Characterization of the Expression and Functions of Two Odorant-Binding Proteins of Sitophilus zeamais Motschulsky (Coleoptera: Curculionoidea)

Abstract

Odorant-binding proteins (OBPs) are important in insect chemical communication. The objective of this research was to identify the functions of two OBPs in Sitophilus zeamais. qRT-PCR and western blot (WB) were performed to investigate the expression profiles at the transcript and protein levels, respectively. Fluorescence competitive binding assays were used to measure the ability of the OBPs to bind to host volatiles, and a Y-tube olfactometer was used to verify the results (attraction/no response) via behavioral experiments. The RNAi was used to verify the function by knocking down the ability of proteins to bind odorants. qRT-PCR showed the highest expression SzeaOBP1 and SzeaOBP28 at the low-instar larva (LL) and eclosion adult (EA) stages, respectively. WB showed that both SzeaOBP1 and SzeaOBP28 were highly expressed in the EA stage. Fluorescence competitive binding assays indicated that SzeaOBP1 exhibited extremely high binding affinity with cetanol. SzeaOBP28 exhibited a pronounced binding affinity for 4-hydroxy-3-methoxybenzaldehyde. The behavioral experiment showed that the adult S. zeamais responded strongly to 4-hydroxy-3-methoxybenzaldehyde and valeraldehyde from Sorghum bicolor. The RNAi knockdown individuals displayed behavioral differences between normal insects and dsRNA (SzeaOBP1)-treated insects. We infer that they both have functions in perception and recognition of host volatiles, whereas SzeaOBP28 may also have other functions.

Characterization of Antennal Chemosensilla and Associated Chemosensory Genes in the Orange Spiny Whitefly, Aleurocanthus spiniferus (Quaintanca)

“…Similarly, in Sitophilus zeamais , SzeaOBP1 showed highest expression at larval stage, while the expression of SzeaOBP28 at pupae and adult stage was significantly higher than that at larval stage ( Zhang Y. et al, 2019 ). Furthermore, SzeaOBP1 showed broader binding affinity for plant volatile compounds than SzeaOBP28 ( Zhang Y. et al, 2019 ). Silencing SzeaOBP1 reduced the preference of S. zeamais to its preferred volatiles ( Zhang Y. et al, 2019 ).…”

“…Furthermore, SzeaOBP1 showed broader binding affinity for plant volatile compounds than SzeaOBP28 ( Zhang Y. et al, 2019 ). Silencing SzeaOBP1 reduced the preference of S. zeamais to its preferred volatiles ( Zhang Y. et al, 2019 ). In B. tabaci , BtabOBP1 , BtabOBP2 , BtabOBP3 , BtabOBP4 , BtabOBP7 , and BtabOBP8 were highly expressed in heads whereas BtabOBP5 predominately expressed in legs and wings.…”

Functional characteristic analysis of three odorant‐binding proteins from the sweet potato weevil (Cylas formicarius) in the perception of sex pheromones and host plant volatiles

“…Four gas‐washing cylinders were successively connected with a flow meter, drying tower and air pump through rubber pipes. To avoid the effects of light and temperature on the behavioral assay, the evaluations were performed in a room under dim light supplied by a red fluorescent tube with no natural lighting at 27 ± 1 °C and 70% RH 36 . The solutions of the odorant components were prepared in the solvent (solvent oil) at different concentrations (0.01, 0.05, 0.1, 0.2, 0.5 and 1 g mL −1 ) and solvent oil solution was used as the control in preliminary experiments.…”

“…29 There are many ways to import dsRNA interference fragments, and the three most common RNAi experiments are microinjection, ingestion and soaking. 30,31 One feeding method is to directly provide insects with in vitro synthesized dsRNA either through feed or solution; this method has been successful in experiments with Coleoptera insects such as Tribolium castaneum, 32 Cylas puncticollis, 33 Phyllotreta striolata, 34 Leptinotarsa decemlineata, 35 Diabrotica virgifera, 36 Adalia bipunctata and Coccinella septempunctata. 37 In the present study, we identified and analyzed three OBP genes from the antennae transcription library of C. formicarius, as the expression of the three OBPs was significantly higher in both male and female antennae than in other tissues.…”

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

“…The olfactory proteins n insects, such as OBPs and ORs, represent potential molecular targets that can be used to discover novel potent semiochemicals for environmental-friendly approaches in pest management ( Venthur and Zhou, 2018 ). In recent years, an increasing number of olfactory-sensing genes in coleopterans have been identified based on the development of high-throughput sequencing technology including a few weevil species (including but not limited to Rhynchophorus ferrugineus , Dendroctonus ponderosae , Cylas formicarius , Lissorhoptrus oryzophilus , Eucryptorrhynchus scrobiculatus and E. brandti ) ( Andersson et al, 2013 ; Antony et al, 2016 ; Yuan et al, 2016 ; Bin et al, 2017 ; Wen et al, 2018 ; Andersson et al, 2019 ; Zhang Y. et al, 2019 ). However, little is known regarding any chemosensory genes in S. velatus.…”