THE PLANT CELL, Vol 4, Issue 12 1485-1493, Copyright © 1992 by American Society of Plant Biologists
Two G-Box-Related Sequences Confer Different Expression Patterns in Transgenic Tobacco
J. Salinas, K. Oeda and N. H. Chua
Laboratory of Plant Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, New York 10021-6399
We have analyzed the expression patterns conferred by two G-box-related
motifs, a perfect palindromic sequence (PA, 5[prime]-GCCACGTGGC-3[prime])
and motif I (Iwt, 5[prime]-GTACGTGGCG-3[prime]), in transgenic tobacco
plants. A mutant version of motif I, Imu, was used as a negative control.
PA is present in the promoters of several different genes, whereas Iwt is a
conserved sequence found in abscisic acid-inducible promoters. Previously
we have demonstrated that PA and Iwt, but not Imu, can bind to the tobacco
transcription activator TAF-1 in vitro, with the PA sequence showing a
70-fold higher affinity as compared to Iwt. We found that tetramers of PA
and Iwt, which differ by only 2 bp per 10-bp repeat, confer very different
tissue-specific and expression patterns in transgenic tobacco plants. PA
confers preferential expression in root tissues with a low level of
activity in leaves, whereas Iwt directs developmentally regulated
expression in seeds beginning 15 days after petals have fully expanded
until seed maturation. Imu appears to be inactive because it gives the same
expression pattern as the -90 cauliflower mosaic virus 35S promoter
control. RNA gel blot analysis showed that the expression pattern of TAF-1
mRNA is similar to that directed by PA, suggesting that TAF-1 may be
involved in the transcriptional regulation of PA.
