Molecular Characterization of a cDNA Encoding Putative Vitellogenin from the Pacific Oyster Crassostrea gigas

Abstract

To elucidate the molecular mechanisms involved in oogenesis, we applied a differential display method to identify genes whose expression was detected only in ovaries containing oocytes. One of the cDNA fragments isolated by mRNA differential display was similar in structure to vitellogenin. Using this fragment, a full-length cDNA encoding putative vitellogenin in the Pacific oyster Crassostrea gigas was cloned by RACE (rapid amplification of cDNA ends), and its amino acid sequence was deduced. The open reading frame predicted 1583 amino acid residues. The deduced primary structure of putative vitellogenin in C. gigas was shown to be similar to vitellogenins of various other mollusk, fish, crustacean and nematode species, especially in the N-terminal region. Reverse transcription-mediated PCR revealed that mRNA encoding putative vitellogenin was expressed only in the ovary. In situ hybridization analysis revealed that putative vitellogenin mRNA was expressed strongly in the follicle cells in the ovary. It is concluded that the follicle cells are the site of putative vitellogenin synthesis.

Interspecies comparison of selected pollution biomarkers in dreissenid spp. inhabiting pristine and moderately polluted sites

“…In mature females, Vtg are generally synthesized in response to endogenous estrogens, such as 17ß-estradiol (E2), released into the bloodstream and then stored in developing oocytes. Studies have outlined that levels of E2 in molluscs display a seasonal alternation associated with the reproductive cycle and are synchronized with variations of oocyte diameter and assumed Vitellogenin mRNA levels from early vitellogenic stage to spawning stage (Matsumoto et al, 1997(Matsumoto et al, , 2003Osada et al, 2004;Ni et al, 2014). Ni et al (2014) in their study recorded several magnitude higher vitellogenins expression in the ovary of C. gigas in the maturation and ripeness stages than in the partially spent stage.…”

Immunohistochemical observations of vitellin synthesis and accumulation processes in ovary of Ezo abalone Haliotis discus hannai

“…The Vn is synthesized as a precursor molecule, vitellogenin (Vtg), and processed by proteases into a mature molecule. The Vtg cDNAs have been clarified in C. gigas [7], P. yessoensis [8], blue mussel Mytilus edulis [9], H. discus hannai [10], and in some other mollusks. The amino acid sequences deduced from the cDNAs share 20 to 30 % similarity with Vtg of fish, nematodes, and crustaceans mainly in their N-terminal sequences [7,10].…”

“…The Vtg cDNAs have been clarified in C. gigas [7], P. yessoensis [8], blue mussel Mytilus edulis [9], H. discus hannai [10], and in some other mollusks. The amino acid sequences deduced from the cDNAs share 20 to 30 % similarity with Vtg of fish, nematodes, and crustaceans mainly in their N-terminal sequences [7,10]. Information on molluscan Vtg and Vn obtained from these studies is useful to monitor ovarian growth of the above mentioned species in the wild and under aquaculture conditions [2,5,11], and to evaluate the effects of environmental pollutants on reproductive activities of marine and freshwater mollusks [5,12,13].…”

“…Ovarian follicle cells are distributed within the germinal epithelium lining genital tubule or ovarian cavity, and are often observed located around the stalk of oocytes [7,16]. Vn synthesis has previously been supposed to occur in oocytes in C. gigas and P.…”

“…yessoensis [1,3], but analysis of the Vtg gene expression by in situ hybridization has clarified it to occur in the ovarian follicle cells in C. gigas [7] and H. discus hannai [10], or auxiliary cells (equivalent to the ovarian follicle cells) in P. yessoensis [8].…”