Dark induction and subcellular localization of the pathogenesis-related PRB-1b protein.
The PRB-1b gene codes for a basic-type pathogenesis-related protein of the PR-1 family of tobacco. PRB-1b mRNA accumulation is induced in response to biotic and abiotic elicitors, such as TMV, ethylene, salicylic acid, alpha-amino butyric acid and darkness. In order to determine the location of elements that control dark-regulated PRB-1b gene expression, we tested promoter, transcribed regions and 3'-downstream regions of the gene for their ability to respond to dark induction in transgenic tobacco plants. An ethylene-inducible promoter region of 863 bp was not able to confer dark induction to a beta-glucuronidase reporter gene, while a construct containing the transcribed region of the gene and 3'-downstream sequences, driven by the cauliflower mosaic virus 35S promoter, was correctly dark-regulated. The results indicate that dark-induction of the PRB-1b gene can be controlled by 3'-downstream elements at the transcriptional level or by transcribed sequences at the post-transcriptional level. A circadian clock regulation of the PRB-1b gene was excluded, as fluctuations of PRB-1b transcript levels were not observed in plants placed in constant light or darkness. Subcellular localization of the PRB-1b protein was also determined, in tobacco protoplasts preparations and in cell cultures. The PRB-1b polypeptide was predominantly detected in protoplast vacuoles and was not secreted to the media in cell cultures. These results support an intracellular localization for the PRB-1b protein, as reported for other basic-type components of the pathogenesis-related proteins family.
Sessa
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Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel.
Yang
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Raz
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Eyal
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Fluhr
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D002478:Cells, Cultured; D002940:Circadian Rhythm; D003624:Darkness; D005030:Ethylenes / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D010947:Plants, Toxic; D012323:RNA Processing, Post-Transcriptional; D012045:Regulatory Sequences, Nucleic Acid; D013347:Subcellular Fractions / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
D005030:Ethylenes; D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; C036216:ethylene