title: The transformer genes in the fig wasp Ceratosolen solmsi provide new evidence for duplications independent of complementary sex determination.
abstract: Transformer (tra) is the key gene that turns on the sex-determination cascade in Drosophila melanogaster and in some other insects. The honeybee Apis mellifera has two duplicates of tra, one of which (complementary sex determiner, csd) is the primary signal for complementary sex-determination (CSD), regulating the other duplicate (feminizer). Two tra duplicates have been found in some other hymenopteran species, resulting in the assumption that a single ancestral duplication of tra took place in the Hymenoptera. Here, we searched for tra homologues and pseudogenes in the Hymenoptera, focusing on five newly published hymenopteran genomes. We found three tra copies in the fig wasp Ceratosolen solmsi. Further evolutionary and expression analyses also showed that the two duplicates (Csoltra-B and Csoltra-C) are under positive selection, and have female-specific expression, suggesting possible sex-related functions. Moreover, Aculeata species exhibit many pseudogenes generated by lineage-specific duplications. We conclude that phylogenetic reconstruction and pseudogene screening provide novel evidence supporting the hypothesis of independent duplications rather an ancestral origin of multiple tra paralogues in the Hymenoptera. The case of C. solmsi is the first example of a non-CSD species with duplicated tra, contrary to the previous assumption that derived tra paralogues function as the CSD locus.
authors.affiliation: Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: L-Y
authors.initials: LY
authors.lastname: Jia
authors.affiliation: Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: J-H
authors.initials: JH
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: T-L
authors.initials: TL
authors.lastname: Xiong
authors.affiliation: Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan, China.
authors.forename: L-M
authors.initials: LM
authors.lastname: Niu
authors.affiliation: Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.|Plant Protection College, Shandong Agricultural University, Tai'an, China.
authors.forename: D-W
authors.initials: DW
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D020440:Gene Duplication; D017344:Genes, Insect; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D011544:Pseudogenes; D012641:Selection, Genetic; D019849:Sex Determination Processes; D014863:Wasps / Q000235:genetics*
keywords: alternative splicing; complementary sex-determination; gene duplication; inbreeding; pseudogene