Mating-responsive genes from the testes and male accessory glands of the Mediterranean fruit fly, Ceratitis capitata

Insect seminal fluid is a complex blend of spermatozoa, proteins, carbohydrates and lipids, which are produced in the male reproductive tract. This mixture is transferred during copulation and induces post-mating responses in the female. Molecular characterization of the protein components of seminal fluid in the Mediterranean fruit fly (medfly), Ceratitis capitata, is limited, even though different studies suggest that some of these proteins are biologically active. We report the functional annotation of 8448 expressed sequence tags (ESTs) derived from the testes and male accessory glands, to identify transcripts encoding putative secreted peptides that might elicit post-mating responses in females. The ESTs were assembled into 3344 contigs, of which over 33% produced no hits against the nr database, putatively representing novel medfly sequences. Extraction of the coding sequences resulted in a total of 3371 peptides. Four hundred peptides were found to have putative secretory activity, including odorant binding proteins, protease inhibitor domain-containing peptides, antigen 5 proteins, mucins, and immunity-related sequences. Quantitative RT-PCR on transcripts expressed in the accessory glands revealed that several changed in abundance after one or more copulations, compared to virgin males of the same age. Our results suggest the presence of transcriptional switch points possibly related to the need to replenish transcripts encoding secreted proteins with an active role in the seminal fluid. This represents the first large-scale dataset for novel studies on functions and processes associated with the reproductive biology of this invasive pest species. The identified genes may help the study of the evolution of the genome, in the light of its high adaptive potential. In addition, studies of male recovery dynamics in terms of accessory glands gene expression profiles and correlated remating inhibition mechanisms will permit the improvement of the current pest management approaches.