ovaries of 4- and 5-year-old female Chinese sturgeons.