A multiple-stimuli-responsive as-1-related element of parA gene confers responsiveness to cadmium but not to copper.
The expression of parA, an auxin-regulated gene expressed during the culture of tobacco (Nicotiana tabacum L.) mesophyll protoplasts, is induced by cadmium. To identify the cadmium-responsive element, we examined the parA promoter using the GUS reporter gene. Cadmium responsiveness was retained in a 5' deletion of the parA promoter to -78 bp, but it was nullified by further deletion to -49bp, which implies that the region -49 to -78 bp contained a cadmium-responsive element. This region contains a sequence similar to as-1, an enhancer sequence from the cauliflower mosaic virus 35S RNA promoter that binds the nuclear factor ASF-1. We named the sequence in the parA promoter pas. Gel-shift assays revealed that pas and as-1 compete for the same DNA-binding nuclear protein(s). Since pentamers of either pas and as-1 were able to confer cadmium responsiveness on a minimal promoter but mutant as-1 was not, we propose that pas and as-1 are involved in cadmium-responsive gene expression. Neither pas nor as-1 conferred responsiveness to copper. The specificity of this response, involving the function of as-1-related elements including pas, is discussed.
Kusaba
M
M
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan. kusaba@irb.affrc.go.jp
Takahashi
Y
Y
Nagata
T
T
D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology*; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology*; D018744:DNA, Plant; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000166:cytology / Q000235:genetics
D018744:DNA, Plant; D010940:Plant Proteins; D002104:Cadmium; D003300:Copper; D005966:Glucuronidase