Hypersensitive response-like lesions 1 codes for AtPPT1 and regulates accumulation of ROS and defense against bacterial pathogen Pseudomonas syringae in Arabidopsis thaliana

Aims: Plants employ both basal and resistance gene (R gene)-mediated defenses in response to pathogens. Reactive oxygen species (ROS) are widely reported to play a central role in both basal and R gene-mediated defense; however, the nature of ROS has been less well established for basal defense. In addition, spatial distribution of redox moieties and mechanisms of plant responses during basal defense are poorly understood. We investigated redox signaling in Arabidopsis thaliana in response to virulent bacterial pathogen, focusing on the role of the mitochondria in balancing energy demands against generation of physiologically relevant ROS. Results: Positional cloning of an Arabidopsis lesion mimic mutant identified a polyprenyl transferase involved in the biosynthesis of Coenzyme Q₁₀ (CoQ), which leads to novel insights into physiological ROS levels and their role in basal resistance. Gain- and loss-of-function studies identified Coenzyme Q₁₀ redox state to be a key determinant of ROS levels. These Coenzyme Q₁₀ redox state-mediated ROS levels had a direct bearing on both response against pathogen and ability to thrive in high oxidative stress environments. Innovation: We demonstrate that Coenzyme Q₁₀ redox state generates an ROS threshold for a successful basal resistance response. Perturbation of the Coenzyme Q₁₀ redox state has the potential to disrupt plant defense responses against bacterial pathogens. Conclusions: Coenzyme Q₁₀ redox state is a key regulator of Arabidopsis basal resistance against bacterial pathogens. Antioxid. Redox Signal. 22, 785-796.