DEFINITION OF CONSTITUTIVE GENE-EXPRESSION IN PLANTS - THE TRANSLATION INITIATION-FACTOR 4A GENE AS A MODEL

The NeIF-4A10 gene belongs to a family of at least ten genes, all of w hich encode closely related isoforms of translation initiation factor 4A. The promoter region of NeIF-4A10 was sequenced, and four mRNA 5' e nds were determined. Deletions containing 2750, 689 and 188 bp of untr anscribed upstream DNA were fused to the GUS reporter gene and introdu ced into transgenic tobacco. The three constructs mediated GUS express ion in all cells of the leaf, stem and shoot apical meristem. Control experiments using in situ hybridization and tissue printing indicated that the observed GUS expression matches the expression patterns of Ne IF-4A mRNA and protein. This detailed analysis at the level of mRNA, p rotein and reporter gene expression shows that NeIF-4A10 is an ideal c onstitutively expressed control gene. We argue that inclusion of such a control gene in experiments dealing with specifically expressed gene s is in many cases essential for the correct interpretation of observe d expression patterns.