Hongsong Chen

The melon fly, Zeugodacus cucurbitae (Coquillett), is a globally significant agricultural pest causing substantial economic losses. Odorant-binding proteins (OBPs) are critical of the insect olfactory system, yet their specific physiological functions in Z. cucurbitae remain largely uncharacterized. In this study, we functionally characterized ZcucOBP14 and investigated its putative involvement in host chemoreception and insecticide tolerance. Sequence alignment and phylogenetic analysis indicated that ZcucOBP14 belongs to the Minus-C OBP subfamily, and quantitative reverse transcription PCR (RT-qPCR) showed that it was predominantly expressed in both the head and abdomen. Fluorescence binding assays revealed that ZcucOBP14 exhibited broad binding affinity to 11 host plant volatiles, three sex pheromones, and two insecticides. Subsequent electroantennography (EAG) and behavioral bioassays identified isopulegol, 1-hexanol, linalool, and α-pinene as key ligands regulating the behavioral responses of Z. cucurbitae. RNA interference (RNAi)-mediated knockdown of ZcucOBP14 significantly reduced EAG responses to key ligands, eliminated behavioral preference, and increased insecticide-induced mortality by 20%. Molecular docking further identified that Tyr71, Ile67, Trp50, Val107, Phe116 and Leu70 were critical residues involved in ligand interactions. Collectively, these findings highlight the indispensable role of ZcucOBP14 in olfactory perception and its contribution to insecticide tolerance, laying a solid theoretical foundation for the development of novel behavior-modifying agents, attractants, and optimized integrated pest management (IPM) strategies against this pest.

Aggregation behavior is common in insects, and plays a key role in population dynamics. Ophraella communa LeSage is an important biocontrol agent against common ragweed (Ambrosia artemisiifolia L.), yet its aggregation behavior and density-dependent responses remain poorly understood. This study examined aggregation and intersexual attraction in O. communa and evaluated the effects of larval densities on its development and reproduction using a 2-sex life table approach. Behavioral assays showed that both males and females were significantly attracted to conspecifics of either sex, with no difference in attractiveness between genders. Attraction responses were density-dependent, at low density (5 individuals), only males attracted females, whereas at high density (50 individuals), both sexes attracted conspecifics of both sexes. Life table analysis revealed that larval density significantly influenced the development and reproduction. At a density of 10 individuals per branch, larval and pre-adult stages shortened, adult longevity increased, and pupal and adult survival peaked. Fecundity was significantly higher at densities of 5 and 10, with the longest oviposition period at density 5. Life table parameters reached their maximum at density 10, while density 25 supported prolonged reproductive activity. Adult body weight, body length, and head width also varied with density. Males exhibited the highest body weight at a density of 10, while females showed the greatest body length and head width at the same density. This study enhances our understanding of the aggregation behavior and density-dependent population dynamics of O. communa, and provide basis for optimizing mass rearing to improve biological control of A. artemisiifolia.

MiR-71 has been determined to enhance the efficacy of biological control agents against termites. However, it is not clear how miR-71 functions in enhancing the termite control. In this study, we tested the effects of termite miR-71 on the transcriptional and translational profiles of termites via the commercial product miR-71 agomir, and meanwhile developed a cost-effective method using T7 RNA polymerase to synthesize a miR-71 mimic, comparing the effects of the T7-synthesized miR-71 mimic versus the commercial miR-71 agomir on the gene expressions and infection mortality of termites. Comparative bioassays demonstrated that both miR-71 mimic and agomir significantly increased fungus-induced termite mortality with equivalent bioactivity. Mechanistically, transcriptomic and proteomic analyses revealed that commercial miR-71 agomir modulated the expression of defense-related genes, such as hexamerin-1, neuroligin-4, and probable chitinase-10. Meanwhile, RT-qPCR confirmed that T7-synthesized miR-71 mimic induced similar expression changes in the same target genes. Additionally, the dsRNA-mediated silencing of hexamerin-1, neuroligin-4, and probable chitinase-10 made termites more vulnerable to the fungus, respectively. Our study establishes in vitro-transcribed miRNA mimics as potent and cost-effective tools for studying ‘miRNA–mRNA’ interaction, and meanwhile lays the foundation for the microbe-mediated expression of small-RNA mimics in enhancing termite biocontrol.

Insect olfactory receptor co-receptor (Orco) plays a key role in olfactory organ formation and odor recognition during insect growth and development. In predatory insects, the olfactory system is important for the orientation, identification, and selection of hosts or prey. The cloning of the Orco gene in Chrysopa pallens (Rambur) holds significant importance, enabling evolutionary comparisons of olfactory systems among Neuroptera insects and opening possibilities for developing Orco-based biological control strategies through the manipulation of odor perception. The olfactory recognition mechanisms of the lacewing, C. pallens (Rambur), are poorly understood. One of the more significant findings to emerge from this study is that we cloned and sequenced the full-length Orco gene (CpalOrco) from C. pallens. It has been demonstrated that CpalOrco is highly conserved and similar to Orco genes of coleopterous insects. Real-time quantitative PCR analysis showed that CpalOrco was mainly expressed in C. pallens antenna. Compared to the control group injected with dsRNA targeting enhanced green fluorescent protein (dsEGFP), RNA interference-mediated silencing of CpalOrco through targeted double-stranded RNA (dsOrco) delivery resulted in significant suppression of gene expression. Experimental evidence from electroantennogram assays indicated that downregulation of CpalOrco transcripts substantially compromised the olfactory perception of nonanal in C. pallens. Overall, the current study has confirmed that CpalOrco may play an important role in the C. pallens odor recognition process.

The olfactory system plays a key role in various insect behaviors, and odorant-binding proteins participate in the first step of the olfactory process. Ophraella communa Lesage is an oligophagous phytophagous insect that is a specific biological control agent for Ambrosia artemisiifolia L. The leaf beetle must identify and locate A. artemisiifolia through olfaction; however, its odorant-binding protein (OBP) function has not yet been reported. In this study, OcomOBP7 was cloned, and its tissue expression profile and binding ability were analyzed using RT-qPCR and fluorescence binding assays, respectively. Sequence analysis demonstrated that OcomOBP7 belongs to the classical OBP family. The RT-qPCR results showed that OcomOBP7 was specifically expressed in the antennae, indicating that OcomOBP7 may be involved in chemical communication. The fluorescence binding assay showed that OcomOBP7 has an extensive binding ability to alkenes. The electroantennography experiments showed that O. communa antennal response to α-pinene and ocimene decreased significantly after interference because the two odors specifically bound to OcomOBP7. In summary, α-pinene and ocimene are odorant ligands corresponding to OcomOBP7, indicating that OcomOBP7 is involved in the chemical recognition of A. artemisiifolia. Our study lays a theoretical foundation for research into O. communa attractants, which is helpful for the better biological control of A. artemisiifolia by O. communa.

The beetle Ophraella communa is an effective biological control agent against the invasive common ragweed spread across various ecosystems with variable temperature ranges. The trend in climate change attributed to fluctuating temperatures and abrupt rainfalls is expected to continue. This study aimed to better understand the effects of thermal fluctuation on O. communa by exposing all their life stages to heat stress under different treatments. Repeated exposure to high temperatures, relative to constant milder temperatures, increased the duration of immature development, mean generation time, and the adult longevity, decreased the intrinsic rate of increase, finite rate of population increase, net reproductive rate, survival rate, overall longevity, body length, and mass of adults and positively affected overall fecundity by prolonging the oviposition period, biasing sex ratio towards females. After exposure to heat stress, the mating success and production of viable offspring were higher in O. communa. Our findings demonstrate that exposure to heat stress negatively affects ragweed beetles, but they were able to survive and reproduce.

Ophraella communa is an efficient biocontrol agent used against the invasive weed Ambrosia artemisiifolia. It is an herbivorous insect that feeds on specific plants; the olfactory functions of this insects plays an important role in their search for host plants. There are no reports on O. communa sensilla types, morphology, or chemosensory protein (CSP) genes. In this study, we observed the external structure and distribution of antennal sensilla in adult O. communa antennae by scanning electron microscopy; moreover, we cloned 11 CSPs (CSP1–CSP11) and elucidated their tissue-expression profiles using quantitative real-time polymerase chain reaction. Six types of sensilla were identified: sensilla trichodea (including two subtypes), sensilla chaetica, sensilla basiconica (including two subtypes), sensilla styloconica, sensilla coeloconica, and Böhm bristles. Both male and female antennae had all six types of sensilla, and no sexual dimorphism was noted in sensillar types or distribution. We also found that the expression levels of CSP2, CSP3, CSP4, CSP6, and CSP7 in male and female antennae were higher than those in other tissues, which suggests that these five CSPs may be related to olfactory function in O. communa. Ultimately, our results lay the foundation for interpreting the olfactory functions of adult O. communa.

Concentrations of heavy metals continue to increase in soil environments as a result of both anthropogenic activities and natural processes. Cadmium (Cd) is one of the most toxic heavy metals and poses health risks to both humans and the ecosystem. Herein, we explore the impacts of Cd on a soil–plant system composed of oilseed rapes (Brassica napus and Brassica juncea) and bacteria. The results showed that Cd accumulation within tissues of two species of oilseed rapes enhanced with increasing concentrations of Cd in soils, and Cd treatment decreased their chlorophyll content and suppressed rapeseeds growth. Meanwhile, Cd stress induced the changes of antioxidative enzymes activities of both B. napus and B. juncea. Response to Cd of bacterial community was similar in soil-two species of oilseed rapes system. The impact of Cd on the bacterial communities of soils was greater than bacterial communities of plants (phyllosphere and endophyte). The α-diversity of bacterial community in soils declined significantly under higher Cd concentration (30 mg/kg). In addition, soil bacterial communities composition and structure were altered in the presence of higher Cd concentration. Meanwhile, the bacterial communities of bulk soils were significantly correlated with Cd, while the variation of rhizosphere soils bacterial communities were markedly correlated with Cd and other environmental factors of both soils and plants. These results suggested that Cd could affect both the growth of plants and the indigenous bacterial community in soil–plant system, which might further change ecosystem functions in soils.