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Luo, ZQ and Farrand, SK (1999) Cloning and characterization of a tetracycline resistance determinant present in Agrobacterium tumefaciens C58. J. Bacteriol. 181:618-26


Agrobacterium tumefaciens C58 and its derivatives give rise to spontaneous mutants resistant to tetracycline at a high frequency. We observed that a mutation affecting a tRNA processing function significantly affected the emergence of such mutants, suggesting that C58 contained a positively acting gene conferring resistance to tetracycline. A cosmid clone conferring resistance to tetracycline in Escherichia coli and Agrobacterium was isolated from a genomic bank of one such mutant. Subcloning, transposon mutagenesis, and DNA sequence analysis revealed that this DNA fragment contained two divergently transcribed genes, tetA and tetR, encoding products that were very similar to proteins of the Tet(A) class of tetracycline resistance systems. In the clone from this mutant, tetR was disrupted by an IS426. The homologous region from wild-type NT1 contained an intact tetR gene and did not confer resistance to tetracycline. Hybridization analysis showed that of 22 members of the genus Agrobacterium surveyed, only strains C58 and T37 contained the tet determinant. Moreover, only these two strains mutated to resistance to this antibiotic. Unlike other Tet(A) systems, neither tetracycline nor a series of its derivatives induced the expression of this tet gene unit. Other polycyclic compounds, including many of plant origin, also did not induce this tet gene system. The divergent promoter region of this tet system contained a single inverted repeat element identical to one such operator repeat in the promoter region of the tet determinant from the IncP1alpha R plasmid RP4. TetR repressor proteins from the Agrobacterium tet system and from RP4 interacted with the heterologous operators. While the repressive effect of the TetR protein from strain C58 (TetRC58) on the tetA gene from strain RP4 (tetARP4) was not relieved by tetracycline, repression of tetAC58 by TetRRP4 was lifted by this antibiotic.


PubMed PMC93418


Agrobacterium tumefaciens/drug effects; Agrobacterium tumefaciens/genetics; Agrobacterium tumefaciens/growth & development; Amino Acid Sequence; Antiporters/chemistry; Antiporters/genetics; Antiporters/metabolism; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Base Sequence; Cloning, Molecular; Escherichia coli/genetics; Introns; Molecular Sequence Data; Mutagenesis, Insertional; Regulatory Sequences, Nucleic Acid; Restriction Mapping; Sequence Alignment; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Tetracycline/pharmacology; Tetracycline Resistance/genetics; Trans-Activators; Transcription, Genetic



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:1901326: response to tetracycline



Antibiotics should activate tetA however when tetracycline is introduced to Agrobacterium C58 the tetA gene mutates in a way that causes it to be resistant to activation by tetracycline.



GO:0010467: gene expression



TetRC58 controls whether or not tetR and/or tetA can be expressed. This is supported in Table 2. Expression of tetA allows for the expression of lacZ and when the inducer,arabinose, was added then tetA was repressed by tetR.


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