Phenazine-1-carboxamide production in the biocontrol strain Pseudomonas chlororaphis PCL1391 is regulated by multiple factors secreted into the growth medium
Phenazine-1-carboxamide production in the biocontrol strain Pseudomonas chlororaphis PCL1391 is regulated by multiple factors secreted into the growth medium
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DOI：
10.1094/mpmi.2001.14.8.969
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发表时间：
2001-08-01
影响因子：
3.5
通讯作者：
Bloemberg, GV
中科院分区：
文献类型：
--
作者：
Chin-A-Woeng, TFC;van den Broek, D;Bloemberg, GV
绿蚜假单胞菌PCL1391防治番茄根腐病和尖孢镰刀菌引起的番茄根腐病，吩嗪-L-甲酰胺(Pcn)的产生对防治番茄根腐病起着至关重要的作用。在体外，只有在高种群密度下才能观察到PCN的产生，这表明生产受到群体感应的调节。经结构鉴定，PCL1391产生的主要自身诱导剂分子为N-己酰-L-高丝氨酸内酯(C-6-HSL)。另外两个与N-丁酰基-L-高丝氨酸内酯(C4HSL)和N-辛酰基-L-高丝氨酸内酯(C-8-HSL)混合产生的自身诱导剂，以及两个不产生PCN的PCL1391突变株，分别在phzI和phzR基因上存在缺陷，其核苷酸序列已完全测定。PhzI突变体可以通过添加外源合成的C-6-NSL来补充PCN的产生，但不能通过C-4-HSL、C-8-HSL或任何其他被测试的HSL来补充。对报告菌株phzI、phzR和phz生物合成操纵子的表达分析表明，phzI的表达和PCN的产生受C6-HSL以种群密度依赖的方式调节。将调控基因phzI和phzR的多个拷贝引入到不同的质粒上，导致HSLs的产生增加，PCN生物合成操纵子的表达增加，从而PCN的产生以拷贝依赖的方式增加了6倍。令人惊讶的是，我们的表达研究表明，一个额外的，但尚未确定的因子(S)，既不是PCN，也不是C-4-HSL或C-8-HSL，它参与了phzI的正向调节，并能够在生长中的低细胞密度下诱导PCN的生物合成，从而提高PCN的产量。
Pseudomonas chlororaphis PCL1391 controls tomato foot and root rot caused by Fusarium oxysporum f. sp, radicis-lycopersici, The production of phenazine-l-carboxamide (PCN) is crucial for this biocontrol activity. In vitro production of PCN is observed only at high-population densities, suggesting that production is under the regulation of quorum sensing. The main autoinducer molecule produced by PCL1391 was identified structurally as N-hexanoyl-L-homoserine lactone (C-6-HSL). The two other autoinducers that were produced comigrate with N-butanoyl-L-homoserine lactone (C4HSL) and N-octanoyl-L-homoserine lactone (C-8-HSL), Two PCL1391 mutants lacking production of PCN were defective in the genes phzI and phzR, respectively, the nucleotide sequences of which were determined completely. Production of PCN by the phzI mutant could be complemented by the addition of exogenous synthetic C-6-NSL, but not by C-4-HSL, C-8-HSL, or any other HSL tested. Expression analyses of Tn5luxAB reporter strains of phzI, phzR, and the phz biosynthetic operon dearly showed that phzI expression and PCN production is regulated by C6-HSL in a population density-dependent manner. The introduction of multiple copies of the regulatory genes phzI and phzR on various plasmids resulted in an increase of the production of HSLs, expression of the PCN biosynthetic operon, and consequently, PCN production, up to a sixfold increase in a copy-dependent manner. Surprisingly, our expression studies show that an additional, yet unidentified factor(s), which are neither PCN nor C-4-HSL or C-8-HSL, secreted into the growth medium of the overnight cultures, is involved in the positive regulation of phzI and is able to induce PCN biosynthesis at low cell densities in a growing culture, resulting in an increase of PCN production.