Digestive activity and organic compounds of Nezara viridula watery saliva induce defensive soybean seed responses

Abstract

The stink bug Nezara viridula is one of the most threatening pests for agriculture in North and South America, and its oral secretion may be responsible for the damage it causes in soybean (Glycine max) crop. The high level of injury to seeds caused by pentatomids is related to their feeding behavior, morphology of mouth parts, and saliva, though information on the specific composition of the oral secretion is scarce. Field studies were conducted to evaluate the biochemical damage produced by herbivory to developing soybean seeds. We measured metabolites and proteins to profile the insect saliva in order to understand the dynamics of soybean-herbivore interactions. We describe the mouth parts of N. viridula and the presence of metabolites, proteins and active enzymes in the watery saliva that could be involved in seed cell wall modification, thus triggering plant defenses against herbivory. We did not detect proteins from bacteria, yeasts, or soybean in the oral secretion after feeding. These results suggest that the digestive activity and organic compounds of watery saliva may elicit a plant self-protection response. This study adds to our understanding of stink bug saliva plasticity and its role in the struggle against soybean defenses.

Plant volatiles guide the new pest Dichelops furcatus to feed on corn seedlings

“…Herbivore saliva can modulate VOCs emission in an intra‐specific way which might depend on corn hybrids genetic background 19 . The watery saliva of Stink bugs is one of the first fluids to come in contact with the plant during herbivory, and its possible effectors on defensive hormonal pathways have been recently studied 2,3,20 …”

“…Plant recognition of stink bug damage leads to rapid transcription and activation of MAPK signaling pathways that induce JA/ET and SA‐regulated defenses 3 . Although it is well known that induction of JA increases VOCs emission, 40 the role of the other hormones in fine‐tuning regulation of qualitative VOCs emission is not completely understood.…”

“…In temperate and neotropical regions of South America, the generalist stink bug Dichelops furcatus F. has recently become a new pest of corn at seedling stage. Stink bugs feed on plants by inserting toxic saliva and sucking fluids from damaged tissues 2,3 . Adults of D. furcatus feed on seedlings by inserting their stylets near the coleoptile, mechanically and/or chemically macerating plant tissues.…”

“…VOCs emission is regulated by different pathways that allow plants to perceive herbivore attack through mechanical damage and elicitors present in oral secretions 3,18‐20 . Stink bug‐attacked plants can respond with distinctive signaling pathways, by triggering a series of fine‐tuning signaling.…”

“…However, the feeding strategy of stink bugs provokes a different kind of tissue damage in comparison with those triggered by aphids or chewing insects. Stink bugs use stylets to pierce and inject saliva with digestive activity and organic compounds that induced plant responses 3 . Whereas corn seedlings treated with regurgitant of lepidopterans larvae increased JA, decreased SA levels and trigger VOCs emission in corn seedlings, 16 effectors present in aphid saliva have opposite effects, triggering SA pathway 27 and reminding VOCs constitutive levels 24 .…”