| Degradation of ROS (reactive oxygen species) is an effective approach of bacteria to protect against oxidation and infest plant.. One side as a defense response in the host cell high level of ROS will be produced rapidly to kill the intruded microorganism when the host was infested by bacteria, and on the other side, respiratory metabolism of cells under aerobic conditions lead to the generation of H2O2,O2- and OH-.The ROS made the cell under a high oxidative stress. ROS could induce damage happen and many cellular components (proteins, lipid and nucleic acid)will be destroyed by ROS when it accumulates to a high level in the cell. If the ROS can't be degraded timely, it will threaten to life. The bacteria should be survival if it wants to infest the host. many high-performance detoxificational systems which consist of many enzymes and proteins including peroxidase, catalase and SOD will be formed in vivo bacteria to survive and colonizein vivo host, also for degrading toxitic sustances produced by respiring itself.. In the system the key members are some regulate proteins such as OxyR, PerR, OhrR, SoxR and so on. These rugulators and enzymes formed regluons function on detoxification of ROS to protect the bacteria against the attack. The OxyR regulon,which belongs to the LysR family of transcription activators, is the protein to recognizing and regulating H2O2,it consists of genes katG, ahpC, ahpF, dps coding peroxidase and gor, grxA,trxC involved in keeping redox balance.Bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most important bacterial diseases in many parts of the world. The disease system becomes one of the most important model system to study the plant-pathogen interactions. However, up to now, regulating mechanism of transcription regulator OxyRxoo to H2O2 degradation was not clear. It has been show that OxyRxooinvoled in many physiological metabolisms of bacteria including antioxidant, spontaneous mutation, pathogenicity, iron metabolism and change of outer membrane protein of bacteria. Regulating mechanism of transcription regulator OxyRxoo to H2O2 degradation is the needs of developing new\effective and sustainable methods and strategy of disease control.To elucidate the role of OxyRxoo, a homologue of OxyR from Xanthomonas oryzae pv. oryzae (Xoo) in detoxification of hydrogen peroxide, previous studies has initially identified that construction domain HTH was the conservative domain combining with DNA, and stimulate the gene transcription by combining. promoter region of target genes in downstream to regulate detoxication of pathogenic bacteria to H2O2OxyRxoo gene fragment was amplified by PCR using specific primers from the genomic DNA of the wild-type PXO99A of Xoo. The sequence of the oxyRxoo was the same as KACC10331 in GenBank.â–³oxyRxoo-HTH, the gene deletion mutants were constructed after a double exchange and homologous recombination inner deleted the HTH domain through marker exchange. Complementary strainsâ–³oxyRxoo-HTH-C was constructed by transforming complementary vector pHM-OxyRxoo into mutantâ–³oxyRxoo-HTH.Compared to wild-type strain PXO99A, there was no difference in bacterial growth in vitro culture ofâ–³oxyRxoo-HTH, but resistance to H2O2 significantly decreased, which can be recovered by gene complementation. The results showed that HTH domain play a key role in degrading peroxide.In conclusion, and construction and key role of HTH domain of oxyRxoo gene in detoxification of hydrogen peroxide have been elucidated in this study.It laid the foundation for studying deeply on the mechnism of OxyRxoo regulon... |
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