Induced Resistance – Orchestrating Defence Mechanisms through Crosstalk and Priming

Abstract

Abstract:In nature, plants interact with a wide range of microbial pathogens and herbivorous insects. During the evolutionary arms race between plants and their attackers, primary and secondary immune responses evolved to recognise common or highly specialised features of the attacker encountered, resulting in sophisticated mechanisms of induced defence. Induced resistance mechanisms are characterised by a broad-spectrum effectiveness and often act systemically in plant parts distant from the site of primary attack, thereby protecting the plant against subsequent invaders. Plant hormones are key players in the regulation of the defence signalling pathways involved. Because induced defence responses entail ecological fitness costs, plants must possess elaborate regulatory mechanisms that efficiently coordinate the activation of attacker-specific defences so that fitness costs are minimised while optimal resistance is attained. A major focus in plant defence signalling research is to uncover key mechanisms by which plants tailor their responses to different attackers, and to investigate how plants cope with simultaneous interactions with multiple aggressors. Pathway crosstalk and priming for enhanced defence emerged as important regulatory mechanisms that enhance the efficiency of the plant's inducible defence arsenal. Here, we review the current knowledge on the signalling cascades involved in different types of induced pathogen and insect resistance, and the regulatory mechanisms by which plants are able to orchestrate their inducible defences in a cost-effective manner.

Priming with a Seaweed Extract Strongly Improves Drought Tolerance in Arabidopsis

“…SF is a concentrated alkaline extract of the seaweed A. nodosum, which contains a range of unique carbohydrates such as fucoidan, alginate, and laminarin, as well as proteins and minerals [ 14 ]. Studies in plants have shown that certain chemicals and the exposure to mild abiotic cues can trigger a process known as “priming” to induce robust and efficient defense mechanisms upon a subsequent stress challenge [ 76 , 77 ]. This study was based on the hypothesis that pretreating plants with the A. nodosum extract SF can prime and induce tolerance to drought stress.…”

Proteome Analysis of Nicotiana tabacum Cells following Isonitrosoacetophenone Treatment Reveals Defence-Related Responses Associated with Priming

“…Both of the aforementioned proteins have been shown to be induced under application of the defence-associated phytohormone abscisic acid (ABA) [25]. Furthermore, these proteins, in conjunction with the UDP-linked proteins, strongly suggest INAP-induced cell wall reinforcement and maintenance occurring at around 8 h, a large contributor to the up-regulation seen in Figure 3A and 3B, thus supporting a primed state by enhancement of basal resistance [3]. Conversely, superoxide dismutase (Cu-Zn), polygalacturonase inhibiting protein (PGIP) and K4ASK1_SOLLC (callose synthase 9-like) (Table 1) were found to be only differentially regulated (down-regulated) in the 16 h treated sample.…”

“…Successful host survival following stress exposure results in an enhanced basal resistance capacity, allowing for a more rapid response to future attacks through broad spectrum defences, primarily systemic acquired resistance (SAR) and induced systemic resistance (ISR) [3][4][5]. These defences may be similarly triggered by various chemical agents.…”

“…These defences may be similarly triggered by various chemical agents. Examples of these include β-aminobutyric acid (BABA) as well as salicylic acid (SA) and its functional analogues 2,6-dichloro-isonicotinic acid (INA) and benzo 1,2,3-thiadiazole (BTH) [3,4]. Utilisation of chemical-based elicitation of plant defences is a part of the priming phenomenon, defined as the pre-exposure of host plants to defence-inducing stimuli, mimicking biotic and abiotic stressors and allowing plant adaptation in launching defence responses more rapidly [6].…”

Intraspecific variation in plant‐associated herbivore communities is phylogenetically structured in Brassicaceae

“…Plants evolved inducible defences that are activated upon recognition of attack to save metabolic costs associated with production and maintenance of defence when herbivores are absent (Meldau et al, 2012 ). Plasticity in defence also allows plants to tailor defences to specific antagonists and to integrate responses to multiple attackers (Thaler et al, 2012 ; Van der Ent et al, 2018 ). Variation in interactions with herbivores that are not predominantly structured by plant functional traits may impact the evolution of such plastic defence strategies.…”