Identification and Functional Analysis of Glutathione S-Transferases from Sitophilus zeamais in Olfactory Organ

SIMPLE SUMMARY: Sitophilus zeamais is a worldwide pest that destroys many grain products, causing a loss of cereal quality and quantity resulting from its metabolites and behavior. Glutathione S-transferases (GSTs), as a group of odorant-degrading enzymes (ODEs), play an important role in degrading xenobiotic odorant molecules in insect olfactory sensing systems. However, there have been few reports about the function of the GST genes of S. zeamais in the odorant-degrading process. In this study, we characterized 13 full-length genes encoding GST sequences from S. zeamais and analyzed the expression pattern in different tissues of SzeaGSTd1. In addition, we investigated the ability of recombinant SzeaGSTd1 to degrade the volatile molecules of the host, and the data indicated that the content of capryl alcohol significantly decreased in the system. In summary, we believe SzeaGSTd1 plays a key role in the olfactory sensing system of S. zeamais. ABSTRACT: Odorant-degrading enzymes (ODEs) play an important role in rapidly degrading and inactivating odorant molecules that have completed information transmission, as well as in maintaining the stability and sensitivity of insect olfactory sensing systems. Glutathione S-transferases (GSTs), as a group of ODEs, supposedly bear the ability to catalyze the conjugation of glutathione (GSH) and xenobiotic odorant molecules in the degrading process. However, there are few reports regarding the role of the GST genes of Sitophilus zeamais in the degrading process. Thus, we characterized 13 full-length genes encoding GST sequences from S. zeamais, of which only SzeaGSTd1 contained a high abundance in the antennae. Ligand-binding assays implied that SzeaGSTd1 was able to catalyze the conjugation of GSH with 2, 4-dinitrochlorobenzene (CDNB). We investigated whether recombinant SzeaGSTd1 bears the ability to degrade the volatile molecules of the host; among the host volatiles, and found capryl alcohol to be a suitable substrate for SzeaGSTd1. These results strongly suggest that SzeaGSTd1 probably plays a role in auxiliary host location by degrading the host volatiles of capryl alcohol and exhibits a potential biological function in the olfactory sensing system of S. zeamais. Knowledge of the potential functions of SzeaGSTd1 will provide new ideas for biological control strategies for S. zeamais.