Do vacuolar peroxidases act as plant caretakers?

Plant vacuolar peroxidases catalyze the reduction of toxic H2O2 accumulated in the vacuoles by oxidizing a variety of secondary metabolites. The redundancy of peroxidases and their ability to react with a wide range of substrates have prevented the observation of a clear phenotypic effect by modifying a single gene. Here we review the correlative and partial data on vacuolar peroxidases, including evidence for genes encoding vacuolar localized peroxidases, and indications of peroxidase activity in the vacuole. Based on these data, we suggest that these enzymes are key players in the adaptation of plants to change and serve as plant caretakers. At the cellular level, peroxidases protect the plant by scavenging excess H2O2 that accumulates in the vacuoles under stressful conditions. At the tissue level, they are responsible for the last steps in the synthesis of the phytoalexins that often accumulate following pathogen attack of the plant tissue. At the whole-plant level, we suggest that peroxidases are involved in controlling the quality and quantity of light reaching the photosynthetic apparatus as plants adapt to lower light intensities. Further characterization of peroxidases, based on high-throughput genomic and metabolomic data, will help elucidate the mechanisms by which plants adapt to change.

► We suggest that the vacuolar peroxidases serve as plant caretakers.
► At the cellular level, vacuolar peroxidases scavenge excess H2O2 accumulating in the vacuoles.
► At the tissue level, vacuolar peroxidases take part in the synthesis of toxic pathogenic compounds.
► At the whole plant level, we suggest that vacuolar peroxidases control the light reaching the chloroplasts.
► Our understanding of their roles in the cell is based on incomplete and correlative data.