The Arabidopsis catalase triple mutant reveals important roles of catalases and peroxisome-derived signaling in plant development.

Hydrogen peroxide (H O ) is generated in many metabolic processes. As a signaling molecule, H O plays important roles in plant growth and development, as well as environmental stress response. In Arabidopsis, there are three catalase genes, CAT1, CAT2, and CAT3. The encoded catalases are predominately peroxisomal proteins and are critical for scavenging H O . Since CAT1 and CAT3 are linked on chromosome 1, it has been almost impossible to generate cat1/3 and cat1/2/3 mutants by traditional genetic tools. In this study, we constructed cat1/3 double mutants and cat1/2/3 triple mutants by CRISPR/Cas9 to investigate the role of catalases. The cat1/2/3 triple mutants displayed severe redox disturbance and growth defects under physiological conditions compared with wild-type and the cat2/3 double mutants. Transcriptome analysis showed a more profound transcriptional response in the cat1/2/3 triple mutants compared to the cat2/3 mutants. These differentially expressed genes are involved in plant growth regulation as well as abiotic and biotic stress responses. In addition, expression of OXI1 (OXIDATIVE SIGNAL INDUCIBLE 1) and several MAPK cascade genes were changed dramatically in the catalase triple mutant, suggesting that H O produced in peroxisomes could serve as a peroxisomal retrograde signal.