A sex-specific homologue of waprin is essential for embryonic development in the red flour beetle, Tribolium castaneum

Waprin, a WAP (Whey acidic protein) domain-containing extracellular secretory protein, is widely known for its antibacterial properties. In this study, a waprin homologue (Tc_wap(F)) expressing in a female-specific manner was identified in Tribolium castaneum, through the analysis of sex-specific transcriptomes. Developmental- and tissue-specific profiling revealed the widespread expression of Tc_wap(F) in adult female tissues, particularly in the ovary, gut and fatbody. This female-specific expression of Tc_wap(F) is not regulated by the classical sex-determination cascade of T. castaneum, as we fail to get any attenuation in Tc_wap(F) transcript levels in Tcdsx and Tctra (key players of sex determination cascade of T. castaneum) knockdown females. RNA interference-mediated knockdown of Tc_wap(F) in females led to the non-hatching of eggs laid by these females, suggesting the crucial role of Tc_wap(F) in the embryonic development in T. castaneum. This is the first report on the identification of a sex-specific waprin homologue in an insect and its involvement in embryonic development. Future investigations on the functional conservation of insect waprins and their mechanistic role in embryonic development can be exploited for improving pest management strategies.