Endogenous NO fluctuations in Arabidopsis leaves influence peroxisomal activities and ROS, NADPH, and H2S metabolism.

Nitric oxide (NO) is a gasotransmitter that exerts signaling functions in plants. Using 30-day-old Arabidopsis thaliana plants wild type and transgenic lines with different NO content (Atnoa1 and Atnox1/cue1), the biochemical analysis of key components in the metabolism of ROS, NADPH, NO, and H2S in leaves indicates that the imbalance of endogenous cellular NO triggered differential changes in many of the analyzed biochemical parameters including the protein profile of S-glutathionylation, S-nitrosation, tyrosine and tryptophan nitration. It was remarkable the differences observed in the antioxidant enzyme catalase and the H2O2-generating glycolate oxidase, two key peroxisomal enzymes involved in the ROS metabolism of these organelles, as well as the gene expression of the polyamine oxidase 4 (POD4) which encodes for the peroxisomal H2O2-generating POD4. Furthermore, the pattern of the H2S-generating L-cysteine desulfhydrase (LCD) isozymatic activity was also affected. These data provide new biochemical evidence of how under physiological conditions, NO can affect peroxisomal metabolism, a subcellular organelle with a very active nitro-oxidative metabolism, as well as ROS, NADPH, and H2S metabolism.