PROMOTER ELEMENTS CONTROLLING DEVELOPMENTAL AND ENVIRONMENTAL-REGULATION OF A TOBACCO RIBOSOMAL-PROTEIN GENE L34

The rpL34 gene, which encodes a cytoplasmic ribosomal protein with a h igh homology to the rat 60S r-protein L34, was isolated from a genomic library of tobacco (Nicotiana tabacum L. cv. Xanthi-nc). A 1500 bp up stream promoter fragment was fused to the chloramphenicol acetyltransf erase (CAT) reporter gene or beta-glucuronidase (GUS) reporter gene an d transferred into tobacco plants by the Agrobacterium-mediated leaf d isk transformation method. Analysis of CAT activity in leaf tissues sh owed that mechanical wounding increased the rpL34 promoter activity ab out 5 times as compared to untreated controls and that the promoter ac tivity was further enhanced by plant growth regulators, 2,4-dichloroph enoxyacetic acid and benzyladenine. Histochemical GUS staining pattern s of the transgenic plants showed that the rpL34 promoter activity is high in actively growing tissues, including various meristems, floral organs, and developing fruits. A series of 5' deletion analyses of the rpL34 promoter indicated that a 50 bp region located between -179 and -129 is essential for wound, auxin and cytokinin responses. Deletion of this region reduced the promoter activity to an undetectable level. Insertion of the 50 nucleotide sequence into a minimal promoter resto red the promoter activity and the promoter strength was proportional t o the copy number of the upstream sequence. The role of TATA and CAAT box regions was studied by a series of 3' deletion analyses. A 3' dele tion up to -28 did not significantly affect the promoter strength. How ever deletion of the promoter up to 70 bp, which deleted the TATA box region, significantly reduced promoter activity. Further deletion of t he promoter up to -104, eliminating the CAAT box region, abolished the promoter activity. These results suggest that the TATA box and CAAT b ox regions are also important for the rpL34 promoter activity in addit ion to the 50 bp upstream region.