Identifying Photoprotection Mutants in Arabidopsis thaliana

Plants have a range of mechanisms to protect against oxidative damage induced by excess light and environmental stress. One of these processes consists of the detoxification of reactive oxygen species by the ascorbate peroxidase (APX) family of enzymes, which convert H₂ O₂ into H₂ O. Two of the genes encoding APX in Arabidopsis are induced by high light, namely APX1 and APX2. We have applied a genetic approach to understanding the mechanisms of photoprotection, using APX2 as an indicator of oxidative stress. Transgenic plants containing the reporter gene luciferase linked to the APX2 promoter were EMS mutagenized and kindly provided to us by Mullineaux and colleagues (1 ,2 ). We have screened this mutagenized seed to identify mutants with aberrant photoprotection, based on altered luminescence resulting from altered luciferase activity. Here we describe the screen and steps involved in the identification of the mutations in an effort to identify novel photoprotective genes and products.