天然氨基酸诱导野油菜黄单胞菌降解DSF-家族群体感应信号活性分析

The activities of natural amino acids to induce Xanthomonas campestris to degrade DSF-family quorum sensing signals

摘要:

【背景】野油菜黄单胞菌(Xanthomonas campestris pv. campestris，Xcc)是十字花科植物黑腐病的致病菌。Xcc中DSF (diffusible signal factor)信号依赖的群体感应系统和RpfB介导的群体感应退出机制均与其致病性密切相关。【目的】分别检测18种氨基酸对DSF-家族群体感应信号分子合成的影响，为研发新型生物防治方法提供思路。【方法】添加不同浓度的氨基酸到ΔrpfC菌株XYS培养体系中，接种后不同时间点取样提取DSF信号分子，利用高效液相色谱法(high performance liquid chromatography，HPLC)分析DSF和BDSF浓度。【结果】18种氨基酸中，甲硫氨酸、色氨酸和胱氨酸能有效降低ΔrpfC菌株培养体系中DSF和BDSF水平，抑制效果与氨基酸浓度密切相关；3种氨基酸对DSF信号分子的抑制作用存在叠加效应；甲硫氨酸、色氨酸或胱氨酸不影响ΔrpfCΔrpfB双突变体菌株中DSF和BDSF水平。【结论】首次发现了甲硫氨酸、色氨酸和胱氨酸通过RpfB诱导Xcc退出群体感应状态。

Abstract:

[Background] Xanthomonas campestris pv. campestris (Xcc) is a causal agent of black rot in cruciferous plants. The diffusible signal factor (DSF)-dependent quorum sensing (QS) system and RpfB-dependent QS exit mechanism are closely associated with Xcc pathogenicity. [Objective] We investigated the effects of 18 amino acids on the biosynthesis of DSF-family QS signals, to provide a clue for developing new strategy to control plant diseases. [Methods] The Xcc mutant strain ΔrpfC was grown in the XYS medium supplemented with 18 amino acids, respectively. The crude DSF extracts after 24 h to 36 h inoculation were then analyzed by high performance liquid chromatography (HPLC). [Results] 1) Among the 18 amino acids tested, methionine, tryptophan and cystine were found to significantly decrease DSF and BDSF levels in the ΔrpfC culture. The inhibitory effect was closely associated with amino acid concentration; 2) Additive inhibitory effects between three amino acids were observed; 3) Addition of methionine, tryptophan or cystine had no significant effect on the levels of DSF and BDSF in the ΔrpfCΔrpfB culture. [Conclusion] Methionine, tryptophan and cystine probably induce Xcc to exit from quorum sensing stage via the RpfB-dependent pathway.