Quantitative regulation of the Flaveria Me1 gene is controlled by the 3 '-untranslated region and sequences near the amino terminus

The Me1 gene of Flaveria bidentis codes for the C-4 isoform of NADP malic e nzyme, which accumulates to a high-level only in bundle sheath cells. Previ ous experiments demonstrated that sequences at the 5' end of the gene contr ol cell specificity whereas sequences at the 3' end are necessary for high- level expression. To localize quantitative regulator sequences, we have ana lysed a series of Me1 3' deletion constructs fused to the gusA reporter gen e. We show that sequences within the 3'-untranslated region (3'-UTR) contro l quantitative levels of expression. Analysis of 5' promoter fusions demons trated that high-level expression also requires sequences within the N-term inal coding region of the gene, suggesting possible interactions between th e 3'-UTR and 5' coding regions. Cell-specific regulatory sequences are loca ted in a different part of the 5' end of the gene, between 1023 bp upstream of the transcription start and the start of translation.