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Transcription factor RF2a alters expression of the rice tungro bacilliform virus promoter in transgenic tobacco plants
- Petruccelli, S., Dai, S., Carcamo, R., Yin, Y., Chen, S., Beachy, R.N.
- Proceedings of the National Academy of Sciences of the United States of America 2001 v.98 no.13 pp. 7635-7640
- Nicotiana tabacum, Rice tungro bacilliform virus, transgenic plants, transcription factors, recombinant DNA, beta-glucuronidase, gene expression, DNA-binding domains, phloem, promoter regions, binding sites, histochemistry
- The promoter from rice tungro bacilliform badnavirus (RTBV) is expressed only in phloem tissues in transgenic rice plants. RF2a, a b-Zip protein from rice, is known to bind to the Box II cis element near the TATA box of the promoter. Here, we report that the full-length RTBV promoter and a truncated fragment E of the promoter, comprising nucleotides -164 to +45, result in phloem-specific expression of beta-glucuronidase (GUS) reporter genes in transgenic tobacco plants. When a fusion gene comprising the cauliflower mosaic virus 35S promoter and RF2a cDNA was coexpressed with the GUS reporter genes, GUS activity was increased by 2-20-fold. The increase in GUS activity was positively correlated with the amount of RF2a, and the expression pattern of the RTBV promoter was altered from phloem-specific to constitutive. Constitutive expression of RF2a did not induce morphological changes in the transgenic plants. In contrast, constitutive overexpression of the b-ZIP domain of RF2a had a strong effect on the development of transgenic plants. These studies suggest that expression of the b-Zip domain can interfere with the function of homologues of RF2a that regulate development of tobacco plants.