چكيده لاتين :
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 H20 2 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 ofABC transporter systems with an ABC subunit and two penneases.
