Salicylic Acid, a Plant Hormone, Suppresses Phytophagous Insect Immune Response by Interrupting HMG-Like DSP1

Abstract

Salicylic acid is a plant hormone that can mediate various plant physiological processes. Salicylic acid can bind to human high mobility group box 1 (HMGB1) and interrupt its role in mediating immune responses. Dorsal switch protein 1 (DSP1) is an insect homolog of HMGB1. In this study, a DSP1 (Se-DSP1) encoded in Spodoptera exigua, a phytophagous insect, was characterized, and its potential role in immune response was explored. Upon bacterial challenge, Se-DSP1 was localized in the nucleus and released into the hemolymph. The released Se-DSP1 could mediate both cellular and humoral immune responses by activating eicosanoid biosynthesis. Salicylic acid could bind to Se-DSP1 with a high affinity. The immune responses of S. exigua were significantly interrupted by SA feeding. Larvae reared on tomatoes with high endogenous SA levels became more susceptible to entomopathogens. Taken together, these results suggest a tritrophic defensive role of plant SA against phytophagous insects.

HMG-Like DSP1 Mediates Immune Responses of the Western Flower Thrips (Frankliniella occidentalis) Against Beauveria bassiana, a Fungal Pathogen

“…Upon the fungal infection, F. occidentalis expressed immune responses by activating DSP1, an ortholog of vertebrate HMGB1 known to act as a damage signal in response to pathogen infection in insects ( 31 ). HMGB1 is ubiquitously expressed and localized in the nucleus to bind to DNA for regulating gene expression through chromatin remodeling ( 32 ).…”

“…It can activate PLA 2 to mediate various immune responses ( 16 ). Later, Mollah et al ( 31 ) showed that DSP1 activates Toll immune signalling to PLA 2 activation via Pelle kinase in S. exigua . In F. occidentalis in our current study, DSP1 was obtained from its genome and its expression was confirmed in this study.…”

“…High conserved domain structure and sequence showed that the antibody raised against S. exigua DSP1 reacted with DSP1 of F. occidentalis and allowed us to observe DSP1 of F. occidentalis in its midgut. EMP, a secondary metabolite of a bacterial metabolite of Xenorhabdus hominickii ( 36 ), is known to inhibit the release of DSP1 in the nucleus ( 31 ). When EMP was applied together with the fungal conidia against thrips, it significantly increased the fungal virulence of B. bassiana and suppressed other immune responses including PLA 2 activation.…”

Integrated Biological Control Using a Mixture of Two Entomopathogenic Bacteria, Bacillus thuringiensis and Xenorhabdus hominickii, against Spodoptera exigua and Other Congeners

“…Recently, S. frugiperda invasions were reported in western Korea, intimidating the crop yields of rice and corn [ 29 ]. A highly virulent strain of X. hominickii was found from a comparative toxicological analysis and used to replace a previous IBC agent to control S. exigua [ 30 ]. Thus, this study was devised to develop a highly efficient IBC agent against spodopteran insect pests without hazards to humans or the environment.…”

Phytohormones Accumulation and Distribution in Shoots and Roots of Haploid, Diploid and Tetraploid Barley Seedlings Derived from Microspore Culture

“…Gibberellin (GA) controls seed germination and plays an important role in the 'green revolution' [8]. Salicylic acid (SA) and jasmonic acid (JA) act as the important signal molecules during the immune and defense responses of plants [9,10].…”