Signal Signature and Transcriptome Changes of Arabidopsis During Pathogen and Insect Attack

Abstract

Plant defenses against pathogens and insects are regulated differentially by cross-communicating signaling pathways in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) play key roles. To understand how plants integrate pathogen-and insect-induced signals into specific defense responses, we monitored the dynamics of SA, JA, and ET signaling in Arabidopsis after attack by a set of microbial pathogens and herbivorous insects with different modes of attack. Arabidopsis plants were exposed to a pathogenic leaf bacterium (Pseudomonas syringae pv. tomato), a pathogenic leaf fungus (Alternaria brassicicola), tissuechewing caterpillars (Pieris rapae), cell-content-feeding thrips (Frankliniella occidentalis), or phloem-feeding aphids (Myzus persicae). Monitoring the signal signature in each plant-attacker combination showed that the kinetics of SA, JA, and ET production varies greatly in both quantity and timing. Analysis of global gene expression profiles demonstrated that the signal signature characteristic of each Arabidopsis-attacker combination is orchestrated into a surprisingly complex set of transcriptional alterations in which, in all cases, stress-related genes are overrepresented. Comparison of the transcript profiles revealed that consistent changes induced by pathogens and insects with very different modes of attack can show considerable overlap. Of all consistent changes induced by A. brassicicola, Pieris rapae, and F. occidentalis, more than 50% also were induced consistently by P. syringae. Notably, although these four attackers all stimulated JA biosynthesis, the majority of the changes in JA-responsive gene expression were attacker specific. All together, our study shows that SA, JA, and ET play a primary role in the orchestration of the plant's defense response, but other regulatory mechanisms, such as pathway cross-talk or additional attacker-induced signals, eventually shape the highly complex attacker-specific defense response.

Trichoderma gamsii affected herbivore feeding behaviour on Arabidopsis thaliana by modifying the leaf metabolome and phytohormones

“…In plant–insect interactions, the SA‐dependent pathway is induced by phloem‐feeding insects, whereas the JA‐dependent pathway is induced by chewing insects (Walling, 2000; De Vos et al ., 2005; Glazebrook, 2005; Pieterse et al ., 2012). Studies have reported that Trichoderma can activate both JA‐ and SA‐related signalling pathways in host plants (Segarra et al ., 2007; Contreras‐Cornejo et al ., 2011; Martinez‐Medina et al ., 2011).…”

Plant immune responses triggered by beneficial microbes

“…In most cases only weak, transient, or strictly localized defense-associated responses were elicited, which differs greatly from the massive induction of defense responses triggered during plant-pathogen interactions [39][40][41]42 ]. Transcriptome analysis of Arabidopsis expressing WCS417-ISR revealed a set of 94 genes that were differentially expressed locally in the roots [39].…”

The multifaceted role of ABA in disease resistance

“…However, the nature of the specific defense response of the plant is not determined solely by the biotrophic or necrotrophic life style of the pathogen; it also depends on additional factors, such as the timing of recognition, the activity of pathogen effectors and the type of plant tissue in which the defense is expressed. These different factors together shape the nature of the specific defense response of the plant [2]. In this context, the plant hormone abscisic acid (ABA, Box 1) has emerged as an important regulator of biotic defense responses, although its role is less straightforward than that of other defense regulatory plant hormones.…”