This invention relates to compositions and methods for reducing reactive oxygen species in plants, yeast, algae or bacteria by transforming a plant, yeast or bacteria with a heterologous polynucleotide encoding a superoxide reductase from an archaeon species. The invention also provides methods for protecting a photosynthetic reaction center, for reducing photorespiration and/or for increasing the photosynthetic efficiency of plants or cyanobacteria as well as methods for increasing tolerance to abiotic stress in plants, yeast or bacteria by transforming a plant, yeast, or bacteria with a heterologous polynucleotide encoding a archaeon superoxide reductase. Methods for delaying senescence, reducing lignin polymerization and increasing accessibility of cell wall cellulose to an enzyme in a plant by transforming the plant with a heterologous polynucleotide encoding an archaeon superoxide reductase are also provided. Additionally, transformed plants, yeast and bacteria are provided as well as products produced from the transformed plants, yeast and bacteria.
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 This invention was supported in part by funding provided under Grant No 2009-35318-05024 from the United States Department of Agriculture (USDA), and Grant No DE-AR0000207 from the United States Department of Energy (DOE). The United States government has certain rights in this invention.