Abstract
Peroxidases are enzymes that catalyze the reduction of hydrogen peroxide, thus minimizing cell injury and modulating signaling pathways as response to this reactive oxygen species. Using a phylogenetic approach, we previously identified a new peroxidase family composed of a small subset of ascorbate peroxidase (APx) homologs with distinguished features, which we named ascorbate peroxidase-related (APx-R). In this study, we showed that APx-R is an ascorbate-independent heme peroxidase. Despite being annotated as a cytosolic protein in public databases, transient expression of AtAPx-R-YFP in Arabidopsis thaliana protoplasts and stable overexpression in plants showed that the protein is targeted to plastids. To characterize APx-R participation in the antioxidant metabolism, we analyzed loss-of-function mutants and AtAPx-R overexpressing lines. Molecular analysis showed that glutathione peroxidase 7 (GPx07) is specifically induced to compensate the absence of APx-R. APx-R overexpressing lines display faster germination rates, further confirming the involvement of APx-R in seed germination. The constitutive overexpression of AtAPx-R-YFP unraveled the existence of a post-translational mechanism that eliminates APx-R from most tissues, in a process coordinated with photomorphogenesis. Our results show a direct role of APx-R during germinative and post-germinative development associated with etioplasts differentiation.
Highlights
Peroxidases are heme-containing enzymes present in bacteria, fungi, plants, and animals, which catalyze the reduction of hydrogen peroxide and the oxidation of a wide variety of organic and inorganic substrates [1]
By transient and constitutive overexpression in plant cells, we demonstrated that ascorbate peroxidase (APx)-R is targeted to chloroplasts and undergoes a post-translational mechanism to prevent its accumulation in green tissues during plant development in a process coordinated with photomorphogenesis
ascorbate peroxidase-related (APx-R) Is a Peroxidase that Does not Use as Substrate at 430 and 470 nm, respectively
Summary
Peroxidases are heme-containing enzymes present in bacteria, fungi, plants, and animals, which catalyze the reduction of hydrogen peroxide and the oxidation of a wide variety of organic and inorganic substrates [1]. Based on sequence similarity and protein structure, they are divided into the peroxidase-cyclooxygenase and the non-animal peroxidase superfamilies [2,3,4] The latter includes twelve families of evolutionarily related enzymes found in bacteria, algae, fungi, and/or plants, which are further categorized into three large classes [2,5]. It is well-accepted that members of the non-animal peroxidase superfamily share a prokaryotic origin, and that the emergence of each family is tightly associated with processes related to mitochondria and chloroplast acquisition and countless duplication events throughout genomes’ evolution [6]. The non-animal superfamily is primarily represented by class III secretory peroxidases and class I intracellular peroxidases, which depend on ascorbate
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