Necrotrophic Exploitation and Subversion of Plant Defense: A Lifestyle or Just a Phase, and Implications in Breeding Resistance

Abstract

Breeding disease-resistant plants is a critical, environmentally friendly component of any strategy to sustainably feed and clothe the 9.8 billion people expected to live on Earth by 2050. Here, I review current literature detailing plant defense responses as they relate to diverse biological outcomes; disease resistance, susceptibility, and establishment of mutualistic plant–microbial relationships. Of particular interest is the degree to which these outcomes are a function of plant-associated microorganisms’ lifestyles; biotrophic, hemibiotrophic, necrotrophic, or mutualistic. For the sake of brevity, necrotrophic pathogens and the necrotrophic phase of pathogenicity are emphasized in this review, with special attention given to the host-specific pathogens that exploit defense. Defense responses related to generalist necrotrophs and mutualists are discussed in the context of excellent reviews by others. In addition, host evolutionary trade-offs of disease resistance with other desirable traits are considered in the context of breeding for durable disease resistance.

Iron homeostasis and plant immune responses: Recent insights and translational implications

“…This is because biotrophs depend on living plant cells for nutrients, whereas necrotrophs purposefully trig-ger host cell death. Indeed, some necrotrophs activate ETI as a virulence strategy (30). These differing pathogen lifestyles hold important implications for predicting whether crop biofortification could impact disease resistance and will be discussed below.…”

LsGRP1, a class II glycine‐rich protein of Lilium, confers plant resistance via mediating innate immune activation and inducing fungal programmed cell death

“…Small oxidative bursts act as secondary messengers of various signalling pathways, including defence pathways, and are often important for the initiation and spread of HR, a unique PCD in plants. However, excess ROS accumulation can guide plant cells to commit suicide through apoptosis, which is a type of PCD favoured by certain necrotrophic pathogens feeding on dead host cells, such as B. cinerea (Veloso and van Kan, 2018;Balint-Kurti, 2019;Lorang, 2019). In addition, B. elliptica secretion-induced lily cell death belongs to apoptosis, which is required for the subsequent fungal infection (van Baarlen et al, 2004).…”

“…ETI is regarded as an accelerated and amplified PTI response with shared signalling mechanisms and often leads to a hypersensitive response (HR) and systemic acquired resistance, a form of induced resistance to prevent secondary infections (Peng et al, 2018;Zhang et al, 2018;Noman et al, 2019). HR is a unique plant programmed cell death (PCD), occurring at or around pathogen penetration sites, capable of preventing infection but beneficial for certain necrotrophic pathogens (Balint-Kurti, 2019;Lorang, 2019). Pathogen recognition alters the expression of approximately 20% of total genes in a single plant species, and a proper plant transcriptional reprogramming is critical for orchestrating effective defence responses and minimizing fitness cost (Bigeard et al, 2015;Zhang et al, 2018).…”

Expression of Thioredoxin/Thioredoxin Reductase System Genes in Aphid-Challenged Maize Seedlings

“…Major biological functions of plant thioredoxins include posttranslational redox regulation of a wide array of proteins, participation in antioxidative scavenging and signaling networks, overcoming oxidative damages to macromolecules as well as intercellular communication [ 6 , 25 , 26 ]. Several isoforms of thioredoxins ( f -, m -, x -, y -, and z -type) have been identified in chloroplasts, and their main biological role is associated with modulation of activity of target proteins involved in photosynthesis process [ 27 , 28 ].…”