CATALASE2 is positively involved in Arabidopsis thaliana root development

Catalase (CAT) is a key enzyme in plant development and in the regulation of oxidative stress arising from the uncontrolled overproduction of reactive oxygen (ROS) in particular. Despite its well-established role in aerial organs, CAT functions in the root system require investigation. 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 in lateral root (LR) development. Primary root (PR) and LR development were analysed in cat2-1 through morpho-cyto-histological investigations, oxidative assays, and metabolomic analyses. To further investigate the CAT2 role in the root system architecture, we exposed cat2-1 to oxidative stress by using CdSO4 . 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. The cat2-1 root alterations were associated with an accumulation of trans-zeatin-type cytokinin and with changes in ROS homeostasis. Loss of CAT2 function exacerbated some of the Cd-related alterations, particularly the disorganisation of cell division and differentiation patterns within the root meristems, and ROS accumulation, further 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.