GUS activities in mature transgenic seeds. GUS activity was determined by fluorometric assays on protein extracts from ten, single mature seeds derived from each homozygous plant. T9 seeds derived from a parental GUS homozygote, GPBhGN-7, and F3 seeds from two homozygotes for both GUS and GFP, GPBhGN/DhGFP-2-7 and GPBhGN/DhGFP-5-11, were used for GUS activity measurements