Glutathione‐dependent denitrosation of GSNOR1 promotes oxidative signalling downstream of H₂O₂

Abstract

Photorespiratory hydrogen peroxide (H2O2) plays key roles in pathogenesis responses by triggering the salicylic acid (SA) pathway in Arabidopsis. However, factors linking intracellular H2O2 to activation of the SA pathway remain elusive. In this work, the catalase‐deficient Arabidopsis mutant, cat2, was exploited to elucidate the impact of S‐nitrosoglutathione reductase 1 (GSNOR1) on H2O2‐dependent signalling pathways. Introducing the gsnor1‐3 mutation into the cat2 background increased S‐nitrosothiol levels and abolished cat2‐triggered cell death, SA accumulation, and associated gene expression but had little additional effect on the major components of the ascorbate‐glutathione system or glycolate oxidase activities. Differential transcriptome profiles between gsnor1‐3 and cat2 gsnor1‐3 together with damped ROS‐triggered gene expression in cat2 gsnor1‐3 further indicated that GSNOR1 acts to mediate the SA pathway downstream of H2O2. Up‐regulation of GSNOR activity was compromised in cat2 cad2 and cat2 pad2 mutants in which glutathione accumulation was genetically prevented. Experiments with purified recombinant GSNOR revealed that the enzyme is posttranslationally regulated by direct denitrosation in a glutathione‐dependent manner. Together, our findings identify GSNOR1‐controlled nitrosation as a key factor in activation of the SA pathway by H2O2 and reveal that glutathione is required to maintain this biological function.

The Versatile Roles of Sulfur-Containing Biomolecules in Plant Defense—A Road to Disease Resistance

“…Furthermore, the GSNOR enzyme is posttranslationally activated by direct denitrosylation in a GSH-dependent manner. Activation of ICS expression leads to SA accumulation [100]. In summary, the ROS and NO formation during plant defense modulate the GSH/GSSG ratio and ultimately increase GSH levels in resistant plants.…”

“…Conversely, increased AtGSNOR1 activity reduces protein-SNO formation and positively regulates the SA induced defense responses [99]. Others have recently shown that the activation of GSNOR1 enzyme leads to the release of inhibition of ICS expression in the presence of H 2 O 2 [100]. However, when GSNOR1 is inactive, the accumulation of GSNO leads to the inhibition of ICS expression.…”

“…Interactions between ROS, NO, GSH, GSNO and GSNOR lead to increased SA accumulation in different ways during incompatible plant-pathogen interactions ( Figure 2). GSH cooperates with NO likely via unidentified (de)nitrosylation-dependent and independent pathways, to positively modulate SA-dependent gene expression such as that of ICS1 [96,98,100]. The GSNOR enzyme controls plant GSNO levels and GSH activates GSNOR enzyme activity, which catalyzes GSNO degradation to GSSG and NH 3 by using reduced β-nicotinamide adenine dinucleotide (NADH) in plant cells [101].…”

“…GSH participates in antioxidative and detoxification reactions and conducts the signaling of different plant hormones during pathogen infection. Importantly, a self-regulating circuit of H 2 O 2 , NO, glutathione and salicylic acid (SA) controls SA-mediated defense responses to bacterial and fungal infections [96,[98][99][100]. Future research should clarify whether the same/similar self-regulating signaling is also responsible for the efficiency of SA-mediated plant defense responses during viral infections.…”

Overexpressing the N‐terminus of CATALASE2 enhances plant jasmonic acid biosynthesis and resistance to necrotrophic pathogen Botrytis cinerea B05.10

“…It has been widely documented that salicylic acid (SA) plays an essential role in plant resistance to biotrophic and semibiotrophic pathogens such as the model pathogen Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) (Chen et al, 2020a;Peng et al, 2021;Zhang et al, 2020c).…”