Two gustatory receptors are necessary for sensing sucrose in an egg parasitoid, Trichogramma chilonis

The gustatory system plays vital roles in food selection and feeding behaviours, as well as in other life activities in insects. In the process of taste perception, the functions of gustatory receptors are extremely important for insects. Trichogramma chilonis, a species of egg parasitoid, is often used as an effective biocontrol agent for agricultural and forestry pests. The utilization of T. chilonis has been well established, but the gustatory receptors, constituting the key factor in the molecular mechanism of gustation, are still unknown. In this study, we obtained two full-length cDNAs encoding putative sugar receptors (TchiGR64f1 and TchiGR64f2), and the qRT-PCR results showed that TchiGR64f1 and TchiGR64f2 were expressed from the larval to adult stages. The expression of TchiGR64f1 and TchiGR64f2 differed between male and female adults. Functional analysis of TchiGR64f1 and TchiGR64f2 was conducted based on the Xenopus oocyte expression system and the two-electrode voltage-clamp system. The electrophysiological results showed that the combination of TchiGR64f1?+?TchiGR64f2 was exclusively tuned to sucrose. Then, T. chilonis adults showed a preference for sucrose in a behavioural experiment. Additionally, sucrose consumption prolonged the lifespan and improved the fecundity of T. chilonis. These results not only enrich the reservoir of information on gustatory receptors in T. chilonis but also provide basic knowledge for further research on taste reception and for the development of a better strategy for the application of T. chilonis in biocontrol.