Suppression of photorespiratory metabolism by low O and presence of aminooxyacetic acid induces oxidative stress in leaves.

Unlabelled: Photorespiration, an essential component of plant metabolism, was upregulated under abiotic stress conditions, such as high light or drought. One of the signals for such upregulation was the rise in reactive oxygen species (ROS). Photorespiration was expected to mitigate oxidative stress by reducing ROS levels. However, it was unclear if ROS levels would increase when photorespiration was lowered. Our goal was to examine the redox status in leaves when photorespiratory metabolism was restricted under low O (medium flushed with N gas) or by adding aminooxyacetic acid (AOA), a photorespiratory inhibitor. We examined the impact of low O and AOA in leaves of under dark, moderate, or high light. Downregulation of typical photorespiratory enzymes, including catalase (CAT), glycolate oxidase (GO), and phosphoglycolate phosphatase (PGLP) under low O or with AOA confirmed the lowering of photorespiratory metabolism. A marked increase in ROS levels (superoxide and HO) indicated the induction of oxidative stress. Thus, our results demonstrated for the first time that restricted photorespiratory conditions increased the extent of oxidative stress. We propose that photorespiration is essential to sustain normal ROS levels and optimize metabolism in cellular compartments of leaves.

Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01388-4.