Airborne signals synchronize the defenses of neighboring plants in response to touch

Plants activate defense-related pathways in response to subtle abiotic or biotic disturbances, changing their vola-tile profile rapidly. How such perturbations reach and potentially affect neighboring plants is less understood. Weevaluated whether brief and light touching had a cascade effect on the profile of volatiles and gene expression of thefocal plant and a neighboring untouched plant. Within minutes after contact,Zea maysshowed an up-regulation ofcertain defense genes and increased the emission of specific volatiles that primed neighboring plants, making themless attractive for aphids. Exposure to volatiles from touched plants activated many of the same defense-relatedgenes in non-touched neighboring plants, demonstrating a transcriptional mirroring effect for expression of genesup-regulated by brief contact. Perception of so-far-overlooked touch-induced volatile organic compounds was ofecological significance as these volatiles are directly involved in plant–plant communication as an effective trigger forrapid defense synchronization among nearby plants. Our findings shed new light on mechanisms of plant responsesto mechanical contact at the molecular level and on the ecological role of induced volatiles as airborne signals inplant–plant interactions

Lessons from the Far End: Caterpillar FRASS-Induced Defenses in Maize, Rice, Cabbage, and Tomato

Plant defenses to insect herbivores have been studied in response to several insect behaviors on plants such as feeding, crawling, and oviposition. However, we have only scratched the surface about how insect feces induce plant defenses. In this study, we measured frass-induced plant defenses in maize, rice, cabbage, and tomato by chewing herbivores such as European corn borer (ECB), fall armyworm (FAW), cabbage looper (CL), and tomato fruit worm (TFW). We observed that caterpillar frass induced plant defenses are specific to each host-herbivore system, and they may induce herbivore or pathogen defense responses in the host plant depending on the composition of the frass deposited on the plant, the plant organ where it is deposited, and the species of insect. This study adds another layer of complexity in plant-insect interactions where analysis of frass-induced defenses has been neglected even in host-herbivore systems where naturally frass accumulates in enclosed feeding sites over extended periods of time

Transcriptomic and volatile signatures associated with maize defense against corn leaf aphid

Background: Maize (Zea mays L.) is a major cereal crop, with the United States accounting for over 40% of the worldwide production. Corn leaf aphid [CLA; Rhopalosiphum maidis (Fitch)] is an economically important pest of maize and several other monocot crops. In addition to feeding damage, CLA acts as a vector for viruses that cause devastating diseases in maize. We have shown previously that the maize inbred line Mp708, which was developed by classical plant breeding, provides heightened resistance to CLA. However, the transcriptomic variation conferring CLA resistance to Mp708 has not been investigated. Results: In this study, we contrasted the defense responses of the resistant Mp708 genotype to those of the susceptible Tx601 genotype at the transcriptomic (mRNA-seq) and volatile blend levels. Our results suggest that there was a greater transcriptomic remodeling in Mp708 plants in response to CLA infestation compared to the Tx601 plants. These transcriptomic signatures indicated an activation of hormonal pathways, and regulation of sesquiterpenes and terpenoid synthases in a constitutive and inducible manner. Transcriptomic analysis also revealed that the resistant Mp708 genotype possessed distinct regulation of ethylene and jasmonic acid pathways before and after aphid infestation. Finally, our results also highlight the significance of constitutive production of volatile organic compounds (VOCs) in Mp708 and Tx601 plants that may contribute to maize direct and/or indirect defense responses. Conclusions: This study provided further insights to understand the role of defense signaling networks in Mp708’s resistance to CLA

Hemolymph colony forming units for fall armyworm

Bacterial colony forming units (per uL) in response to different feeding substrates

Data from: Chemical cues linked to risk: cues from belowground natural enemies enhance plant defences and influence herbivore behaviour and performance

1. Chemical cues are essential for many ecological interactions. Previous studies of chemically mediated multitrophic interactions have typically focused on responses to cues from plants or herbivores aboveground. It is increasingly clear, however, that belowground cues and those produced by organisms at higher trophic levels also have ecological importance. Prey animals often avoid predator odours to improve survival, and previous research documented enhanced plant resistance following contact with belowground natural enemies, though the ecological basis was unknown. 2. Here we investigated plant and insect responses to chemical cues from belowground natural enemies and explored the ecological significance of these cues for multitrophic interactions. More specifically, we examined the influence of odours emitted by entomopathogenic nematodes (EPNs), a natural enemy of insect herbivores, on the performance and behaviour of their insect prey and the defence responses of nearby plants. 3. Our findings revealed that EPN-infected insect cadavers emit a characteristic blend of volatile compounds with bioactivity in plants and insects. EPN chemical cues influenced both performance and preference of a specialist herbivore, Colorado potato beetle (CPB, Leptinotarsa decemlineata), feeding on its host plant, potato (Solanum tuberosum). CPB larvae consumed less leaf tissue and gained less mass feeding on plants exposed to EPN cues compared to control plants. Female CPBs laid fewer eggs on plants with EPN cues than on controls, indicating deterrence by EPN cues or EPN-altered plant defences. 4. Plant defences were enhanced by exposure to live EPNs or EPN chemical cues. Potato plants exposed to EPN infective juveniles induced higher amounts of the defence hormone salicylic acid and had higher expression of the pathogen-resistance gene PR-1(PR4) in foliar tissue. Exposing plants to EPN cues primed induction of salicylic acid and jasmonic acid in response to feeding damage by CPB larvae. 5. These findings suggest that herbivores avoid cues from their EPN natural enemies and plants respond to the beneficial nematodes by enhancing systemic defences that reduce herbivore performance. This work has important implications for the chemical ecology of tritrophic interactions as we report that the third trophic level can play direct and indirect roles in plant defence

Helms et al 2019 FE data

Oviposition, Larval mass and leaf area consumed, JA and SA amounts in leaf tissue, expression of defense genes, volatiles produced. The excel file contains 6 sheets with all data from the publication organized by experiment. Data provided are not transformed

Data from: Plant defenses interact with insect enteric bacteria by initiating a leaky gut syndrome

Plants produce suites of defenses that can collectively deter and reduce herbivory. Many defenses target the insect digestive system, with some altering the protective peritrophic matrix (PM) and causing increased permeability. The PM is responsible for multiple digestive functions, including reducing infections from potential pathogenic microbes. In our study, we developed axenic and gnotobiotic methods for fall armyworm (Spodoptera frugiperda) and tested how particular members present in the gut community influence interactions with plant defenses that can alter PM permeability. We observed interactions between gut bacteria with plant resistance. Axenic insects grew more, but displayed lower immune-based responses compared to those possessing Enterococcus, Klebsiella, and Enterobacter isolates from field-collected larvae. While gut bacteria reduced performance of larvae fed on plants, none of the isolates produced mortality when injected directly into the hemocoel. Our results strongly suggest that plant physical and chemical defenses not only act directly upon the insect, but also have some interplay with the herbivore’s microbiome. Combined direct and indirect, microbe-mediated assaults by maize defenses on the fall armyworm on the insect digestive and immune system reduced growth and elevated mortality in these insects. These results imply that plant-insect interactions should be considered in the context of potential mediation by the insect gut microbiome

Fall armyworm immune responses to bacteria and plant defenses

phenoloxidase, pro-phenoloxidase, and hemocyte responses of fall armywor