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Mechanical stimuli can affect plant growth, development, and defenses. The role of water spray stimulation, as a prevalent mechanical stimulus in the environment, in crop growth and defense cannot be overlooked. In this study, the effects of water spray on tomato plant growth and defense against the chewing herbivore Helicoverpa armigeraand necrotrophic fungus Botrytis cinereawere investigated. Suprathreshold water spray stimulus (LS) was found to enhance tomato plant defenses against pests and pathogens while concurrently modifying plant architecture. The results of the phytohormone and chemical metabolite analysis revealed that LS improved the plant defense response via jasmonic acid (JA) signaling. LS significantly elevated the level of a pivotal defensive metabolite, chlorogenic acid, and reduced the emissions of volatile organic compounds (VOCs) from tomato plants, thereby defending against pest and pathogen attacks. The most obvious finding to emerge from this study is that LS enhances tomato plant defenses against biotic stresses, which will pave the way for further work on the application of mechanical stimuli for pest management.

Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs), which are thought to play key roles in the olfactory recognition of insects, can be induced by the odorants they recognize, but little is known about the underlying regulatory mechanisms. Here, we found that NlOBP8 and NlCSP10 play coordinative roles in the chemoreception of brown planthoppers (BPHs) to the volatile component linalool. Also, the relative mRNA levels of NlObp8and NlCp10decreased upon exposure to linalool. Further, homeotic protein distal-less (Dll), which was also highly expressed in the antennae, was found to positively regulate the transcription of NlObp8and NlCsp10directly. Knocking down NlDllexpression downregulated the expression of many additional olfactory functional genes and impaired the repellent behavior of BPHs to linalool. Our findings elucidate the direct regulatory role of Dll in BPHs’ olfactory plasticity to linalool through modulating the olfactory functional gene expression and could provide guidance to sustainably control BPHs in the field.

Epicuticular wax plays an important part in protecting plant aerial organs from biotic and abiotic stresses. Nitrogen is the key limiting nutrient for crops and influences metabolite synthesis. However, how nitrogen influences wax composition on rice leaf and sheath at different growth stages has not been systematically examined. In this study, a total of 19 wax compounds in rice leaf and sheath were detected by using gas chromatography–mass spectrometry. Permutational multivariate analysis of variance (PermANOVA) indicated a significant influence of both nitrogen and growth stage on rice leaf and sheath wax composition. Nitrogen influenced wax composition on leaf and sheath mainly at 70 and 110 d, while the growth stage significantly influenced wax composition under all nitrogen levels. Our study provides the first report that rice wax composition changes with nitrogen and growth stage. This may support exploring nitrogen application and the associated ecological effects.

Odorant binding proteins (OBPs) play an important role in insect peripheral olfactory systems and exploring the physiological function of OBPs could facilitate the understanding of insects’ chemical communication. Here, the functional analysis of an antenna-based NlugOBP8 from brown planthopper (BPH) Nilaparvata lugens(Stål) was performed both in vitro and in vivo. Recombinant NlugOBP8 exhibited strong binding affinity to 13 out of 26 rice plant volatiles and could form a stable complex with 9 of them according to the fluorescence binding and fluorescence quenching experiments. Circular dichroism spectra demonstrated that six volatiles could give rise to significant conformational change of recombinant NlugOBP8. H-tube olfactometer bioassay confirmed that BPHs were significantly attracted by nerolidol and significantly repelled by linalool, caryophyllene oxide, and terpinolene, respectively. Antennae of dsNlugOBP8-injected BPHs exhibited significantly lower electrophysiological response to linalool and caryophyllene oxide. Moreover, the repellent responses of BPHs to these two volatiles were also impaired upon silencing NlugOBP8. These data suggest that NlugOBP8 is involved in recognizing linalool and caryophyllene oxide and provide additional target for the sustainable control of BPHs.

Ants easily accumulate cadmium (Cd) from the food web in terrestrial ecosystems. Cd contamination may cause olfactory dysfunction and consequently disorders in the social behavior of ants. To explore the molecular mechanism underlying the effect of Cd exposure on the chemosensory process of ants, we characterized the Cd-induced variations in the expression of genes involved in chemoreception and electrophysiological and behavioral sensitivity to semiochemicals by using the red imported fire ant, Solenopsis invicta, as a model system. As a result, Cd exposure increased Cd accumulation and decreased the survival rate of S. invicta. Cd exposure altered the expression profiles of odor binding protein genes of S. invicta(SiOBPs). Specifically, SiOBP15 protein expression was upregulated upon Cd exposure. Both SiOBP7 and SiOBP15 exhibited high binding affinities to limonene, nonanal, and 2,4,6-trimethylpyridine. S. invictaexposed to Cd showed less sensitive electrophysiological and behavioral response to the three chemicals but exhibited sensitive perception to undecane. Silencing of SiOBP7 and SiOBP15 abolished the behavioral response of S. invictato nonanal and undecane, respectively, suggesting that SiOBP7 and SiOBP15 play essential roles in the chemoreception of S. invicta. In general, our results suggest that Cd contamination may interfere with olfactory signal transduction by altering the expression of SiOBPs, consequently evoking chemosensory dysfunction in fire ants.

Nitrogen and phytopathogen alter plant organic volatiles that attract insect herbivores and their natural enemies. However, the interactive effects of nitrogen input and pathogen infection on volatile-mediated insect behavior are poorly understood. This study evaluates the impact of nitrogen application and bacterial blight Xanthomonas oryzae pv. oryzae (Xoo) on tri-trophic interactions involving rice plant, the brown planthopper Nilaparvata lugens, and its egg parasitoid Anagrus nilaparvatae on a temporal scale. Both N. lugens and A. nilaparvatae showed an obvious preference for Xoo-infected rice plants, but such preferences depended on nitrogen application. With prolonged Xoo infection and nitrogen fertilizer input, N. lugens and A. nilaparvatae preferred Xoo-infected plants. One possible mechanism was that the input nitrogen increased plant resistance to Xoo, which thus delayed the impact of Xoo infection on behavior of N. lugens and A. nilaparvatae. Further analyses indicated that the plant phytohormone JA regulated rice volatiles composition altering N. lugens preference, while SA regulated N. lugens-induced rice volatiles composition altering A. nilaparvatae preference. Moreover, with the development of the disease, Xoo infection had greater effects on plant volatiles and phytohormones than nitrogen fertilizer. Together, this finding provides new insights into how nitrogen application interacts with Xoo infection to modulate interactions among rice plants, N. lugens, and A. nilaparvatae.

Chemosensory proteins (CSPs) are important molecular components of the insect olfactory system, which are involved in capturing, binding, and transporting hydrophobic odour molecules across the sensillum in sensillar lymph in regulating insect behavior. This protein family (CSPs) is also involved in many other systems that are not linked to olfactory receptors in olfactory sensilla. The brown planthopper (BPH) is a monophagous pest of rice that causes damage by sucking phloem sap and transmitting a number of diseases caused by viruses. In this study, fluorescence competitive binding assay and fluorescence quenching assay at acidic pH were performed as well as homology modelling to describe the binding affinity of NlugCSP10. Fluorescence competitive binding assay (FCBA) demonstrated that NlugCSP10 bound strongly to nonadecane, farnesene, and 2-tridecanone at acidic pH. The results of FCBA indicated that NlugCSP10 bound different ligands at the physiological pH (5.0) of the bulk sensillum lymph. Fluorescence quenching assay demonstrated that NlugCSP10 generated a stable complex with 2-tridecanone, while two ligands nonadecane and farnesene collided due to molecular collisions. The interaction of selected ligands with the modelled structure of NlugCSP10 was also analyzed, which found the key amino acids (Gln23, Gln24, Gln25, Asn27, Met33, Ser34, Ile35, Tyr36, Asn42, Met43, Val45, Asn46, Asn93, Arg96, Ala97, Lys99, and Ala100) in NlugCSP10 that were involved in binding of volatile compounds. The present study contributes to the binding profile of NlugCSP10 that promotes the development of behaviorally active ligands based on BPH olfactory system.

Highly fluorinated candidates containing anticancer pharmacophores like thiosemicarbazone (5a–e) and its cyclic analogues hydrazineylidenethiazolidine (6a–e), 2-aminothiadiazole (7a–e), and 2-hydrazineylidenethiazolidin-4-one (8a–e) were synthesized, and their cytotoxic activity was assayed against 60 tumor cell lines. Compounds 6c, 7b, and 8bdisplayed the most potent activity with lower toxic effects on MCF-10a. In vitrophosphatidylinositol 3-kinase (PI3K) enzyme inhibition was performed. Compound 6cdisplayed half-maximal inhibitory concentration (IC50, μM) values of 5.8, 2.3, and 7.9; compound 7bdisplayed IC50values of 19.4, 30.7, and 73.7; and compound 8bdisplayed IC50values of 77.5, 53.5, and 121.3 for PI3Kα, β, and δ, respectively. Moreover, cell cycle progression caused cell cycle arrest at the S phase for compounds 6cand 8band at G1/S for compound 7b, while apoptosis was induced. In silicostudies; molecular docking; physicochemical parameters; and absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis were performed. The results showed that compound 6cis the most potent one with a selectivity index (SI) of 39 and is considered as a latent lead for further optimization of anticancer agents.

AbstractEncarsia formosais a parasitoid wasp, which has been extensively employed worldwide for controlling whitefly pests. There is a growing body of literature that recognises the importance of studying the morphological features and distributions of the antennal sensilla of parasitoids. The research data for this study were obtained by the JOEL JSM-6390LV scanning electron microscope. Results showed that the antenna of E. formosais comprised of nine antennomeres, which includes six flagella, a pedicel, a scape and a radicle. This study identified and described eight types of sensilla: (1) Nonporous sensilla trichodea; and (2) Uniporous sensilla trichodea (ST-UP) which both are two subtypes of sensilla trichodea; (3) Multiporous sensilla placoid which could be clearly observed due to the largest size compared with other types of sensilla; (4) Chaetica sensilla which looks similar to ST-UP but could be distinguished by the apical pore; (5) Uniporous rod-like sensilla (RO-UP); and (6) Nonporous finger-like sensilla (FL-NP) which both are located in the exploration area of the distal flagellum; (7) The RO-UP sensilla which have a rod-like shape; and (8) The FL-NP which are inserted into bulbous stalks.

Hamiltonella defensais mainly vertically transmitted, but evidence suggests that horizontal transmission may occur. Here, the first case of plant-mediated horizontal transmission of H. defensabetween wheat aphids, Sitobion miscanthi, was reported. H. defensawas harbored in sheath cells, secondary bacteriocytes, and hemolymph. After Hamiltonella-infected aphids fed on wheat leaves, H. defensawas observed in aphid stylets and plant phloem. H. defensapersisted in wheat leaves for at least 10 days. Most Hamiltonella-uninfected aphids became infected with H. defensaafter sustained feeding on infected plant leaves and showed almost 100% stable vertical transmission over the next five generations. These horizontal transmission experiments were replicated using two other plants, rice and corn, and two different wheat aphid species, Rhopalosiphum padiand Schizaphis graminum. Surprisingly, aphid feeding induced plant infection only locally rather than systemically in leaves. Our findings indicate that plants may act as horizontal transmission intermediaries, contributing to the ubiquity of the otherwise maternally inherited H. defensa.

The impact of the expression of Bacillus thuringiensis protoxins in the T1C-19 (cry1C) and T2A-1 (cry2A) transgenic rice strains on the brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), was evaluated by comparing the population densities of N. lugens reared on the strains T1C-19 or T2A-1 or the parental non-Bt strain Minghui 63. Field investigations revealed that the population densities of N. lugens were similar among the T2A-1, T1C-19, and Minghui 63 rice fields. Further assessment of feeding behavior of N. lugens using electrical penetration graph (EPG) technology showed that all four strains are susceptible to N. lugens, which was evidenced by the non-significant difference in feeding behavior of N. lugens between the transgenic and non-transgenic rice plants. These results provide new evidence that Bt rice does not pose any risk on N. lugens which represents a key non-target pest species in Bt rice field in China.

AbstractChemoreception is a key process for insects. Odorant messages diffuse through the air and are translated into physiological signals by chemosensory receptor neurons in sensilla that are mainly located on insect antennae. We sequenced the antenna transcriptome of Rhyzopertha dominica(Fabricius) (Coleoptera: Bostrichidae), which is a serious pest of stored grains throughout regions with warm climates, and performed transcriptome analysis on R. dominicaantennae. We obtained 57 million 90-base pair-long reads that we assembled into 37 877 unigenes with a mean size of 1007 base pairs. Predicted protein sequences were matched with Tribolium castaneum(Herbst) (Coleoptera: Tenebrionidae) (79.1%), Dendroctonus ponderosaeHopkins (Coleoptera: Curculionidae) (1.7%), Megachile rotundata(Fabricius) (Hymenoptera: Megachilidae) (1.3%), Acyrthosiphon pisumHarris (Hemiptera: Aphididae) (1.2%), and other (16.7%) homologues. In chemosensory gene families, we identified transcripts that encoded the following putative genes: 12 odorant-binding proteins (OBPs), four pheromone-binding proteins (PBPs), eight chemosensory proteins (CSPs), five sensory neuron membrane proteins (SNMPs), six odorant receptors, and eight ionotropic receptors. The diversity of the predicted OBPs, PBPs, and CSPs are also discussed. These findings will advance our understanding of olfaction process by this pest.

Chemoreception is a key feature in the selection of host plants by insects. In our current study, we identified two olfactory genes in Frankliniella occidentalis(Pergande), one encoding a putative pheromone binding protein (PBP) and the other one encoding a chemosensory protein (CSP), through an analysis of an antennal cDNA library. The expression profiles of both genes were examined in tissues of the antennae, abdomen, legs, and wings using quantitative reverse transcription and real-time polymerase chain reaction. We found that the PBP and CSP genes were expressed ubiquitously during various developmental stages of F. occidentalis. However, the levels of PBP and CSP transcripts in males were higher than those in females. The levels of PBP and CSP gene expression in adult F. occidentalisalso varied with age. These findings support the hypothesis that odorant binding proteins and CSPs play dynamic roles in the development of F. occidentalis, and are likely to be involved in broader physiological processes.

Helicoverpa armigerashowed strong protogynous emergence in its response to photoperiod and temperature, the induction of diapause in females was higher than males and the duration of non-diapausing male pupae was significantly longer than females. There was no difference in the larval duration between the sexes, and significant interactions with the photoperiod and temperature were observed.