Expression pattern of Piwi-like gene implies the potential role in germline development in the Pacific oyster Crossosrea gigas

Abstract

Piwi is necessary for germ cell development in a diverse range of organisms and homologues have been commonly used to identify primordial germ cells (PGCs) during embryogenesis. Here, we isolated full-length cDNA of Piwi ortholog in the Pacific oyster Crassostrea gigas and characterized its expression patterns (Cg-Piwi-like) along with analyzing the expression alternation in the gonad of diploids compared with those sterile triploids. qPCR showed that the transcript of Cg-Piwi-like was mainly restricted to the gonad in diploids with ovarian tissues of triploids showing the highest expression. in situ hybridization revealed that Cg-Piwi-like was found in both female and male gonad where the strongest expression was shown in the germ cells at early stages with no signal in somatic cells. Whole-mount in situ hybridization suggested Cg-Piwi-like was maternally deposited and the localization of Cg-Piwi-like mRNA in mesodermal cells might be the putative PGCs in C. gigas. These results suggest that Cg-Piwi-like was involved in germ line formation, differentiation, and maintenance of germ cells in C. gigas. The obtained findings provide valuable evidences to further facilitate identification of the putative PGCs in the Pacific oyster using Cg-Piwi-like as a molecular marker.

Keywords

• Piwi
• Gonad development
• Primordial germ cell
• Molecular maker
• Crassostrea gigas