Peroxisomal CATALASE2 positively regulates Arabidopsis lateral root development

Catalase (CAT) is one of the key enzymes in plant development and in the regulation of nitro-oxidative stress associated with the uncontrolled overproduction of reactive oxygen (ROS) and nitrogen species (RNS). Despite its well-established role in aerial organs, CAT functions in the root system remain underexplored. Using Arabidopsis thaliana cat2–1, defective in CAT2 and exhibiting reduced CAT activity, we demonstrated that CAT2 is directly involved in defining root architecture, particularly lateral root (LR) development under optimal growth conditions. Primary root (PR) and LR development were analysed in cat2–1 through morpho-cyto-histological investigations, nitro-oxidative assays, and metabolomic analyses. To further investigate CAT2’s role in root architecture, we exposed cat2–1 to nitro-oxidative stress using 60 μM cadmium sulphate (CdSO4). Results show that CAT2 is the main CAT isozyme in Arabidopsis root system. cat2–1 showed inhibition of LR development and PR elongation, exacerbated by Cd. These defects were highlighted by cyto-histological analyses, revealing alterations in the division/differentiation patterns of pericycle cells competent for LR initiation as well as in meristematic cells of PR and LRs. Cat2–1 root alterations were associated with an accumulation of trans-zeatin-type cytokinin and with changes in ROS- and, to a lesser extent, RNS-homeostasis. Loss of CAT2 function exacerbated some of the Cd-related alterations, particularly the disorganisation of cell division and differentiation patterns within root meristems, and ROS accumulation, supporting a positive role of CAT2 in root architecture. Our results demonstrate a new role for CAT2 per se in Arabidopsis root system development, beyond its involvement in regulating stress response processes.