7-hydroxytropolone is the main metabolite responsible for the fungal antagonism of Pseudomonas donghuensis strain SVBP6
7-hydroxytropolone is the main metabolite responsible for the fungal antagonism of Pseudomonas donghuensis strain SVBP6
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DOI：
10.1111/1462-2920.14925
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发表时间：
2020-02-05
影响因子：
5.1
通讯作者：
Valverde, Claudio
中科院分区：
文献类型：
--
作者：
Muzio, Federico M.;Agaras, Betina C.;Valverde, Claudio
东湖假单胞菌SVBP 6是从阿根廷农田中分离的一种菌株，具有广谱和可扩散的抗真菌活性，该活性需要功能性gacS基因，但尚不能归因于假单胞菌生防物种典型的次生代谢产物。在这里，我们报告说，Tn 5诱变允许鉴定的基因簇参与真菌的拮抗作用和生产的可溶性tropolectin化合物。乙酸乙酯提取物对菜豆茎枯病菌的抑制作用呈剂量依赖性。通过光谱和X-射线分析，将有机提取物中存在的主要化合物鉴定为7-羟基托酚酮（7 HT）。通过制备2个关键衍生物2，3-二甲氧基和2，7-二甲氧基托品酮，证实了其结构和互变异构性。7 HT（而不是2，3-或2，7-二甲氧基-托品酮）模拟了培养物上清液乙酸乙酯提取物的真菌抑制活性。7 HT的活性，以及它的生产，几乎没有受到影响的存在下，高达50 μ M的添加铁（Fe+2）。综上所述，东湖假单胞菌SVBP 6在Gac-Rsm级联的正调控下产生7 HT，并且是负责广谱抑制不同植物病原真菌的主要活性代谢物。
Pseudomonas donghuensis strain SVBP6, an isolate from an agricultural plot in Argentina, displays a broad-spectrum and diffusible antifungal activity, which requires a functional gacS gene but could not be ascribed yet to known secondary metabolites typical of Pseudomonas biocontrol species. Here, we report that Tn5 mutagenesis allowed the identification of a gene cluster involved in both the fungal antagonism and the production of a soluble tropolonoid compound. The ethyl acetate extract from culture supernatant showed a dose-dependent inhibitory effect against the phytopathogenic fungus Macrophomina phaseolina. The main compound present in the organic extract was identified by spectroscopic and X-ray analyses as 7-hydroxytropolone (7HT). Its structure and tautomerism was confirmed by preparing the two key derivatives 2,3-dimethoxy- and 2,7-dimethoxy-tropone. 7HT, but not 2,3- or 2,7-dimethoxy-tropone, mimicked the fungal inhibitory activity of the ethyl acetate extract from culture supernatant. The activity of 7HT, as well as its production, was barely affected by the presence of up to 50 mu M added iron (Fe+2). To summarize, P. donghuensis SVBP6 produces 7HT under the positive control of the Gac-Rsm cascade and is the main active metabolite responsible for the broad-spectrum inhibition of different phytopathogenic fungi.