The chloroplast FBPase gene of wheat: structure and expression of the promoter in photosynthetic and meristematic cells of transgenic tobacco plants.

A gene encoding chloroplast fructose-1,6-bisphosphatase (FBPase) was isolated from a genomic library of wheat DNA. Comparison of the gene sequence obtained with that of a wheat cDNA clone revealed the presence of three introns, each less than 100 bases in length. One of these introns lies in a region that may be involved in the light activation of FBPase catalytic activity. Chimeric gene constructs comprising 1673 bp of the upstream FBPase promoter region in a transcriptional fusion to the beta-glucuronidase (GUS) reporter gene were used to investigate expression in transgenic tobacco plants. Histochemical localization of GUS activity revealed high levels of expression driven by the FBPase promoter sequences in photosynthetically active tissues and, unexpectedly, also in the meristematic regions of shoots, lateral buds and roots. The biological significance of FBPase expression in meristematic regions is not yet clear but this pattern of expression may be explained by the presence in the FBPase promoter of a short DNA sequence motif which is also found in the CaMV 35S viral promoter.