BINDING-SPECIFICITY AND TISSUE-SPECIFIC EXPRESSION PATTERN OF THE ARABIDOPSIS BZIP TRANSCRIPTION FACTOR TGA2

The binding specificity and tissue-specific expression pattern of TGA2 (AHBP-1b), an Arabidopsis bZIP transcription factor have been determi ned. Filter-binding and gel-shift assays showed that TGA2 has high aff inity for C-boxes (ATGACGTCAT). In this respect TGA2 is similar to oth er members of the Arabidopsis TGA family (such as TGA1, TGA3 and OBF4) and to tobacco TGA1a. Genomic Southern blot analysis confirmed that T GA2 is a member of a gene family. Northern blot analysis showed that t he gene is expressed at similar levels in root, stem, leaf and flower and at somewhat lower levels in siliques. TGA3 was also found to be ex pressed at the same level throughout the plant, whereas genes encoding TGA1 and OBF4 have relatively high RNA expression levels in root. The differential expression of these genes suggests that they have distin ct functions.