title: Sequence Conservation and Sexually Dimorphic Expression of the Ftz-F1 Gene in the Crustacean Daphnia magna.
abstract: Identifying the genes required for environmental sex determination is important for understanding the evolution of diverse sex determination mechanisms in animals. Orthologs of Drosophila orphan receptor Fushi tarazu factor-1 (Ftz-F1) are known to function in genetic sex determination. In contrast, their roles in environmental sex determination remain unknown. In this study, we have cloned and characterized the Ftz-F1 ortholog in the branchiopod crustacean Daphnia magna, which produces males in response to environmental stimuli. Similar to that observed in Drosophila, D. magna Ftz-F1 (DapmaFtz-F1) produces two splicing variants, αFtz-F1 and βFtz-F1, which encode 699 and 777 amino acids, respectively. Both isoforms share a DNA-binding domain, a ligand-binding domain, and an AF-2 activation domain and differ only at the A/B domain. The phylogenetic position and genomic structure of DapmaFtz-F1 suggested that this gene has diverged from an ancestral gene common to branchiopod crustacean and insect Ftz-F1 genes. qRT-PCR showed that at the one cell and gastrulation stages, both DapmaFtz-F1 isoforms are two-fold more abundant in males than in females. In addition, in later stages, their sexual dimorphic expressions were maintained in spite of reduced expression. Time-lapse imaging of DapmaFtz-F1 RNAi embryos was performed in H2B-GFP expressing transgenic Daphnia, demonstrating that development of the RNAi embryos slowed down after the gastrulation stage and stopped at 30-48 h after ovulation. DapmaFtz-F1 shows high homology to insect Ftz-F1 orthologs based on its amino acid sequence and exon-intron organization. The sexually dimorphic expression of DapmaFtz-F1 suggests that it plays a role in environmental sex determination of D. magna.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Nur Syafiqah
authors.initials: NS
authors.lastname: Mohamad Ishak
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.|Frontier Research Base of Global Young Researchers, Graduate School of Engineering, Osaka University, Suita, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D003621:Daphnia / Q000196:embryology* / Q000235:genetics* / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D023281:Genomics; D008297:Male; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012727:Sex Characteristics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D014157:Transcription Factors