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Title: Interactions of two odorant-binding proteins from Cnaphalocrocis medinalis Güenée (Lepidoptera: Pyralidae)

item SUN, XIAO - Huazhong Agricultural University
item ZENG, FANG-FANG - Huazhong Agricultural University
item YAN, MIAO-JUN - Huazhong Agricultural University
item Zhang, Aijun
item WANG, MAN-QUN - Huazhong Agricultural University

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2016
Publication Date: 8/9/2016
Citation: Sun, X., Zeng, F., Yan, M., Zhang, A., Wang, M. 2016. Interactions of two odorant-binding proteins from Cnaphalocrocis medinalis Güenée (Lepidoptera: Pyralidae). Insect Molecular Biology. 25(6):712-723.

Interpretive Summary: Rice is an extremely important agricultural commodity that is consumed by humans worldwide. Besides adverse weather, insect pest epidemics are the major limiting factor in rice cultivation, often resulting in considerable yield loss. Among the pests attacking rice, the leaffolder causes major damage in all rice producing environments worldwide. Insecticide application in early season has little or no economic return for leaffolder control. Instead, it can actually cause ecological disruptions in natural biological control processes and enhance the development of secondary pests. For these reasons, alternative management tools are urgently needed to control leaffolder infestation. The adult leaffolders utilize their sensitive olfactory system to find food and locate mates from a distance by detecting volatile odorants emitted from these sources. Therefore, study of this olfactory system to regulate the reception of these odorant signals may result in a safe and effective method for management of this pest. In this study, three odorant-binding proteins (OBPs) were identified from the leaffolder antennae, which were proposed to participate in olfactory detection of rice plants. The interactions among different OBPs within the same insect antennal sensilla during the perception of rice plant volatiles were also well demonstrated by different molecular biological and electrophysiological approaches. The findings of this research will help to answer some fundamental questions about how an insect detects, encodes, and processes sensory stimuli. Understanding of the olfactory system involved in detection of these signals will help scientists and growers to develop olfaction based and environmentally benign insect infestation detection and control agents to prevent leaffolder outbreaks in rice cultivation.

Technical Abstract: It is well known that the odorant-binding proteins (OBPs) play important roles in insect olfactory systems. However, little attention has been paid to interactions among different OBPs within the same insect antennal sensilla. To explore the interactions of OBPs in olfactory coding in the rice leaffolder Cnaphalocrocis medinalis, ligand-binding experiment, molecular docking, and RNA interference and electrophysiological recording were performed. In this species, two OBPs, CmedOBP2 and CmedOBP3, are proposed to participate in rice plant olfactory detection. Therefore, ligand-binding characteristics were studied under single and binary OBP mixture conditions at different pH levels. The experimental results showed that the binding affinity of CmedOBP2 and CmedOBP3 exhibited a wide flexibility. It not only depends on the nature of the ligand and environment pH, but also on the levels of interaction between these two CmedOBPs. Such interaction in binding ligands could explain the reason why some of low-affinity compounds could elicit strong electroantennogram (EAG) responses in our previous studies. Also, the binding sites of CmedOBP2 and CmedOBP3 were well predicted by three-dimensional structure modeling and molecular docking experiments. In addition, the interaction of two OBPs, CmedOBP2 and CmedOBP3, in the perception of rice plant volatiles was further demonstrated by RNA interference experiment. When the single dsRNA-CmedOBP2 was injected into females, expression of CmedOBP3 was significantly knockdown, and vice versa. When both dsRNA-CmedOBP2 & 3 were injected, a higher reduction of the EAG responses was induced than that by single dsRNA injection.