Plant Defense against Necrotrophic Pathogens

Abstract

Necrotrophic pathogenic bacteria, fungi and oomycetes are widely distributed and are responsible for significant crop losses. Host plants deploy different defense mechanisms and appropriate immune responses to defend them against these pathogens. Regardless of the pathogen's lifestyle, infection activates plant immune responses either through Pathogen/Microbe Associated Molecular Pattern (P/MAMP) or through Effector Triggered Immunity (ETI). However, as R-genes are not usually associated with resistance to necrotrophs, resistance is largely dependent on the balanced interplay between crucial phytohormones in complex signaling pathways involving jasmonic acid (JA), ethylene, salicylic acid (SA) and abscisic acid (ABA). An increase in salicylic acid levels enhances susceptibility to necrotrophic pathogens but promotes resistance to hemibiotrophs, whereas a deficiency in SA or SA signaling has either no significant impact or affects resistance only at the primary infection site. The same fashion is observed for JA signaling system that appears to elicit resistance against diseases caused by necrotrophic pathogens and can trigger systemic immunity conferring resistance against them. On the other hand, ABA can play a positive or negative role in plant defense responses to necrotrophs as ABA-mediated defense responses are dependent on specific plant-pathogen interactions. Understanding plant immune response against necrotrophic pathogens may lead to the development of resistant or tolerant crop cultivars.

A rice gene encoding glycosyl hydrolase plays contrasting roles in immunity depending on the type of pathogens

“…Activation of PTI leads to the activation of specific hormone‐regulated signalling pathways (Verhage et al, 2010). Changes in defence‐related gene expression caused by the loss of MORE1 are consistent with the well‐established role of the SA and JA signalling pathways in regulating defence against hemibiotrophic/biotrophic and necrotrophic pathogens, respectively (Aerts et al, 2020; Berens et al, 2017; Ghozlan et al, 2020; Glazebrook, 2005). In more1 (Figure 3a) and osmore1a (Figure 7c and Table ), transcript levels of the genes controlled by SA were induced, while those under the control of JA were suppressed.…”

Quantification of shedding of leaves in yerba mate and determination of associated hormonal levels

“…Thus, ABA could have an intermediary role in organ abscission (Aurelio et al, 2000;Agustí et al, 2007). On the other hand, ABA ABA biosynthesis is required for efficient disease resistance against necrotrophic fungal pathogens (Ton and Mauch-Mani, 2004;García-Andrade et al, 2011); in particular its role in plant defense responses to necrotrophs can be positive or negative as well as dependent of the specific plant-pathogen interactions (Ghozlan et al, 2020). In this sense, ABA seems to play positive roles during the early events of infection by affecting stomatal closure and deposition of callose and the negative roles usually at later stages that include suppressing ROS accumulation and SA induction (Asselbergh et al, 2008;Ton et al, 2009).…”

Biological Control of Plant Pathogens: A Global Perspective

“…This action requires a signalization of the pathway of phytohormones, phytoalexins, and defense enzymes such as phenylalanine ammonia-lyase, chitinase, PR-proteins, and phenolic compounds ( Figure 3 ) [ 74 , 133 ]. Plant defense signaling molecules include salicylic acid involved in defense against biotrophic pathogens and systemic acquired resistance, as well as jasmonic acid and ethylene, both of which are generally considered necessary for defense against necrotrophic pathogens and are beneficial in plant–microbe interactions [ 134 , 135 ]. Inoculation of the plants with specific PGPRs elicits a phenomenon referred to as induced systemic resistance (ISR; Van Loon et al [ 136 ]).…”