CATALASE2 functions for seedling postgerminative growth by scavenging H 2 O 2 and stimulating ACX2/3 activity in Arabidopsis.

Increased fatty acid β-oxidation is essential for early postgerminative growth in seedlings, but high levels of H2 O2 produced by β-oxidation can induce oxidative stress. Whether and how catalase (CAT) functions in fine-tuning H2 O2 homeostasis during seedling growth remain unclear. Here, we report that CAT2 functions in early seedling growth. Compared to the wild type, the cat2-1 mutant, with elevated H2 O2 levels, exhibited reduced root elongation on sucrose (Suc)-free medium, mimicking soils without exogenous sugar supply. Treatment with the H2 O2 scavenger potassium iodide rescued the mutant phenotype of cat2-1. In contrast to the wild type, the cat2-1 mutant was insensitive to the CAT inhibitor 3-amino-1,2,4-triazole in terms of root elongation when grown on Suc-free medium, suggesting that CAT2 modulates early seedling growth by altering H2 O2 accumulation. Furthermore, like cat2-1, the acyl-CoA oxidase (ACX) double mutant acx2-1 acx3-6 showed repressed root elongation, suggesting that CAT2 functions in early seedling growth by regulating ACX activity, as this activity was inhibited in cat2-1. Indeed, decreased ACX activity and short root of cat2-1 seedlings grown on Suc-free medium were rescued by overexpressing ACX3. Together, these findings suggest that CAT2 functions in early seedling growth by scavenging H2 O2 and stimulating ACX2/3 activity.