Reactive oxygen species dosage in Arabidopsis chloroplasts can improve resistance towards Colletotrichum higginsianum by the induction of WRKY33

Abstract

Summary Arabidopsis plants overexpressing glycolate oxidase in chloroplasts (GO5) and loss‐of‐function mutants of the major peroxisomal catalase isoform, cat2‐2, produce increased hydrogen peroxide (H2O2) amounts from the respective organelles when subjected to photorespiratory conditions like increased light intensity. Here, we have investigated if and how the signaling processes triggered by H2O2 production in response to shifts in environmental conditions and the concomitant induction of indole phytoalexin biosynthesis in GO5 affect susceptibility towards the hemibiotrophic fungus Colletotrichum higginsianum. Combining histological, biochemical, and molecular assays, we found that the accumulation of the phytoalexin camalexin was comparable between GO genotypes and cat2‐2 in the absence of pathogen. Compared with wild‐type, GO5 showed improved resistance after light‐shift‐mediated production of H2O2, whereas cat2‐2 became more susceptible and allowed significantly more pathogen entry. Unlike GO5, cat2‐2 suffered from severe oxidative stress after light shifts, as indicated by glutathione pool size and oxidation state. We discuss a connection between elevated oxidative stress and dampened induction of salicylic acid mediated defense in cat2‐2. Genetic analyses demonstrated that induced resistance of GO5 is dependent on WRKY33, but not on camalexin production. We propose that indole carbonyl nitriles might play a role in defense against C. higginsianum.

Local and Systemic Changes in Photosynthetic Parameters and Antioxidant Activity in Cucumber Challenged with Pseudomonas syringae pv lachrymans

“…In chloroplasts of the 3rd leaves, the induction of the ascorbate-glutathione cycle enzymes at 5 and 7 dai potentially curtails the pathogen-induced oxidative burden during the advanced stage of infection, when limitations of CO 2 supply mAy cause chloroplasts to produce ROS via O 2 photoreduction. Their earlier activity decreases promoting H 2 O 2 accumulation, fit into the concept of the critical role of chloroplastic ROS burst, particularly signals generated by H 2 O 2 in chloroplasts, in inducing immune responses [57,58]. However, this could not be the case in our study as at that time the chloroplast redox environment appeared to be shifted toward the reduced state due to increased AA content and AA/DHA redox ratio.…”

A novel pathogenicity determinant hijacks maize catalase 1 to enhance viral multiplication and infection

“…For instance, Nicotiana tabacum with CAT1 overexpression inhibited chilli veinal mottle virus (ChiVMV) accumulation while CAT1 knockout mutant became more susceptible (Yang et al ., 2020). In addition, catalase mutant ( cat2‐2 ) was demonstrated to increase the susceptibility of Arabidopsis to the hemibiotrophic fungus Colletotrichum higginsianum (Schmidt et al ., 2020). In view of the important roles of catalase in plant defence, it appears that this protein is a common target of various plant pathogens.…”

Redox responses of Arabidopsis thaliana to the green peach aphid, Myzus persicae

“…In contrast, there are other plant-pathogen interactions in which effective host plant defences rely on peroxisomal antioxidants rather than pro-oxidants. Inhibition of CATALASE 2 (CAT2), which detoxifies H 2 O 2 in the peroxisomes, increases susceptibility to the fungus Colletotrichum higginsianum and the oomycete Phytophthora capsici (Schmidt et al, 2020;Zhang et al, 2015), possibly because catalase activity negatively regulates salicylate-dependent hypersensitive cell death (Li et al, 2013). Similar to these hemibiotrophic pathogens, the green peach aphid on Arabidopsis also displays enhanced fecundity on a cat2 null mutant compared with wild-type controls (Rasool et al, 2020), suggesting that ROS accumulation in the peroxisome could potentially facilitate aphid infestation.…”