Spatial Expression Analysis of Odorant Binding Proteins in Both Sexes of the Aphid Parasitoid Aphidius gifuensis and Their Ligand Binding Properties

Abstract

In China, Aphidius gifuensis is one of the most common endoparasitoids of the green peach aphid Myzus persicae and grain aphid Sitobion miscanthi in the field. Insect odorant-binding proteins (OBPs) play vital roles in odor perception during feeding, host searching, mating and oviposition. In addition, some OBPs are involved in other physiological processes such as gustation and reproduction. In the present study, a comparative antennal transcriptomic analysis was applied between male and female A. gifuensis. The spatial expression patterns among antennae, heads, thoraxes, abdomens and legs of OBPs in both sexes were further profiled. Fifteen AgifOBPs were predicted, and 14 of them were identified by gene cloning, including 12 classic OBPs and 2 min-C OBPs. As expected, all OBPs were mainly expressed at high levels in antennae, heads or legs which are sensory organs and tissues. Finally, ligand binding properties of 2 OBPs (AgifOBP7 and AgifOBP9) were further evaluated. Female leg specifically expressed AgifOBP9 displays a broad and high binding property to aphid alarm pheromones, plant green volatiles and aphid sex pheromones (Ki < 10 μΜ). However, female leg specifically expressed AgifOBP7 displays poor affinity for all tested ligands except CAU-II-11 ((E)-3,7-dimethylocta-2,6-dien-1-yl-2-hydroxy-3-methoxybenzoate), a reported (E)-β-farnesene (EBF) analog with an exceptionally high binding affinity (Ki = 1.07 ± 0.08 μΜ). In summary, we reported the spatial expression pattern of the OBP repertoire in A. gifuensis, and further studied the binding properties of OBP7 and OBP9, which are mainly expressed in female legs, laying the foundation for the dissection of the contribution of OBPs to chemosensation in A. gifuensis.

Functional analysis of odorant-binding proteins for the parasitic host location to implicate convergent evolution between the grain aphid and its parasitoid Aphidius gifuensis

“…Parasitoid wasps (A. gifuensis) were originally collected from M. persicae mummies in August 2019 in Kunming, Yunnan Province, China, and they had been cultured on S. miscanthi, which are parthenogenic clones (Langfang-1) reared on wheat (T. aestivum L.) 'AK58' at our laboratory at the Institute of Plant Protection of Chinese Academy of Agricultural Sciences (Beijing, China) for 2 years with an airconditioned insectary: 23 ± 2 • C with 55 ± 10 % relative humidity and a photoperiod of 16:8 (L: D) h. The detailed rearing methods were described in previous works [20,49].…”

“…Real-time quantitative PCR (RT-qPCR) with an ABI 7500 real-time PCR system (Applied Biosystems Fosters City CA, USA) was conducted to explore the responses of AgifOBPs at the mRNA level after induction with EBF. Primers were described in our previous work [49] and used a 20-μL reaction containing 10 μL of 2 × SuperReal PreMix Plus, 0.6 μL of forward primer (10 μmol/L), 0.6 μL of reverse primer (10 μmol/L), 2 μL of cDNA (50 ng/μL), 0.4 μL of 50 × ROX reference dye, and 6.4 μL of nuclease-free ddH 2 O following the instructions provided with the Su-perReal PreMix Plus (SYBR Green) kit (FP205) (Tiangen, Beijing, China). The PCR program was as follows: an initial 15-min step at 95 C for 45 s, and finally a 10-min step at 72 • C. For melting curve analysis, a dissociation step cycle was added automatically.…”

“…In addition, the intense sexual orientation of males to females in distance indicated the existence of sex pheromones [20]. Our previous work incidentally identified two OBPs with medium or weak affinity for EBF in A. gifuensis [49]. However, the molecular mechanism underlying the attraction to parasitoids other than A. gifuensis of either EBF or any other olfactory cues remains completely unknown.…”

“…Aphid parasitoids, as natural enemies, can also detect EBF as well as plants being infested by host aphids [46][47][48][49][50]. A. gifuensis is one of the most common endoparasitoids of the tobacco aphid M. persicae and the wheat aphid S. miscanthi in China [50,51].…”

D-limonene binds the target gene odorant-binding protein 3 to control Bemisia tabaci

“…Insects rely on a sensitive and complex olfactory system to detect chemicals to complete their physiological behaviors (Hua et al 2013;Leal 2013Jiang et al 2022). In addition, odorant-binding proteins (OBPs) are important components of the olfactory system and the rst step in the signal chain of odorant perception (Xu et al 2009).…”