Protein phosphatase 2A ( PP2A) regulatory subunit B′γ interacts with cytoplasmic ACONITASE 3 and modulates the abundance of AOX1A and AOX1D in Arabidopsis thaliana.

Organellar reactive oxygen species ( ROS) signalling is a key mechanism that promotes the onset of defensive measures in stress-exposed plants. The underlying molecular mechanisms and feedback regulation loops, however, still remain poorly understood. Our previous work has shown that a specific regulatory B′γ subunit of protein phosphatase 2A ( PP2A) is required to control organellar ROS signalling and associated metabolic adjustments in Arabidopsis thaliana. Here, we addressed the mechanisms through which PP2A-B′γ impacts on organellar metabolic crosstalk and ROS homeostasis in leaves., Genetic, biochemical and pharmacological approaches, together with a combination of data-dependent acquisition ( DDA) and selected reaction monitoring ( SRM) MS techniques, were utilized to assess PP2A-B′γ-dependent adjustments in Arabidopsis thaliana., We show that PP2A-B'γ physically interacts with the cytoplasmic form of aconitase, a central metabolic enzyme functionally connected with mitochondrial respiration, oxidative stress responses and regulation of cell death in plants. Furthermore, PP2A-B'γ impacts ROS homeostasis by controlling the abundance of specific alternative oxidase isoforms, AOX1A and AOX1D, in leaf mitochondria., We conclude that PP2A-B'γ-dependent regulatory actions modulate the functional status of metabolic enzymes that essentially contribute to intracellular ROS signalling and metabolic homeostasis in plants. [ABSTRACT FROM AUTHOR]