A GCC element and a G-box motif participate in ethylene-induced expression of the PRB-1b gene.
The PRB-1b gene codes for a basic-type pathogenesis-related protein and is activated at the transcriptional level by the plant hormone ethylene. To identify cis-acting DNA elements essential for ethylene induction, deleted and mutant forms of the PRB-1b promoter, fused to the beta-glucuronidase (GUS) coding region, were introduced in transgenic tobacco plants. A 73 bp fragment (X1 region) of the PRB-1b promoter, located between positions -213 and -141, was sufficient to confer ethylene responsiveness to the reporter gene. The X1 region contains a TAAGAGCCGCC motif (GCC-box) well conserved in several ethylene-inducible genes. A substitution mutation in this sequence, in the context of a 213 bp PRB-1b promoter, completely abolished ethylene induction in transgenic tobacco, defining this conserved motif as part of a cis-acting element responsive to ethylene. Three other mutations in the X1 region caused a pronounced decrease in the PRB-1b promoter activity in transgenic plants, but did not affect ethylene inducibility. One of them, localized in a G-box like motif (CACGTG), disrupted the binding site for a nuclear factor, as observed in gel-shift analysis. Interestingly, the mobility of the complex formed on the G-box element was dependent on its phosphorylation state. These results suggest that a cis-acting element involved in the perception of the ethylene signal resides in a GCC motif and acts in concert with additional elements in the regulation of ethylene-induced PRB-1b expression.
Sessa
G
G
Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel.
Meller
Y
Y
Fluhr
R
R
D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005030:Ethylenes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D009841:Oligonucleotides / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D014026:Nicotiana / Q000235:genetics
D004268:DNA-Binding Proteins; D005030:Ethylenes; D009687:Nuclear Proteins; D009841:Oligonucleotides; D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; C036216:ethylene