Sequence Conservation and Sexually Dimorphic Expression of the Ftz-F1 Gene in the Crustacean Daphnia magna

• Published in: PloS one 2016-05, Vol.11 (5), p.e0154636-e0154636
• Main Authors: Mohamad Ishak, Nur Syafiqah, Kato, Yasuhiko, Matsuura, Tomoaki, Watanabe, Hajime
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Base Sequence; Binding; Biological evolution; Biology and Life Sciences; Biotechnology; Cladocera; Cloning; Conservation; Conserved Sequence; Crustaceans; Daphnia; Daphnia - embryology; Daphnia - genetics; Daphnia - physiology; Daphnia magna; Daphniidae; Deoxyribonucleic acid; Dimorphism (Biology); DNA; DNA, Complementary - genetics; Drosophila; Drosophila melanogaster; Embryos; Engineering schools; Environmental effects; Evolutionary biology; Evolutionary genetics; Experiments; Females; Freshwater; FTZ-F1 gene; Gastrulation; Gene expression; Gene Expression Regulation, Developmental; Genes; Genetic aspects; Genomics; Homology; Insects; Isoforms; Ligands; Male; Males; Ovulation; Phylogeny; Physiological aspects; Population density; Proteins; Research and Analysis Methods; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA-mediated interference; Sex; Sex Characteristics; Sex determination; Sex differences; Sexual dimorphism; Splicing; Transcription Factors - chemistry; Transcription Factors - genetics
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0154636

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.