Sequence-specific binding of protein factors to two independent promoter regions of the acidic tobacco pathogenesis-related-1 protein gene (PR-1).

Gel shift mobility analysis, using the proximal 0.3 kb fragment of the tobacco pathogenesis-related protein 1a gene (PR-1a) and nuclear extracts from healthy Samsun NN tobacco leaves, which do not produce PR-1 proteins, showed a broad shifted signal with low mobility. This signal was not detected with nuclear proteins from the interspecific hybrid of Nicotiana glutinosa x Nicotiana debneyi, which constitutively produces the PR-1a protein. Similar shifted signals were detected with both proximal and distal regions of the 0.3 kb fragment using nuclear proteins from healthy Samsun NN tobacco, but not with proteins from the interspecific hybrid. Further experiments, performed using 5' or 3' truncated fragments of the 0.3 kb fragment, identified two independent binding sites: a distal site between -179 and -168 bp from the transcription start site, and a proximal site between -61 and -37 bp. Footprint analysis revealed two protected sequences, a distal region between -184 and -172 bp, and a proximal region between -68 and -51 bp. These results indicate the presence of regulatory factor(s) for expression of the acidic PR-1a gene. The possibility of negative regulation of the gene is discussed.