Genetic and molecular analysis of a regulatory region of the herbicide 2,4-dichlorophenoxyacetate catabolic plasmid pJP4.
In Alcaligenes eutrophus JMP134, pJP4 carries the genes coding for 2,4-dichlorophenoxyacetate (2,4-D) and 3-chlorobenzoate (3-Cba) degradation plus mercury resistance. The plasmid genes specifying 2,4-D and 3-Cba catabolism are organized in three operons: tfdA, tfdB, and tfdCDEF. Regulation of these operons by two unlinked genes, tfdR and tfdS, has been proposed. Physical and DNA sequence analyses revealed that the tfdR and tfdS genes were identical and were located within a longer inverted repeat of 1592 bp. Similar stem-loop structures were observed among other 2,4-D plasmids. The tfdR gene is 888 bp long and capable of encoding a polypeptide of 32 kDa. The deduced amino acid sequence of tfdR indicates that it is a member of the LysR-type activators. Investigation of the regulation of the catabolic gene clusters through the construction of a pJP4 defined deletion mutant, pYG1010, which lacks a 4.2 kilobase Xbal fragment containing the inverted repeat region carrying the tfdR and tfdS regulatory genes, showed that Pseudomonas cepacia strains containing pYG1010 became 2,4-D negative, but 3-Cba positive. In vivo recombinants of pYG1010 and a cloned tfdS gene rescued the 2,4-D phenotype, indicating that TfdS is a positive regulator of tfdA expression, but not for tfdCDEF expression.
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Department of Biology, California State University, Fresno 93740, USA.
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D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D000421:Alcaligenes / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D016956:Burkholderia cepacia / Q000235:genetics / Q000378:metabolism; D002723:Chlorobenzoates / Q000378:metabolism; D002874:Chromosome Mapping; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids / Q000737:chemistry*; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D014157:Transcription Factors
D001426:Bacterial Proteins; D002723:Chlorobenzoates; D004268:DNA-Binding Proteins; C086733:TfdR protein, Alcaligenes eutrophus; D014157:Transcription Factors; C036427:3-chlorobenzoic acid; D015084:2,4-Dichlorophenoxyacetic Acid