Seminal fluid proteins in the Queensland fruit fly: Tissue origins, effects of mating and comparative genomics

In many insect species, the ability of males to inhibit their mates from remating is an important component of fitness. This ability is also essential for the effective management of insect pests, including tephritid fruit flies, using the Sterile Insect Technique. Here we apply transcriptomics and proteomics to male reproductive tissues before and after mating to characterize components of semen that might mediate remating inhibition in Queensland fruit fly. We found 144 genes whose transcripts were enriched, or proteins expressed, in reproductive tissue and which also varied in amount after mating. Some were associated with testes, accessory glands and ejaculatory apodeme, but those from the ejaculatory apodeme were over-represented compared to those not enriched in reproductive tissue or mating responsive. These included 13 related genes clustered within one Mb on chromosome 5. Functional annotations implicated a broad range of biochemical processes in the genes/proteins enriched in reproductive tissue and mating responsive, with cuticle structure most commonly implicated among the subset of these that were apodeme-enriched and a kinase involved in vitellogenesis implicated for one of the 13 clustered genes. We did not find a homolog of the much studied Drosophila melanogaster Sex Peptide but comparative genomics indicated that some of the tissue-enriched, mating responsive genes/proteins were rapidly evolving in tephritids (including in the Queensland fruit fly lineage), suggesting recent adaptation to new functional niches. Our results provide a set of candidate mediators of remating inhibition for further functional testing.