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.

中文翻译：

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拟南芥 APx-R 是一种受光形态发生调节的质体抗坏血酸独立过氧化物酶


过氧化物酶是催化过氧化氢还原的酶，从而最大限度地减少细胞损伤并调节信号通路以响应这种活性​​氧。使用系统发育方法，我们之前鉴定了一个新的过氧化物酶家族，该家族由一小部分具有显着特征的抗坏血酸过氧化物酶（APx）同源物组成，我们将其命名为抗坏血酸过氧化物酶相关（APx-R）。在这项研究中，我们证明 APx-R 是一种不依赖于抗坏血酸的血红素过氧化物酶。尽管在公共数据库中被注释为胞质蛋白， AtAPx-R-YFP在拟南芥原生质体中的瞬时表达和在植物中的稳定过表达表明该蛋白靶向质体。为了表征 APx-R 参与抗氧化代谢的特征，我们分析了功能丧失突变体和AtAPx-R过表达系。分子分析表明，谷胱甘肽过氧化物酶 7 (GPx07) 被特异性诱导以补偿 APx-R 的缺失。 APx-R 过表达株系显示出更快的发芽率，进一步证实了 APx-R 参与种子萌发。 AtAPx-R-YFP的组成型过表达揭示了翻译后机制的存在，该机制在与光形态发生协调的过程中从大多数组织中消除 APx-R。我们的结果表明 APx-R 在与黄质体分化相关的萌发和萌发后发育过程中的直接作用。