AUTHOR=Wang Yayu , Wang Xiaoqiang , Ge Jingyuan , Wang Guiling , Li Jiale 

TITLE=Identification and Functional Analysis of the Sex-Determiner Transformer-2 Homologue in the Freshwater Pearl Mussel, Hyriopsis cumingii

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.704548

DOI=10.3389/fphys.2021.704548

ISSN=1664-042X

ABSTRACT=<p><italic>Transformer-2 (Tra-2)</italic> is an upstream regulatory element of the sex regulation mechanism in insects and plays a critical role in sex formation. To understand the role of <italic>tra-2</italic> in <italic>Hyriopsis cumingii</italic>, the full-length <italic>Hctra-2</italic> (1867 bp) was obtained from the gonads, and sequence alignment with other species showed that HCTRA-2 protein had a highly conserved RRM domain. Phylogenetic analysis showed that the HCTRA-2 protein was a close relative to of the mollusks TRA-2 protein. The qRT-PCR of tissue-specific expression pattern showed that the <italic>Hctra-2</italic> was abundant in gonads, and the expression in testes was higher than that in ovaries (<italic>p</italic> &lt; 0.01). It suggests that <italic>Hctra-2</italic> may play a potential regulatory role in gonadal development of <italic>H. cumingii</italic>. In the early gonadal development, the <italic>Hctra-2</italic> expression was the highest on the third day after fertilization and increased slightly from 4 months to 5 months, which may be related to the embryonic sex determination and early gonadal development. <italic>In situ</italic> hybridization showed that <italic>Hctra-2</italic> mRNA signals were present in both male and female gonads. After silencing <italic>Hctra-2</italic> by RNAi, the expression levels of <italic>Hcfem-1b</italic> and <italic>Hcdmrt</italic> were changed. It is speculated that there may be a certain relationship between them, which plays an important role in the sex regulation of <italic>H. cumingii</italic>. Our research will help to deepen our understanding of the shellfish sex determination mechanisms.</p>