The belowground pest Bradysia odoriphaga (Diptera: Sciaridae) has a sophisticated and sensitive olfactory system to detect semiochemical signals from the surrounding environment. In particular, odorant-binding proteins (OBPs) are crucial in capturing and transporting these semiochemical signals across the sensilla lymph to the corresponding odorant receptors. In this study, we cloned a full-length cDNA sequence of BodoOBP8 from B. odoriphaga. Real-time PCR (qRT-PCR) analysis revealed that BodoOBP8 has the highest expression levels in males, with more pronounced expression in the male antennae than in other tissues. In this study, the recombinant protein BodoOBP8 was successfully expressed by a bacterial system to explore its function. Competitive binding assays with 33 host plant volatiles and one putative sex pheromone (n-heptadecane) revealed that purified BodoOBP8 strongly bound to two sulfur compounds (methyl allyl disulfide and diallyl disulfide) and to n-heptadecane; the corresponding dissolution constants (Ki) were 4.04, 6.73, and 4.04 μM, respectively. Molecular docking indicated that Ile96, Ile103, Ala107, and Leu111, located in the hydrophobic cavity of BodoOBP8, are the key residues mediating the interaction of BodoOBP8 with two sulfur compounds (methyl allyl disulfide and diallyl disulfide) and n-heptadecane. These results show that BodoOBP8 plays a role in the recognition of plant volatiles and sex pheromones, suggesting its application as a molecular target for the screening of B. odoriphaga attractants and repellents and facilitating a new mechanism of B. odoriphaga control.
The whitefly Bemisia tabaci is a piercing-sucking herbivore that reduces the yields of crops both by feeding on plants and transmitting plant viruses. Like most plant feeders, B. tabaci has evolved ways to avoid plant defense responses. For example, B. tabaci is known to secrete salivary effectors to suppress host defenses. However, the nature of B. tabaci effectors is incompletely understood. In this study, we used B. tabaci genomic and salivary gland transcriptomic data and an overexpression system to identify a previously unknown B. tabaci salivary effector, BtE3. BtE3 is specifically expressed in the head (containing primary salivary glands) and is secreted into hosts during B. tabaci feeding. In planta overexpression of BtE3 blocked Burkholderia glumae-induced hypersensitive response (HR) in both Nicotiana benthamiana and Solanum lycopersicum. Silencing of BtE3 by plant-mediated RNAi prevented whiteflies from continuously ingesting phloem sap and reduced whitefly survival and fecundity. Moreover, over-expression of BtE3 in planta upregulated the salicylic acid- (SA-) signaling pathway but suppressed the downstream jasmonic acid- (JA-) mediated defenses. Taken together, these results indicate that BtE3 is a whitefly-specific novel effector involved in whitefly-plant interactions. These findings increase our understanding of whitefly effectors and suggest novel strategies for whitefly pest management.
The herbaceous peony (Paeonia lactiflora Pall.) has high ornamental and nutritional value, and the seeds of P. lactiflora can be used to produce high-quality edible oil. However, low seed yield limits the application of P. lactiflora. This can be mitigated by insect pollinators. Here, we evaluated the pollination services of honeybees (Apis mellifera L.) in a P. lactiflora field. We found that A. mellifera provided pollination for P. lactiflora throughout the day especially in the period from 10:00–15:00. Seed number and weight were significantly increased when P. lactiflora was pollinated by A. mellifera. Furthermore, a DNA barcode, the rbcL gene, was used to analyze pollen samples from the corbiculae (pollen baskets) of A. mellifera (bee pollen, BP) and P. lactiflora flowers (flower pollen, FP). High homology of rbcL genes in the BP and FP suggested that BP was collected from P. lactiflora. Based on our results, A. mellifera provided efficient pollination for P. lactiflora. Therefore, A. mellifera could be a good candidate pollinator for P. lactiflora and could be applied in the field.
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