Transcribed sex-specific markers on the Y chromosome of the oriental fruit fly, Bactrocera dorsalis

Abstract

AbstractBackgroundThe Oriental fruit fly,Bactrocera dorsalis, is a highly polyphagous invasive species with a high reproductive potential. In many tropical and subtropical parts of the world it ranks as one of the major pests of fruits and vegetables. Due to its economic importance, genetic, cytogenetic, genomic and biotechnological approaches have been applied to understand its biology and to implement the Sterile Insect Technique, currently a part of area-wide control programmes against this fly. Its chromosome complement includes five pairs of autosomes and the sex chromosomes. The X and Y sex chromosomes are heteromorphic and the highly heterochromatic and degenerate Y harbours the male factorBdMoY. The characterization of the Y chromosome in this fly apart from elucidating its role as primary sex determination system, it is also of crucial importance to understand its role in male biology. The repetitive nature of the Y chromosome makes it challenging to sequence and characterise.ResultsUsing Representational Difference Analysis, fluorescent in situ hybridisation on mitotic chromosomes and in silico genome resources, we show that theB. dorsalisY chromosome harbours transcribed sequences ofgyf,(typo-gyf) a homologue of theDrosophila melanogaster Gigyfgene, and of a non-LTR retrotransposon R1. Similar sequences are also transcribed on the X chromosome. Paralogues of theGigyfgene are also present on the Y and X chromosomes of the related speciesB. tryoni. Another identified Y-specific repetitive sequence linked toBdMoYappears to be specific toB. dorsalis.ConclusionsOur random scan of the Y chromosome provides a broad picture of its general composition and represents a starting point for further applicative and evolutionary studies. The identified repetitive sequences can provide a useful Y-marking system for molecular karyotyping of single embryos. Having a robust diagnostic marker associated withBdMoYwill facilitate studies on howBdMoYregulates the male sex determination cascade during the embryonic sex-determination window. The Y chromosome, despite its high degeneracy and heterochromatic nature, harbours transcribed sequences oftypo-gyfthat may maintain their important function in post-transcriptional mRNA regulation. That transcribed paralogous copies ofGigyfare present also on the X and that this genomic distribution is maintained also inB. tryoniraises questions on the evolution of sex chromosomes inBactroceraand other tephritids.