Oxalate oxidase: a novel reporter gene for monocot and dicot transformations

A wheat germin gene, with oxalate oxidase (OxO) activity, can be used as a sensitive reporter gene in both monocot and dicot transformations. Detection of H₂O₂ generated from OxO oxidation of oxalate provides simple, rapid detection of gene expression. Inexpensive substrates are required for both assays. OxO activity, could be detected histochemically in minutes, without chlorophyll clearing procedures. This assay was used to optimize transformation procedures and to track stable transgene expression in breeding populations over many generations. A simple spectrophotometric quantitative enzyme activity assay was used to select lines with various levels of transgene expression and to monitor transgene silencing phenomena. The quantitative OxO assay can also be used as an internal DNA delivery standard with a second reporter gene used in gene expression studies. The simplicity of the assay is ideal for screening large populations to identify primary transgenics, for monitoring transgene segregation in large populations in field studies and for assessing stability of transgene expression over numerous generations.