title: Expression patterns of sex-determination genes in single male and female embryos of two Bactrocera fruit fly species during early development.
abstract: In tephritids, the sex-determination pathway follows the sex-specific splicing of transformer (tra) mRNA, and the cooperation of tra and transformer-2 (tra-2) to effect the sex-specific splicing of doublesex (dsx), the genetic double-switch responsible for male or female somatic development. The Dominant Male Determiner (M) is the primary signal that controls this pathway. M, as yet uncharacterized, is Y-chromosome linked, expressed in the zygote and directly or indirectly diminishes active TRA protein in male embryos. Here we first demonstrated the high conservation of tra, tra-2 and dsx in two Australian tephritids, Bactrocera tryoni and Bactrocera jarvisi. We then used quantitative reverse transcription PCR on single, sexed embryos to examine expression of the key sex-determination genes during early embryogenesis. Individual embryos were sexed using molecular markers located on the B. jarvisi Y-chromosome that was also introgressed into a B. tryoni line. In B. jarvisi, sex-specific expression of tra transcripts occurred between 3 to 6 h after egg laying, and the dsx isoform was established by 7 h. These milestones were delayed in B. tryoni lines. The results provide a time frame for transcriptomic analyses to identify M and its direct targets, plus information on genes that may be targeted for the development of male-only lines for pest management.
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia.
authors.forename: J L
authors.initials: JL
authors.lastname: Morrow
authors.forename: M
authors.initials: M
authors.lastname: Riegler
authors.forename: M
authors.initials: M
authors.lastname: Frommer
authors.forename: D C A
authors.initials: DC
authors.lastname: Shearman
mesh_terms: D000818:Animals; D001315:Australia; D001483:Base Sequence; D004625:Embryo, Nonmammalian; D005260:Female; D015870:Gene Expression; D008297:Male; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019849:Sex Determination Processes / Q000235:genetics*; D033621:Tephritidae / Q000196:embryology / Q000235:genetics*
chemical_list: D012333:RNA, Messenger
keywords: Bactrocera; Dominant Male Determiner; quantitative reverse transcription PCR; sex-determination; single-embryo