Catalase import into peroxisomes in Arabidopsis

In eukaryotes, catalases are peroxisomal antioxidant enzymes that maintain cellular reactive oxygen species (ROS) homeostasis. Plant catalases lack canonical peroxisomal targeting signals (PTS), and the mechanism underlying their PEX5-dependent peroxisomal import remains poorly understood. Here, we expressed CAT2 with N- and C-terminal GFP fusions in an Arabidopsis cat2 mutant background and found that only GFP-CAT2 completely restored wild-type function despite comparable catalase activity for both CAT2-GFP and GFP-CAT2. Only GFP-CAT2 localized to peroxisomes, indicating that altered subcellular localization prevented CAT2-GFP functional complementation. Expression of CAT2-GFP in wild-type Arabidopsis and Nicotiana benthamiana revealed in vivo interaction with endogenous catalases leading to co-import into peroxisomes. Localization of YFP fused to various CAT2 C-terminal sections identified the CAT2 C-terminal five amino acids as a functional PTS1-like sequence. These findings define a minimal C-terminal targeting motif for plant catalases that is sufficient for their peroxisomal import.