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Journal of Biological Sciences
Year: 2008  |  Volume: 8  |  Issue: 2  |  Page No.: 349 - 355

Disruption of drrA Gene Affects the Xanthomonas axonopodis pv. citri Response to Oxidative Stress

Jeny Rachid Cursino-Santos, Luciana Meneguim, Rui Pereira Leite Jr. and Nilce Maria Martinez-Rossi    

Abstract: The deduced amino acid sequence of drrA gene (XAC3759) from Xanthomonas axonopodis pv. citri (Xac) is similar to a variety of earlier described functionally uncharacterized ABC (ATP-Binding Cassette) transporters. In order to investigate the biological process in which this gene is involved, we constructed a drrA deletion mutant strain and tested its susceptibility to drugs with different mechanisms of action and to oxidative stress and also its capability to infect Citrus sinensis. The results showed that Xac responses to seven drugs (tetracycline, penicillin, ampicillin, chloramphenicol, acriflavine, ethidium bromide and doxorubicin chloridrate) and to host infection are independent upon drrA expression. However, Northern Blot analyses revealed that drrA gene is induced as short response to H2O2 exposure, only at the early phase of bacterial growth. Furthermore, the drrA disruption rendered the mutant more sensitive to oxidative stress than the control strain, suggesting that this transporter plays an important role in modulating oxidative stress susceptibility in Xac. Also, the drrA gene is co-transcripted with two hypothetical ORFs (Open Read Frame) as an operon cluster (named here drrABC) when Xac wild type strain was submitted to oxidative stress. The sequence analysis and topology prediction of the deduced proteins from these two neighboring hypothetical ORFs (XAC3758 and XAC3757) show that they have 6 transmembrane segments which are characteristic of permeases, supporting the structure of ABC transporter systems with an ABC subunit and two permeases.

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