Molecular Cloning and Expression Profile of Sex-Specific Genes, Figla and Dmrt1, in the Protogynous Hermaphroditic Fish, Halichoeres Poecilopterus

Abstract

The genes folliculogenesis specific basic helix-loop-helix (facor in the germline alpha, Figla) and doublesex and mab-3 related transcription factor 1 (Dmrt1) are female- and male-specific genes that play key roles in sex differentiation. To obtain a better understanding of the molecular mechanisms underlying female-to-male sex change, we cloned the cDNAs of these genes from an ovary and a testis of the protogynus wrasse, Halichoeres poecilopterus. This fish has two isoforms of Dmrt1, Dmrt1a and Dmrt1b, caused by an alternative splicing. The Dmrt1b has an insertion of three nucleotides (CAG) in the open reading frame. Figla and Dmrt1 displayed gonadal-specific expression and abundant in the ovaries and in the testes, respectively. In particular, levels of Figla expression in the ovaries were higher in the spawning season than in the non-spawning season. Once sex change began, Figla mRNA decreased and Dmrt1 mRNA increased with progression of oocyte degeneration and spermatogenesis. These expression levels were maintained until the completion of the sex change. Low Figla and high Dmrt1 were also observed in testes of primary males, which functioned as a gonochoristic male throughout its life span in this wrasse. The results of this study suggest that these genes may regulate the gonadal transition from ovary to testis by the same mechanism as that of formation and maintenance of the primary testis in H. poecilopterus.

The transcriptomic signature of different sexes in two protogynous hermaphrodites: Insights into the molecular network underlying sex phenotype in fish

“…This transcription factor up-regulates ZP genes, which code for products used to build the vitelline envelope surrounding eggs in teleosts (zona matrix) 76 – 78 . Moreover, it has been suggested that the Figla factor displays an anti-parallel direction of expression to Dmrt1 during the transition from male to female in a protandrous 79 and vice versa in a protogynous teleosts 80 . The same expression pattern was showed for Foxl2 , a prominent marker of ovarian development across vertebrates 81 .…”

Sexual Fate Reprogramming in the Steroid-Induced Bi-Directional Sex Change in the Protogynous Orange-Spotted Grouper, Epinephelus coioides

“…In contrast to the rapid decreases in the male-related genes, our results demonstrate that the female-related genes ( figla , foxl2 , and cyp19a1a ) were gradually increased (but not rapidly) after AI/MT-termination. In fish, figla is a female marker expressed in the ovary [ 24 , 46 ]. In addition, black porgy figla /Figla existed only in oocytes, but not oogonia [ 47 ].…”

Bending Genders: The Biology of Natural Sex Change in Fish

“…In trying to understand the molecular control of sex change in sequential hermaphrodites, gene expression studies have focussed on these core genes and their potential proximate regulators. Most work has focussed on the protandrous black porgy [Wu and Chang, 2009;Wu et al, 2010aWu et al, , b, 2012Wu et al, , 2015 and on protogynous wrasse and grouper [Li et al, 2006;Xia et al, 2007;Alam et al, 2008;Liu et al, 2009;Kobayashi et al, 2010b;Miyake et al, 2012;Horiguchi et al, 2013;. Recently, and for the first time, whole-transcriptome expression analysis was used to comprehensively examine how expression landscapes alter across natural sex change in brain and gonad tissues of the protogynous bluehead wrasse [Liu, 2016].…”