Candidate Chemosensory Genes Identified in the Adult Antennae of Sympiezomias velatus and Binding Property of Odorant-Binding Protein 15

Abstract

Chemosensory genes play important roles in insect behaviors and have thus become potential molecular targets for pest control based on the manipulation of chemoreception-driven behaviors. The great gray weevil Sympiezomias velatus (Chevrolat) (Coleoptera: Curculionidae) is an important agricultural pest that causes serious economic losses to many crops in China, but its chemosensory genes have not been reported. Here we assembled the antennal transcriptomes of female and male adult S. velatus and revealed the major chemosensory genes necessary for olfaction. A total of 138 candidate chemosensory genes in six families were identified, including 41 encoding odorant-binding proteins (OBPs), 11 encoding chemosensory proteins (CSPs), 62 encoding odorant receptors (ORs), 15 encoding gustatory receptors (GRs), six encoding ionotropic receptors (IRs), and three encoding sensory neuron membrane proteins (SNMPs). We analyzed their phylogenetic relationship based on the amino acid sequences of these chemosensory-related protein families in S. velatus and other insects, and the expression profiles based on their antennal transcriptomes. Chemosensory genes that show antenna-abundant/specific or sex-biased expression were observed, suggesting that these genes might have functions in olfaction. Furthermore, we chose an antenna-abundant OBP belonging to ABPX subfamily, SvelOBP15, to investigate its binding property. The results showed that among 33 tested compounds, SvelOBP15 displayed high binding affinities (Ki = 7.36–12.94 μmol/L) with farnesol, nerolidol, limonene and diisobutyl phthalate, indicating that SvelOBP15 plays olfactory roles by binding and transporting specific plant volatiles. These findings will help us better understand the olfactory systems of S. velatus, and provide a basis for functional elucidation of these chemosensory genes.

The Sequence Characteristics and Binding Properties of the Odorant-Binding Protein SvelOBP1 from Sympiezomias velatus (Coleoptera: Curculionidae) to Jujube Volatiles

“…SvelOBP1 was one of the most abundant OBPs in the transcript level of S. velatus. The expression level of OBPs is interrelated to their physiological functions [31]. Based on the expression patterns, the dominant body part expressing SvelOBP1 was the antennae and the expression of SvelOBP1 was higher in male antennae than that in female antennae.…”

“…These two ligands were both abundant plant volatiles with high binding affinities to insect OBPs [44,[46][47][48][49][50]. In Li's study [31], the binding affinity of SvelOBP15 with 33 plant volatiles was determined. The results showed that SvelOBP15 could bind with four plant volatiles, and it hardly bound with (Z)-hex-3-en-1-ol (K i > 16 µM).…”

“…OBPs are potential molecular targets for finding novel lures for pest control [30]. Although SvelOBP15 was identified and its binding affinities have been quantified [31], our knowledge of OBPs in S. velatus is still insufficient and more investigations are required. The fragments per kilobase of transcript per million mapped read (FPKM) values of SvelOBP1 were highest based on the transcriptome of S. velatus antennae (the sequence of SvelOBP1 in this study is consistent with SvelOBP37 in Li's study) [31].…”

“…Although SvelOBP15 was identified and its binding affinities have been quantified [31], our knowledge of OBPs in S. velatus is still insufficient and more investigations are required. The fragments per kilobase of transcript per million mapped read (FPKM) values of SvelOBP1 were highest based on the transcriptome of S. velatus antennae (the sequence of SvelOBP1 in this study is consistent with SvelOBP37 in Li's study) [31]. Based on this conclusion, we hypothesized that SvelOBP1 is an antennae-enriched OBP gene which is related to host plant recognition.…”

Antennal Transcriptome Evaluation and Analysis for Odorant-Binding Proteins, Chemosensory Proteins, and Suitable Reference Genes in the Leaf Beetle Pest Diorhabda rybakowi Weise (Coleoptera: Chrysomelidae)

“…OcomOBP7 is not differentially expressed in male and female antennae and binds strongly to limonene, a-pinene, and ocimene, the major volatile components of Andromeda, suggesting that OcomOBP7 is involved in host localization processes [15]. SvelOBP15 is not differentially expressed in either sex and has a high binding affinity for linalool, nerolidol, and limonene, suggesting that it exerts its olfactory function by binding transported plant volatiles [69]. Similarly, RproOBP6 and RproOBP13 were expressed in both male and female antennae, indicating that they probably participate in behaviors common to both sexes, such as host localization and the avoidance of natural enemies [20].…”