Herbivore exploits orally secreted bacteria to suppress plant defenses

Abstract

Significance The role of herbivore-associated microbes in modifying plant defenses has received scant attention. The Colorado potato beetle secretes symbiotic bacteria to wounds to manipulate plant defenses. The bacteria elicit salicylic acid (SA)-regulated defenses, and because SA signaling often negatively cross-talks with jasmonate signaling, plants are unable to fully activate their jasmonate-mediated resistance against the herbivore. From the plants’ perspective, they recognize herbivores not as such, but as microbial threats. We identified the specific bacteria from the beetle secretions and also characterized one of the bacterial effectors responsible for defense suppression. This clever, deceptive strategy for suppressing defenses has not been previously documented. Our results add a significant, unique concept to plant–insect interactions and how herbivores hijack plant defense signaling.

Arabidopsis MYC Transcription Factors Are the Target of Hormonal Salicylic Acid/Jasmonic Acid Cross Talk in Response to Pieris brassicae Egg Extract

“…Symbionts belonging to three genera activated SA accumulation and expression of SA-regulated genes while suppressing JA responses. Antibiotic-treated larvae did not cause such response and gained less weight on tomato plants (Chung et al, 2013). Our finding that insect egg-induced activation of the SA pathway leads to diminished MYC protein levels and therefore suppresses JA-dependent defense gene expression provides a molecular mechanism that may be conserved between all these examples.…”

Third-party mutualists have contrasting effects on host invasion under the enemy-release and biotic-resistance hypotheses

“…We could change our input code to explore the effect on plant fitness if a plant simultaneously encounters a novel pathogen while interacting with an herbivore. If we were interested in exploring the evolution of the interaction between the Colorado potato beetle Leptinotarsa decemlineata and its microbial symbionts, we can model herbivore-associated microbes and how these decrease plant fitness (Chung et al 2013). It can be used with other systems to explore different trophic levels as well.…”

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

“…We have only begun to understand how endophytic symbionts in the insect gut can alter plant defenses (Chung et al, 2013). Similarly, little is known about herbivore frass-induced defenses in plants Schwartzberg and Tumlinson 2014).…”

“…4b). We also measured transcript abundance of a SAinduced pathogen defense gene pathogenesis related protein 1-p4 [Sl-PR1-(P4)] in response to frass protein on leaves (Chung et al 2013). Transcript abundance of Sl-PR1-(P4) was same in both frass-and buffer-treated tomato leaves at all time points tested (Fig.…”