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Localization of OccR‐activated and TraR‐activated promoters that express two ABC‐type permeases and the traR gene of Ti plasmid pTiR10
Author(s) -
Fuqua Clay,
Winans Stephen C.
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1996.tb02640.x
Subject(s) - octopine , ti plasmid , operon , biology , promoter , agrobacterium tumefaciens , plasmid , microbiology and biotechnology , genetics , gene , gene expression , mutant , transformation (genetics)
Summary Conjugation of Agrobacterium tumefaciens wide‐host‐range octopine‐type Ti plasmids is regulated by the LuxR‐type transcriptional activator TraR in conjunction with an acylated homoserine lactone designated AAI. Expression of traR in octopine‐type Ti plasmids is stimulated by OccR in response to octopine, an opine released from crown gall tumours, and is also positively autoregulated by TraR and AAI. Genetic and physical mapping of these promoters indicates that the OccR‐activated promoter lies 14.5 kb upstream of traR , while the TraR‐activated promoter lies 6kb upstream. The upstream portion of the 14.5 kb operon contains seven previously characterized genes that direct the uptake and catabolism of octopine. The TraR‐activated promoter lies just downstream from the octopine catabolic genes, and transcribes six genes in addition to traR , including five genes ( ophABCDE ) that show strong homology to oligopeptide permeases of Salmonella typhimurium and Bacillus subtilis. Several TraR‐regulated promoters overlap with 18bp inverted repeats called tra boxes. In contrast, the traR autoregulatory promoter is not associated with a consensus tra box.