title: Molecular characterization and functional divergence of two Gadd45g homologs in sex determination in half-smooth tongue sole (Cynoglossus semilaevis).
abstract: The growth arrest and DNA-damage-inducible protein 45 gamma (Gadd45g) is known to play a major role in embryonic development and sex determination. In this study, two Gadd45g genes were isolated from half-smooth tongue sole (Cynoglossus semilaevis). Using chromosomal fluorescence in situ hybridization (FISH), Gadd45g1 and Gadd45g2 were located on the W and Z chromosomes, respectively. The full-length cDNA sequences of Gadd45g1 (1270bp) and Gadd45g2 (1181bp) were predicted to contain a 480-bp coding sequence that could encode a protein of 159 amino acids residues. A phylogenetic tree showed that the predicted Gadd45g1 and Gadd45g2 amino acid sequences clustered closely in one branch. It is proposed that Gadd45g1 and Gadd45g2 are paralogous genes derived from the divergence of the sex chromosome. Ka/Ks ratios indicated that Gadd45g1 and Gadd45g2 may have undergone a high number of mutations and have a divergence time of only about 68,000years, although Gadd45g homologs are highly conserved. The qRT-PCR demonstrated that Gadd45g1 and Gadd45g2 were highly expressed in ovary, and negligibly expressed in testis of male and neo-male. During development of the ovary (from 80 to 150days), the expression levels of both genes reached high levels. Gadd45g1 was also highly expressed at 50days, the stage just before gonad differentiation in C. semilaevis. All these findings imply functional divergence of the two Gadd45g homologs; Gadd45g1 may be necessary for sex differentiation in the early stage of gonad development, and then Gadd45g1 and Gadd45g2 maintain ovary development and the female character of half-smooth tongue sole.
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China; Fisheries College, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.
authors.forename: Wan-Jun
authors.initials: WJ
authors.lastname: Liu
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Li-Yan
authors.initials: LY
authors.lastname: Zhang
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Chang-Wei
authors.initials: CW
authors.lastname: Shao
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Na
authors.initials: N
authors.lastname: Wang
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Fisheries College, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.
authors.forename: Hai-Shen
authors.initials: HS
authors.lastname: Wen
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Fisheries College, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.
authors.forename: Zhong-Dian
authors.initials: ZD
authors.lastname: Dong
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Zhang
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Qingdao 266071, China. Electronic address: chensl@ysfri.ac.cn.
authors.forename: Song-Lin
authors.initials: SL
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D005260:Female; D005412:Flatfishes / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010053:Ovary / Q000378:metabolism; D010802:Phylogeny; D019849:Sex Determination Processes; D012733:Sex Differentiation; D013737:Testis / Q000378:metabolism; D000097642:GADD45 Proteins
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D000097642:GADD45 Proteins
keywords: Cynoglossus semilaevis; Gadd45g; Sex differentiation