One of the most important considerations in the expression of heterologous proteins in plants is the choice of promoter. The study of promoter activity is simplified in the majority of cases by the use of a readily detectable reporter gene. Indeed, reporter genes can also be used to aid the isolation of promoters, through the transformation of plants with a promoterless reporter gene construct. Activation of the reporter gene will then only occur if the gene is inserted adjacent to a native promoter (1).