Silencing of Chemosensory Protein Gene NlugCSP8 by RNAi Induces Declining Behavioral Responses of Nilaparvata lugens

Abstract

Chemosensory proteins (CSPs) play imperative functions in chemical and biochemical signaling of insects, as they distinguish and transfer ecological chemical indications to a sensory system in order to initiate behavioral responses. The brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae), has emerged as the most destructive pest, causing serious damage to rice in extensive areas throughout Asia. Biotic characteristics like monophagy, dual wing forms, and annual long-distance migration imply a critical role of chemoreception in N. lugens. In this study, we cloned the full-length CSP8 gene from N. lugens. Protein sequence analysis indicated that NlugCSP8 shared high sequence resemblance with the CSPs of other insect family members and had the typical four-cysteine signature. Analysis of gene expression indicated that NlugCSP8 mRNA was specifically expressed in the wings of mated 3-day brachypterous females with a 175-fold difference compare to unmated 3-day brachypterous females. The NlugCSP8 mRNA was also highly expressed in the abdomen of unmated 5-day brachypterous males and correlated to the age, gender, adult wing form, and mating status. A competitive ligand-binding assay demonstrated that ligands with long chain carbon atoms, nerolidol, hexanal, and trans-2-hexenal were able to bind to NlugCSP8 in declining order of affinity. By using bioinformatics techniques, three-dimensional protein structure modeling and molecular docking, the binding sites of NlugCSP8 to the volatiles which had high binding affinity were predicted. In addition, behavioral experiments using the compounds displaying the high binding affinity for the NlugCSP8, revealed four compounds able to elicit significant behavioral responses from N. lugens. The in vivo functions of NlugCSP8 were further confirmed through the testing of RNAi and post-RNAi behavioral experiments. The results revealed that reduction in NlugCSP8 transcript abundance caused a decrease in behavioral response to representative attractants. An enhanced understanding of the NlugCSP8 is expected to contribute in the improvement of more effective and eco-friendly control strategies of BPH.

The role of chemosensory protein 10 in the detection of behaviorally active compounds in brown planthopper, Nilaparvata lugens

“…lugens to identify the defense responses of its host plant. In one of our previous studies, eicosane (Ki = 12.37 μ mol/L) moderately bound with NlugCSP8 (Waris et al ., ), while in this study, it exhibited relatively high binding affinity with NlugCSP10 (Ki = 4.36 μ mol/L). In addition, we confirmed that the rice volatile 2‐tridecanone, which is known to attract the BPH (Obata et al ., ), and can stimulate ecdysone 20‐monooxygenase activity in Spodoptera frugiperda (Yu, ) and retard the development of Helicoverpa armigera (Zhang et al ., ), also exhibited relatively moderate binding affinity to NlugCSP10 (Ki = 6.34 μ mol/L).…”

“…The specificity of each primer set was authenticated by the melt‐curve, in which there was only one single gene‐specific peak, and the linear standard curve was used to calculate the amplification efficiency (E‐value) by the equation E = 10 −1/slope . The qRT‐PCR reaction was conducted in 20 μ L mixture containing 10 μ L SYBR Green PCR Master Mix, 1 μ L cDNA template, 0.5 μ L of each primer (1 μ mol/L) and 8 μ L sterilized ultrapure water using the following qRT‐PCR conditions; one cycle of 95 °C for 3 min, followed by 40 cycles of 95 °C for 10 s and 57 °C for 30 s. β ‐actin (GenBank accession number: EU179846) was used as a reference gene to calculate the relative expression levels (Zhou et al ., ; Waris et al ., ). The data were analyzed using the method (Livak & Schmittgen, ).…”

A Chemosensory Protein BtabCSP11 Mediates Reproduction in Bemisia tabaci

“… Kulmuni and Havukainen (2013) showed that 5-helical CSPs are the only highly conserved CSPs in Arthropoda and are likely involved in functions other than chemosensation, whereas the vastly divergent 6-helical CSPs carry out solely chemosensory functions. Evidence strongly suggests that CSPs might be involved in chemodetection, as are OBPs ( Waris et al, 2018 , 2020b ). In the honeybee, CSP3 specifically binds some components of brood pheromone ( Briand et al, 2002 ).…”

NlATG1 Gene Participates in Regulating Autophagy and Fission of Mitochondria in the Brown Planthopper, Nilaparvata lugens

“…For example, piercing-sucking insects feed on phloem sap while ingesting very little plant tissue, so foliar application of dsRNA by spraying is not likely to trigger an effective RNAi response in them. Microinjection is an effective strategy for delivering dsRNA into many orders of insects, including BPH Zhu et al, 2017;Waris et al, 2018;Ge et al, 2019), but this approach is not a feasible strategy for achieving widespread crop protection in the field (Huvenne and Smagghe, 2010;Scott et al, 2013;Liu et al, 2019). Recently, Li et al (2015) suggested that soaking the root system in dsRNA could be used as a dsRNA-delivery strategy during crop irrigation, which is also suitable for BPH control.…”