Molecular and physiological stages of priming: how plants prepare for environmental challenges

Abstract

Being sessile organisms, plants must respond to various challenges in the environment. The priming process consists of three clear stages. The first stage includes all the cellular changes in the absence of the challenge so-called pre-challenge priming stage. These changes are expected to be rather subtle, affecting the preparation of the plant to properly manage subsequent responses to pathogens with no major fitness costs. Most of the research that has been conducted at this stage has been dedicated to the study of changes in gene expression and protein phosphorylation. However, the metabolic changes that occur during the pre-challenge priming stage are poorly understood. The second stage affects the early to late stages of the defence response, which occurs after the interaction with a pathogen has been established. Most studies involving priming are dedicated to the molecular events that take place during this stage. Most studies have shown that defence priming is strongly hormonally regulated; however, there is also evidence of the involvement of phenolic derivative compounds and many other secondary metabolites, leading to stronger and faster plant responses. The third priming phase ranges from long lasting defence priming to trans-generational acquired resistance. Long-term metabolic transitions, that occur in the offspring of primed plants, remain to be elucidated. Here we review existing information in the literature that relates to the metabolic changes that occur during all three defence priming stages and highlight the metabolic transitions that are associated with the stimulation of priming and the characteristics of the pathogens whenever possible.

Modes of action of the protective strain Fo47 in controlling verticillium wilt of pepper

“…The second objective of this work was to study the involvement of phytohormones in the protective capacity of Fo47 against verticillium wilt of pepper, knowing that priming is a component of this capacity (Veloso & Díaz, ). The priming process consists of three stages: (i) the pre‐challenge priming stage, where the plant interacts with the priming stimulus; (ii) the challenge stage of priming, which occurs after the interaction with a pathogen has been established; and (iii) the long‐lasting and transgenerational priming (Gamir et al ., ). To determine which signalling pathways were activated during the first two priming stages, levels of some phytohormones and of their derivatives were measured in planta .…”

Starch degradation, abscisic acid and vesicular trafficking are important elements in callose priming by indole‐3‐carboxylic acid in response to Plectosphaerella cucumerina infection

“…Arabidopsis camalexin‐deficient mutants display severe symptoms when infected by A. brassicicola and B. cinerea (Ferrari et al ., ; van Wees et al ., ). However, the camalexin‐deficient mutant pad3 displays no severe symptoms with Phytophthora barassicae infection, but the double‐mutant impaired in camalexin and a mirosinase pad3‐pen2 showed disease levels similar to the double‐mutant cyp79B2‐cyp79B3 , demonstrating the importance of camalexin and indole‐glucosinolates in the tryptophan pathway to basal defence (Schlaeppi et al ., ; Gamir et al ., ,b).…”

“…An increase in the indole I3CA was detected in Arabidopsis following infection with P. cucumerina in β‐amino butyric acid (BABA)‐treated plants (Gamir et al ., ). This compound was also found to be part of a priming fingerprint of metabolites following various priming stimuli, and application of this metabolite induces resistance against fungi (Gamir et al ., ,b). However, its function must be regulatory or signalling because it has no antifungal effect on P. cucumerina .…”

“…Exogenous application of the indolic hormone IAA in barley reduces disease severity (Petti et al ., ). Other indole derivatives, such as indole‐3‐carboxyaldehyde (ICHO) and indole‐3‐carboxylic acid (ICOOH; also known as I3CA; Gamir et al ., ,b), increase upon infection (Böttcher et al ., ; Gamir et al ., ,b). Both seem to be widespread compounds that are detected not only in Brassicaceae but also in pea and Pinus sp.…”

Priming and memory of stress responses in organisms lacking a nervous system

“…Conrath, 2011;Gamir, Sánchez-Bel & Flors, 2014), herbivores (e.g. Several other terms are used to describe similar phenomena (see above, e.g.…”