State Key Laboratory of Microbial Metabolism and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
PLoS One. 2012;7(6):e39538. doi: 10.1371/journal.pone.0039538. Epub 2012 Jun 25.
Pseudomonas aeruginosa M18, a rhizosphere-isolated bacterial strain showing strong antifungal activity, can produce secondary metabolites such as phenazine-1-carboxylic acid and pyoluteorin (Plt). The LysR-type transcriptional regulator PltR activates the Plt biosynthesis operon pltLABCDEFG, the expression of which is induced by Plt. Here, we identified and characterized the non-conserved pltL promoter (pltLp) specifically activated by PltR and its upstream neighboring lys box from the complicated pltR-pltL intergenic sequence. The 22 bp palindromic lys box, which consists of two 9 bp complementary inverted repeats interrupted by 4 bp, was found to contain the conserved, GC-rich LysR-binding motif (T-N(11)-A). Evidence obtained in vivo from mutational and lacZ report analyses and in vitro from electrophoretic mobility shift assays reveals that the PltR protein directly bound to the pltLp region as the indispensable binding motif "lys box", thereby transcriptionally activating the pltLp-driven plt operon expression. Plt, as a potential non-essential coinducer of PltR, specifically induced the pltLp expression and thus strengthened its biosynthetic plt operon expression.
铜绿假单胞菌 M18 是一种具有强烈抗真菌活性的根际分离细菌株，能够产生吩嗪-1-羧酸和吡咯并[2,1-f][1,2,4]三嗪-1,4-二酮（Plt）等次生代谢物。LysR 型转录调节因子 PltR 激活 Plt 生物合成操纵子 pltLABCDEFG 的表达，该表达受 Plt 诱导。在这里，我们从复杂的 pltR-pltL 基因间序列中鉴定和表征了由 PltR 特异性激活的非保守 pltL 启动子（pltLp）及其上游邻近的 lys 盒。由两个 9 bp 互补反向重复序列组成的 22 bp 回文 lys 盒，被发现含有保守的富含 GC 的 LysR 结合基序（T-N(11)-A）。体内突变和 lacZ 报告分析以及体外电泳迁移率变动分析的证据表明，PltR 蛋白直接与 pltLp 区域结合作为必需的结合基序“lys 盒”，从而转录激活 pltLp 驱动的 plt 操纵子表达。Plt 作为 PltR 的潜在非必需共诱导物，特异性诱导 pltLp 的表达，从而增强其生物合成 plt 操纵子的表达。
