Search

Plant Growth-Promoting Rhizobacteria (PGPR) induce systemic resistance (SR) in plants, decreasing the development of phytopathogens. The FZB42 strain of Bacillus velezensis is known to induce an SR against pathogens in various plant species. Previous studies suggested that it could also influence the interactions between plants and associated pests. However, insects have developed several strategies to counteract plant defenses, including salivary proteins that allow the insect escaping detection, manipulating defensive pathways to its advantage, deactivating early signaling processes, or detoxifying secondary metabolites. Because Brown Marmorated Stink Bug (BMSB) Halyomorpha halys is highly invasive and polyphagous, we hypothesized that it could detect the PGPR-induced systemic defenses in the plant, and efficiently adapt its salivary compounds to counteract them. Therefore, we inoculated a beneficial rhizobacterium on Vicia faba roots and soil, previous to plant infestation with BMSB. Salivary gland proteome of BMSB was analyzed by LC–MS/MS and a label-free quantitative proteomic method. Among the differentially expressed proteins, most were up-regulated in salivary glands of insects exposed to PGPR-treated plants for 24 h. We could confirm that BMSB was confronted with a stress during feeding on PGPR-treated plants. The to-be-confirmed defensive state of the plant would have been rapidly detected by the invasive H. halys pest, which consequently modified its salivary proteins. Among the up-regulated proteins, many could be associated with a role in plant defense counteraction, and more especially in allelochemicals detoxification or sequestration. [ABSTRACT FROM AUTHOR]

In the current context of global climate change, atmospheric carbon dioxide (CO2) concentrations are continuously rising with potential influence on plant–herbivore interactions. The effect of elevated CO2 (e CO2) on feeding behavior of corn leaf aphid, Rhopalosiphum maidis (Fitch) on barley seedlings Hordeum vulgare L. was tracked using electrical penetration graph (EPG). The nutrient content of host plant and the developmental indexes of aphids under e CO2 and ambient CO2 (a CO2) conditions were also investigated. Barley seedlings under e CO2 concentration had lower contents of crude protein and amino acids. EPG analysis showed the plants cultivated under e CO2 influenced the aphid feeding behavior, by prolonging the total pre-probation time of the aphids (wandering and locating the feeding site) and the ingestion of passive phloem sap. Moreover, fresh body weight, fecundity and intrinsic population growth rate of R. maidis was significantly decreased in e CO2 in contrast to a CO2 condition. Our findings suggested that changes in plant nutrition caused by e CO2, mediated via the herbivore host could affect insect feeding behavior and population dynamics. [ABSTRACT FROM AUTHOR]

Caterpillars produce oral secretions that may serve as cues to elicit plant defenses, but in other cases these secretions have been shown to suppress plant defenses. Ongoing work in our laboratory has focused on the salivary secretions of the tomato fruitworm, Helicoverpa zea. In previous studies we have shown that saliva and its principal component glucose oxidase acts as an effector by suppressing defenses in tobacco. In this current study, we report that saliva elicits a burst of jasmonic acid (JA) and the induction of late responding defense genes such as proteinase inhibitor 2 (Pin2). Transcripts encoding early response genes associated with the JA pathway were not affected by saliva. We also observed a delayed response to saliva with increased densities of Type VI glandular trichomes in newly emerged leaves. Proteomic analysis of saliva revealed glucose oxidase (GOX) was the most abundant protein identified and we confirmed that it plays a primary role in the induction of defenses in tomato. These results suggest that the recognition of GOX in tomato may represent a case for effector-triggered immunity. Examination of saliva from other caterpillar species indicates that saliva from the noctuids Spodoptera exigua and Heliothis virescens also induced Pin2 transcripts. [ABSTRACT FROM AUTHOR]

Barley yellow dwarf virus (BYDV), transmitted by the wheat aphid, generates serious wheat yellow dwarf disease and causes great losses in agriculture. Induced resistance has attracted great attention over recent years as a biological method to control plant pathogens and herbivores. Protein elicitor PeaT1 induces defense response in plants against fungi, viruses, and aphids. In this study, wheat seeds and seedlings were soaked and sprayed with 30 μg/mL PeaT1, respectively. Then seedlings were inoculated with BYDV by viruliferous Schizaphis graminum to detect the control efficiency of PeaT1-induced resistance against BYDV. The control efficiency was over 30% on the 14th and 21st days after the inoculation access period. Quantitative real time polymerase chain reaction (Q-RT-PCR) tests showed that there was less mRNA from the BYDV coat protein in PeaT1-treated wheat seedlings than in the control group. Electrical penetration graph (EPG) tests showed that virus transmission vector S.graminum took a longer time to find probe and feeding sites on PeaT1-treated wheat seedlings. Additionally, PeaT1-treated wheat seedlings gained higher plant height and more chlorophyll a&b. These results showed that PeaT1 efficiently controlled BYDV by inhibiting BYDV proliferation, reducing the virus transmission ability of S. graminum and alleviating the symptoms of dwarfism and yellow colouring caused by BYDV. This study provided a new integrated way to control BYDV biologically. [ABSTRACT FROM AUTHOR]