The maize zein gene zE19 contains two distinct promoters which are independently activated in endosperm and anthers of transgenic Petunia plants.

The activity, tissue specificity and temporal expression of the tandem promoter region preceding a maize zein gene (zE19, encoding a 19 kDa zein protein) were tested in transgenic Petunia plants. To simplify the analysis, the tandem promoter as well as each of the two separate promoter regions were fused to the beta-glucuronidase (GUS) reporter gene. All of the three constructs directed the synthesis of GUS in the endosperm of transformed seeds indicating that both separate promoters are independently activated and show the same tissue and cell type specificity observed for zein genes in maize. The kinetics of accumulation and the localization of GUS activity are not coordinated with those of Petunia endogenous seed storage proteins during the development of transformed seeds. Unexpectedly, we detected high levels of GUS activity in anthers of transformed Petunia plants for all three constructs. This appears to reflect the expression pattern of zein genes in maize, since we detect zein transcripts in anthers. Finally, we discuss the possible origin and function of the tandem promoter arrangement on the basis of these data.