Characterization of stress-responsive genes, hrcA-grpE-dnaK-dnaJ, from phytopathogenic Xanthomonas campestris

Weng, SF Tai, PM Yang, CH Wu, CD Tsai, WJ Lin, JW Tseng, YH

Sf. Weng et al., Characterization of stress-responsive genes, hrcA-grpE-dnaK-dnaJ, from phytopathogenic Xanthomonas campestris, ARCH MICROB, 176(1-2), 2001, pp. 121-128

34

INGLESE

Article

Microbiology

ARCHIVES OF MICROBIOLOGY

0302-8933 → ACNP

176

1-2

2001

121 - 128

ISI

0302-8933(200107)176:1-2<121:COSGHF>2.0.ZU;2-2

Sequencing of a 6.4-kb DNA fragment, cloned from the plant pathogenic bacte rium Xanthomonas campestris pv. campestris 17 revealed five ORFs whose dedu ced amino acid sequences show strong similarities to the bacterial HrcA, Gr pE, DnaK, DnaJ, and PdxK. The four heat shock genes are organized in the or der hrcA-grpE-dnaK-dnaJ, a genome organization found in many gram-positive bacteria, but only in one gram-negative species (Xylella fastidiosa). These observations suggest that the HrcA-CIRCE system, comprising at least four genes arranged in this order, already existed for the regulation of stress responses before bacteria diverged into gram-negative and gram-positive gro ups. Primer-extension results suggested the presence of promoters at the re gions upstream of grpE and dnaK. In the presence of stress, heat or ethanol (4%), the X. campestris pv. campestris 17 grpE and dnaK promoters were ind uced two- to three-fold over controls. Since the grpE and dnaK promoters po ssess E. Coli sigma (32) promoter-like sequences, they are functional in E. coli, although at levels much lower than in X. campestris pv. campestris 1 7. Furthermore, expression of the X. campestris pv. campestris 17 dnaK prom oter in E. coli was elevated by the cloned X. campestris sigma (32) gene, i ndicating that the cognate sigma (32) works more efficiently for the X. cam pestris promoters.