This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yang, M.-K. Articles by Sung, V.-L. Search for Related Content PubMed PubMed Citation Articles by Yang, M.-K. Articles by Sung, V.-L. Agricola Articles by Yang, M.-K. Articles by Sung, V.-L.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, July 2005, p. 3589-3598, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3589-3598.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Identification and Characterization of a Second lexA Gene of Xanthomonas axonopodis Pathovar citri

Mei-Kwei Yang,^* Shu-Ray Su, and Vin-Long Sung

Department of Life Science, Fu Jen University, Taipei, Taiwan, Republic of China

Received 1 October 2004/ Accepted 20 January 2005

We previously identified and characterized a lexA gene from Xanthomonas axonopodis pv. citri. For this study, we cloned and expressed a lexA homologue from X. axonopodis pv. citri. This gene was designated lexA2, and the previously identified lexA gene was renamed lexA1. The coding region of lexA2 is 606 bp long and shares 59% nucleotide sequence identity with lexA1. Analyses of the deduced amino acid sequence revealed that LexA2 has structures that are characteristic of LexA proteins, including a helix-turn-helix DNA binding domain and conserved amino acid residues required for the autocleavage of LexA. The lexA2 mutant, which was constructed by gene replacement, was 4 orders of magnitude more resistant to the DNA-damaging agent mitomycin C at 0.1 µg/ml and 1 order of magnitude more resistant to another DNA-damaging agent, methylmethane sulfonate at 30 µg/ml, than the wild type. A lexA1 lexA2 double mutant had the same degree of susceptibility to mitomycin C as the lexA1 or lexA2 single mutant but was 1 order of magnitude more resistant to methylmethane sulfonate at 30 µg/ml than the lexA1 or lexA2 single mutant. These results suggest that LexA1 and LexA2 play different roles in regulating the production of methyltransferases that are required for repairing DNA damage caused by methylmethane sulfonate. A mitomycin C treatment also caused LexA2 to undergo autocleavage, as seen with LexA1. The results of electrophoresis mobility shift assays revealed that LexA2 does not bind the lexA1 promoter. It binds to both the lexA2 and recA promoters. However, neither LexA2 nor LexA1 appears to regulate recA expression, as lexA1, lexA2, and lexA1 lexA2 mutants did not become constitutive for recA transcription and RecA production. These results suggest that recA expression in X. axonopodis pv. citri is regulated by mechanisms that have yet to be identified.

---

* Corresponding author. Mailing address: Department of Life Science, Fu Jen University, 510 Chun-Chen Road, Taipei 242, Taiwan, Republic of China. Phone: 886 2 29052462. Fax: 886 2 29059123. E-mail: mkyang{at}mails.fju.edu.tw.

---

Applied and Environmental Microbiology, July 2005, p. 3589-3598, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3589-3598.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Lee, J.-H., Geiman, D. E., Bishai, W. R. (2008). Role of Stress Response Sigma Factor SigG in Mycobacterium tuberculosis. J. Bacteriol. 190: 1128-1133 [Abstract] [Full Text]  
• Hare, J. M., Perkins, S. N., Gregg-Jolly, L. A. (2006). A Constitutively Expressed, Truncated umuDC Operon Regulates the recA-Dependent DNA Damage Induction of a Gene in Acinetobacter baylyi Strain ADP1.. Appl. Environ. Microbiol. 72: 4036-4043 [Abstract] [Full Text]