ppGpp controlled by the Gac/Rsm regulatory pathway sustains biocontrol activity in Pseudomonas fluorescens CHA0.
ppGpp controlled by the Gac/Rsm regulatory pathway sustains biocontrol activity in Pseudomonas fluorescens CHA0.
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DOI：
10.1094/mpmi-02-12-0034-r
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
K. Takeuchi;Kosumi Yamada;D. Haas
中科院分区：
文献类型：
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作者：
K. Takeuchi;Kosumi Yamada;D. Haas
在荧光假单胞菌 CHA0 和其他荧光假单胞菌中，Gac/Rsm 信号转导途径通过表达调节性小 RNA (sRNA) 有助于根部病原体的次生代谢和生物防治。此外，在菌株 CHA0 中，克雷布斯循环的不平衡会影响菌株产生细胞外次级代谢产物（包括生物防治因子）的能力。在这里，我们报告了野生型 CHA0 的代谢组，这是一种 gacA 阴性突变体，它失去了 Gac/Rsm 活性，而 retS 阴性突变体则表现出强烈增强的 Gac/Rsm 依赖性活性。基于毛细管电泳的代谢组学分析显示，gacA 和 retS 突变对许多中心代谢物的细胞内水平具有相反的影响，表明 Gac/Rsm 途径不仅调节菌株 CHA0 的次级代谢，还调节初级代谢。在鉴定的调节代谢物中，警报酮四磷酸鸟苷 (ppGpp) 通过构建 relA（针对 ppGpp 合酶）和 spoT（针对 ppGpp 合酶/水解酶）缺失突变体进行了详细表征。在relA spoT双突变体中，ppGpp合成完全被废除，Rsm sRNA的表达减弱，抗生素产生、根部定殖和植物保护等生理功能显着减弱。因此，ppGpp 似乎对于维持菌株 CHA0 的附生适应性和生物防治活性至关重要。
In Pseudomonas fluorescens CHA0 and other fluorescent pseudomonads, the Gac/Rsm signal transduction pathway is instrumental for secondary metabolism and biocontrol of root pathogens via the expression of regulatory small RNAs (sRNAs). Furthermore, in strain CHA0, an imbalance in the Krebs cycle can affect the strain's ability to produce extracellular secondary metabolites, including biocontrol factors. Here, we report the metabolome of wild-type CHA0, a gacA-negative mutant, which has lost Gac/Rsm activities, and a retS-negative mutant, which shows strongly enhanced Gac/Rsm-dependent activities. Capillary electrophoresis-based metabolomic profiling revealed that the gacA and retS mutations had opposite effects on the intracellular levels of a number of central metabolites, suggesting that the Gac/Rsm pathway regulates not only secondary metabolism but also primary metabolism in strain CHA0. Among the regulated metabolites identified, the alarmone guanosine tetraphosphate (ppGpp) was characterized in detail by the construction of relA (for ppGpp synthase) and spoT (for ppGpp synthase/hydrolase) deletion mutants. In a relA spoT double mutant, ppGpp synthesis was completely abolished, the expression of Rsm sRNAs was attenuated, and physiological functions such as antibiotic production, root colonization, and plant protection were markedly diminished. Thus, ppGpp appears to be essential for sustaining epiphytic fitness and biocontrol activity of strain CHA0.