TITLE:
Plant Defense against Necrotrophic Pathogens
AUTHORS:
Mahmoud H. Ghozlan, Eman EL-Argawy, Serkan Tokgöz, Dilip K. Lakshman, Amitava Mitra
KEYWORDS:
Effectors, Host Immunity, Signaling, P/MAMP, ETI, Disease Resistance
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.12,
December
29,
2020
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.