Plant volatile organic compounds (VOCs) are an important link that mediates chemical communication between plants and plants, plants and insects, and plants and natural enemies of insect pests. In this study, we tested the response in the selective behavior of western flower thrips,Frankliniella occidentalis, to the VOCs of kidney bean,Phaseolus vulgarisL., to explore their “attraction” or “repellent” effects regarding their application in integrated pest management (i.e., IPM). The results indicated that 12.7 μL/mL (E, E, E, E)-squalene, 3.2 μL/mL dioctyl phthalate, and 82.2 μL/mL ethyl benzene had a significantly attractive effect on the selective behavior ofF. occidentalis, while 10.7 μL/mL and 21.4 μL/mL 2,6-ditert-butyl-4-methyl phenol had a significantly repulsive effect on the selective behavior ofF. occidentalis, showing thatF. occidentalisresponds differently to specific concentrations of VOCs fromP. vulgarisplant emissions. Interestingly, the three compounds with the specific above concentrations, after being mixed in pairs, significantly attractedF. occidentaliscompared to the control treatment; however, the mixture with the three above compounds had no significant different effect onF. occidentaliscompared to the control treatment. It can be seen that the effect with the mixtures of three kinds of VOCs had the same function and may not get better. Simultaneously, the reasons for this result from the transcription levels of odorant-binding protein genes (OBPs) were determined. There were differences in the types and transcription levels of OBPs, which played a major role in the host selection behavior ofF. occidentalisunder the mixed treatment of different VOCs. It is presumed that there are specific VOCs fromP.vulgarisplants that have a good repellent or attracting effect on the selective behavior ofF.occidentalis, which can be used for the development of plant-derived insect attractants and repellents to serve as IPM in fields. But attention should be paid to the antagonism between plant-derived preparations and VOCs produced by plants themselves after application.Keywords:Phaseolus vulgarisL.;Frankliniella occidentalis;VOCs;attractive and repellant effects;selection behavior
Zhang Yonglei,Gao Shanshan,Zhang Ping,Sun Haidi,Lu Ruixue,Yu Runnan,Li Yanxiao,Zhang Kunpeng,Li Bin
Eugenol, a plant-derived component possessing small side effects, has an insecticidal activity to Tribolium castaneum ; however, the underlying molecular mechanisms of eugenol acting on T. castaneum are currently unclear. Here, a nerve conduction carboxylesterase and a detoxifying glutathione S-transferase were significantly inhibited after eugenol exposure, resulting in the paralysis or death of beetles. Then, RNA-sequencing of eugenol-exposed and control samples identified 362 differentially expressed genes (DEGs), containing 206 up-regulated and 156 down-regulated genes. RNA-seq data were validated further by qRT-PCR. GO analysis revealed that DEGs were associated with 1308 GO terms of which the most enriched GO terms were catalytic activity, and integral component of membrane; KEGG pathway analysis showed that these DEGs were distributed in 151 different pathways, of which some pathways associated with metabolism of xenobiotics or drug were significantly enriched, which indicated that eugenol most likely disturbed the processes of metabolism, and detoxication. Moreover, several DEGs including Hexokinase type 2 , Isocitrate dehydrogenase , and Cytochrome b-related protein , might participate in the respiratory metabolism of eugenol-exposed beetles. Some DEGs encoding CYP , UGT , GST , OBP , CSP , and ABC transporter were involved in the xenobiotic or drug metabolism pathway, which suggested that these genes of T. castaneum participated in the response to eugenol exposure. Additionally, TcOBPC11/ TcGSTs7 , detected by qRT-PCR and RNA-interference against these genes, significantly increased the mortality of eugenol-treated T. castaneum , providing further evidence for the involvement of OBP/GST in eugenol metabolic detoxification in T. castaneum . These results aid eugenol insecticidal mechanisms and provide the basis of insect control.
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