Identification of Vitellogenin 1 Potentially Related to Reproduction in the Cephalopod, Sepiella japonica

Vitellogenin (Vg) is the precursor of yolk protein, which plays an important role in the reproduction and development of oviparous animals. In this study, vitellogenin1 (Vg1) from Sepiella japonica was cloned and characterized, and its potential function in ovarian development was investigated. The full-length cDNAs of Vg1 was 5853 base pair (bp) that encoded 748 amino acids. Sequence analysis revealed that the overall protein sequence of Vg1 shared 66% identity with that of Uroteuthis edulis. Analyses with quantitative reverse transcription polymerase chain reaction (RT-qPCR) showed that the highest expression of Vg1 occurred in the ovary. As ovary developed, the expression of Vg1 increased in both ovary and liver from oogonia phase (I) to interstitial growth phase (III), and reached to the peak value at stage III. In addition, we examined the effects of Gonadotropin-releasing hormone (GnRH) on Vg1 expression in the ovary and liver were examined. The data showed that GnRH increased mRNA expression of Vg1, indicating that exogenous GnRH initially affected Vg1 expression and then influenced ovarian maturation. This study suggests that Vg1 might be involved in ovarian development in cephalopods.