Piwi1 is essential for gametogenesis in mollusk Chlamys farreri.

Xiaoshi Ma,Zhifeng Zhang,Yuhan Wang,Zhenkui Qin,Dandan Yang,Shaoshuai Liang,Aichang Ji

doi:10.7717/peerj.3412

Abstract

Piwi (P-element induced wimpy testis) is an important gene involved in stem cell maintenance and gametogenesis in vertebrates. However, in most invertebrates, especially mollusks, the function of Piwi during gametogenesis remains largely unclear. To further understand the function of Piwi during gametogenesis, full-length cDNA of Piwi1 from scallop Chlamys farreri (Cf-Piwi1) was characterized, which consisted of a 2,637 bp open reading frame encoding an 878-amino acid protein. Cf-Piwi1 mRNA was mainly localized in the spermatogonia, spermatocytes, oogonia, oocytes of early development and intra-gonadal somatic cells. Additionally, the knockdown of Cf-Piwi1 by injection of Cf-Piwi1-dsRNA (double-stranded RNA) into scallop adductor led to a loss of germ cells in C. farreri gonads. Apoptosis was observed mainly in spermatocytes and oocytes of early development, as well as in a small number of spermatogonia and oogonia. Our findings indicate that Cf-Piwi1 is essential for gametogenesis in the scallop C. farreri.

Highlights

Gametogenesis is the basis of animal reproduction and mainly includes germ stem cell self-renewal, meiosis and maturation of gametes
No significant differences in Cf-Piwi1 expression levels were observed between the ovary and testis at the same developmental stages (P > 0.05)
In the planarian Schmidtea mediterranea, Piwi mRNA is visible in somatic stem cells and germ cells (GCs) (Reddien et al, 2005; Rossi et al, 2006; Palakodeti et al, 2008)

Summary

Introduction

Gametogenesis is the basis of animal reproduction and mainly includes germ stem cell self-renewal, meiosis and maturation of gametes. Studies of gametogenesis will help improve the reproductive ability and preservation of economically important species. It is known that many genes are involved in this process for model organisms, but the roles of these genes remain largely unknown in non-model organisms. Piwi (P-element induced wimpy testis), a PIWI subfamily member of the Argonaute superfamily, is identified based on two conserved domains, PAZ and PIWI (Cerutti, Mian & Bateman, 2000). The PAZ domain, at the center of the amino acid sequence, contains a typical single stranded nucleic acid binding motif that can bind to the 3 end of short RNA (Lingel et al, 2003; Yan et al, 2003). The PIWI domain, found in the C-terminal region, functions to maintain Piwi’s stability and is structurally similar to the RNase H catalytic domain (Liu et al, 2004; Song et al, 2004)

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