Identification and comparative analysis of accessory gland proteins in Orthoptera

Accessory reproductive gland proteins (Acps) in Drosophila evolve quickly and appear to play an important role in ensuring the fertilization success of males. Moreover, Acps are thought to be involved in establishing barriers to fertilization between closely related species. While accessory glands are known to occur in the males of many insect groups, the proteins that are passed on to females by males during mating have not been well characterized outside of Drosophila. To gain a better understanding of these proteins, we characterized ESTs from the accessory glands of two cricket species, Allonemobius fasciatus and Gryllus firmus. Using an expressed sequence tag (EST) approach, followed by bioinformatic and evolutionary analyses, we found that many proteins are secreted and, therefore, available for transfer to the female during mating. Further, we found that most ESTs are novel, showing little sequence similarity between taxa. Evolutionary analyses suggest that cricket proteins are subject to diversifying selection and indicate that Allonemobius is much less polymorphic than Gryllus. Despite rapid nucleotide sequence divergence, there appears to be functional conservation of protein classes among Drosophila and cricket taxa.