The use of activated charcoal to remove endogenous fluorescence from tobacco callus extracts

The enzyme β-glucuronidase (GUS) is the most widely used reporter gene for studying promoter activity in transgenic plants. In this communication we report the use of activated charcoal to remove the background fluorescence frequently observed in fluorometric GUS assays. This endogenous fluorescence is usually removed by spinning the crude extract through a spin column, which is both expensive and time consuming. We have found that the same results may be obtained by mixing an aliquot of the extract with activated charcoal. This technique is reproducible, inexpensive and very rapid. The specific activity of the GUS is unchanged by this procedure and the extent of protein loss is comparable in both purification procedures.