Identification of odorant-binding protein genes inGaleruca daurica(Coleoptera: Chrysomelidae) and analysis of their expression profiles

Abstract

Odorant-binding proteins (OBPs) play a fundamental role in insect olfaction. In recent years, Galeruca daurica (Joannis) (Coleoptera: Chrysomelidae) has become one of the most important insect pests in the Inner Mongolian grasslands of China. This pest only feeds on the species of Allium plants, implying the central role of olfaction in its search for specific host plants. However, the olfaction-related proteins have not been investigated in this beetle. In this study, we identified 29 putative OBP genes, namely GdauOBP1-29, from the transcriptome database of G. daurica assembled in our laboratory by using RNA-Seq. All 29 genes had the full-length open reading frames except GdauOBP29, encoding proteins in length from 119 to 202 amino acids with their predicted molecular weights from 12 to 22 kDa with isoelectric points from 3.88 to 8.84. Predicted signal peptides consisting of 15-22 amino acid residues were found in all except GdauOBP6, GdauOBP13 and GdauOBP29. The amino acid sequence identity between the 29 OBPs ranged 8.33-71.83%. GdauOBP1-12 belongs to the Classic OBPs, while the others belong with the Minus-C OBPs. Phylogenetic analysis indicated that GdauOBPs are the closest to CbowOBPs from Colaphellus bowringi. RT-PCR and qRT-PCR analyses showed that all GdauOBPs were expressed in adult antennae, 11 of which with significant differences in their expression levels between males and females. Most GdauOBPs were also expressed in adult heads (without antennae), thoraxes, abdomens, legs and wings. Moreover, the expression levels of the GdauOBPs varied during the different development stages of G. daurica with most GdauOBPs expressed highly in the adult antennae but scarcely in eggs and pupae. These results provide insights for further research on the molecular mechanisms of chemical communications in G. daurica.

Characterization of MaltOBP1, a Minus-C Odorant-Binding Protein, From the Japanese Pine Sawyer Beetle, Monochamus alternatus Hope (Coleoptera: Cerambycidae)

“…Analyzing expression patterns of OBPs could better help us to understand the functions of these proteins. Many studies have shown that most insect OBPs are mainly expressed in the antennae of both sexes, demonstrating that they might be involved in olfactory functions (Li L. et al, 2017;Zhang et al, 2017;He et al, 2019). Our western blot experiments show that MaltOBP1 is predominantly expressed in the antennae, legs and wings of both sexes.…”

“…Studies involving OBP identification (Li L. et al, 2017;Zhao et al, 2018), protein structural analysis (Northey et al, 2016;Falchetto et al, 2019), immunocytochemistry in specific olfactory sensilla Zhang et al, 2018), ligand binding properties (Sun et al, 2017(Sun et al, , 2018, and in vivo RNA interference (Yin et al, 2018;He et al, 2019) have demonstrated that insect OBPs play crucial roles in odorant discrimination, binding, and transportation. These proteins carry lipophilic odorants to the olfactory receptor cells in the sensillar lymph surrounding the sensory dendrite (Pelosi et al, 2014(Pelosi et al, , 2018.…”

Systemic and sex-biased regulation of OBP expression under semiochemical stimuli

“…The atypical OBP resembled two fused OBPs with predicted size of approximately 24 kDa, has additional conserved cysteines in an extended C-terminal region 75 , but lacked the fifth conserved Cys and has no signal-peptide in the N-terminal end. Other coleopterans also were observed with most of the OBPs assigned as Minus-C 55 , 56 , 61 , 66 , 72 , 76 . The Plus-C pattern was also not identified in the other coleopterans 60 – 62 , 72 .…”

“…Some AgraOBPs were smaller ( e.g ., AgraOBP15 was the smallest with 105 aa), with basic pI (AgraOBP9 = 8.88), or without the predicted signal peptide (AgraOBP2 and AgraOBP4). Others reported coleopteran OBPs that were smaller than typical 54 , 62 – 69 , have a basic pI 66 , 68 , 70 – 72 , or lack the signal peptide 56 , 57 , 59 , 62 , 66 , 67 .…”

Silencing the Odorant Binding Protein RferOBP1768 Reduces the Strong Preference of Palm Weevil for the Major Aggregation Pheromone Compound Ferrugineol

“…Although substantial antennal transcriptome data are available for coleopteran insects (Dippel et al, 2014 ; Liu et al, 2015 , 2018 ; Li X. et al, 2015 ; Li X.M. et al, 2015 ; Li K. et al, 2017 ; Li L. et al, 2017 ), PBPs from scarab beetle and Japanese beetle are the only coleopteran OBPs identified thus far (Wojtasek et al, 1998 ; Nikonov et al, 2002 ). However, their functional characterization has not been reported, and hence there is much work needed in exploring the olfactory mechanism in beetles and the pattern of OBP relatedness between beetles.…”