Oocytes express an endogenous red fluorescent protein in a stony coral, Euphyllia ancora: a potential involvement in coral oogenesis.

Shinya Shikina,Yi-Ling Chiu,Yan-Horn Lee,Chieh-Jhen Chen,Ching-Fong Chang,Yi-Jou Chung

doi:10.1038/srep25868

Abstract

To date,the molecular and cellular mechanisms underlying coral sexual reproduction remain largely unknown. We then performed a differential screen to identify genes related to oogenesis in the stony coral Euphyllia ancora. We identified a clone encoding a novel red fluorescent protein cDNA of E. ancora (named EaRFP). Microscopic observation and quantitative RT-PCR revealed that EaRFP is almost exclusively expressed in the ovary of the adult coral. The combination of the ovarian-cell separation method and the RT-PCR analysis revealed that the oocytes, but not the ovarian somatic cells, are the cells expressing EaRFP. Immunohistochemical analysis revealed that the expression of EaRFP starts in the early stage of the oocyte and continues until the maturation period. Furthermore, recombinant EaRFP was shown to possess an H2O2 degradation activity. These results raise the possibility that EaRFP plays a role in protecting the oocytes from oxidative stress from the early to late stages of oogenesis. The present study provides not only the first evidence for the potential involvement of FPs in coral oogenesis but also an insight into a cellular strategy underlying coral sexual reproduction.

Highlights

Dozens of spermatogonia surrounded by a thin layer of mesoglea
Quantitative reverse transcription (RT)-PCR analysis revealed that the expression levels of a clone #2-6, which was identified by the screening of Suppression subtractive hybridization (SSH) cDNA library, were significantly up-regulated during the female reproductive period (April, 2011) compared to the non-reproductive period (June, 2010) in the female reproductive tissues which encompass the ovary (Fig. 1a)
The full-length cDNA was 1,079 bp in length and contained an open reading frame (ORF) of 678 bp corresponding to 226 amino acid residues, a 5′untranslated region (UTR) of 85 bp, and a 3′UTR of 321 bp including a poly A tail

Summary

Introduction

Dozens of spermatogonia surrounded by a thin layer of mesoglea. Spermatogonial proliferation, meiotic differentiation, and spermiogenesis take place within each spermary[3,6,7]. We reported a study describing the SSH-based identification and characterization of a novel yolk protein cDNA, named euphy, in a gonochoric stony coral, Euphyllia ancora[15]. Through the course of our SSH screening to explore oogenesis-related genes, we identified several clones that were up-regulated during the reproductive period of the female E. ancora. The biological relationship between fluorescent proteins (FPs) and oogenesis has been relatively unexplored in corals, this prompted us to perform the further characterization of the clone. We present the molecular identification and functional characterization of a novel red fluorescent protein that is endogenously, and almost exclusively, expressed in the oocytes from an early stage of oogenesis in the adult E. ancora

Methods

Results

Conclusion