Three chemosensory proteins from the rice leaf folder Cnaphalocrocis medinalis involved in host volatile and sex pheromone reception

Authors: ZENG, FANG-FANG - Huazhong Agricultural University; LIU, HAO - Huazhong Agricultural University; SUN, SHUANG-FENG - Huazhong Agricultural University; Zhang, Aijun; LU, ZHONG-XIAN - Zhejiang Academy Of Agricultural Sciences; WANG, MAN-QUN - Huazhong Agricultural University

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2018
Publication Date: 5/26/2018
Citation: Zeng, F., Liu, H., Sun, S., Zhang, A., Lu, Z., Wang, M. 2018. Three chemosensory proteins from the rice leaf folder Cnaphalocrocis medinalis involved in host volatile and sex pheromone reception. Insect Biochemistry and Molecular Biology. https://doi.org/10.1111/imb.12503.
DOI: https://doi.org/10.1111/imb.12503

Interpretive Summary: Chemosensory proteins (CSPs) are a kind of small proteins that have recently been discovered in insect chemical communication systems, but their specific functions are still not clear. In this study, the rice leaf-folder (RLF), a serious insect pest for rice production, was chosen as a template insect to evaluate whether the three CSPs previously identified in RLF have olfactory function. By using different laboratory techniques, we demonstrated that two CSPs were involved in host plant recognition, while another CSP was involved in the process of mate selection. This research provides solid evidence for the involvement of CSPs in RLF chemical communication, which will help scientists and growers better understand the olfactory system employed by RLF for host selection and mate location. Therefore, it will enable the development of olfaction-based insect population detection tools for timely diagnosis and intervention of RLF infestation and to prevent RLF outbreaks in rice cultivation.

Technical Abstract: Chemosensory protein (CSP) is a kind of protein that has been considered to be an information carrier in insect chemoreception, capturing and transporting hydrophobic semiochemicals from air to olfactory receptors in the lymph of antennal chemosensilla. However, its specific functional role in insect chemoreception has not been fully elucidated. In this study, we have focused on the olfactory function analysis of three CSP genes (CmedCSP1-3) in the rice leaf folder Cnaphalocrocis medinalis (Guenee), which have been discovered by screening the antennal cDNA library in our previous study. Three CSP proteins were expressed and purified in bacterial expression system and the binding affinities of tested chemicals to all three CSPs (CmedCSP1-3) were measured using fluorescent binding assays. RNA interference was conducted by injecting dsRNA and then the antennal activities of host-related semiochemicals for host location and sex pheromone compounds for mate selection behaviors of C. medinalis were investigated using electroantennogram (EAG). Our results showed that the CmedCSP1-2 had high binding affinities with wide range of tested host-related semiochemicals, and their anti-bodies were mainly labeled in the sensilla basiconica, suggesting that the CSP1 and CSP2 were involved in the host plant recognition. By contrast, the CmedCSP3 demonstrated very limited binding affinities to above tested compounds. It exhibited better and preferential binding abilities to two sex pheromone components, Z11-16:Ac and Z11-16:Al, and highly labeled in the pheromone-sensitive sensilla trichodea and general odorant-sensitive sensilla basiconica, indicating that the CmedCSP3 was in the process of mate selection. In addition, the one-site mutants of CmedCSP2 binding assays also revealed that the binding affinities between amino acids and ligands were contributed not only by one amino acid site but also by the spatial structure of the protein. Moreover, deletion of C-terminal of the CSPs would cause the protein to lose almost all binding affinities. Together with the EAG recording data of compounds affected by RNA interference, our results have provided solid evidence for CSPs involvement in chemoreception of C. medinalis.