title: The RNA chaperone Hfq regulates antibiotic biosynthesis in the rhizobacterium Pseudomonas aeruginosa M18.
abstract: The rhizosphere microbe Pseudomonas aeruginosa M18 shows strong antifungal activities, mainly due to the biosynthesis of antibiotics like pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA). The ubiquitous RNA chaperone Hfq regulates bacterial virulence and stress tolerance through global posttranscriptional regulation. Here, we explored the molecular mechanism by which Hfq controls antibiotic biosynthesis in P. aeruginosa M18. The robust downregulation of Plt biosynthesis by Hfq was mediated exclusively by the posttranscriptional downregulation of the plt transcriptional activator PltR. Hfq posttranscriptionally repressed phzM expression and consequently reduced the conversion of PCA to pyocyanin. However, Hfq positively controlled the phz2 operon and PCA biosynthesis through both QscR-mediated transcriptional regulation at the promoter and an unknown regulation at the operator. Also, Hfq was shown to directly bind at the mRNA 5' untranslated leaders of pltR, qscR, and phzM. These three negatively regulated target genes of Hfq shared a similar secondary structure with a short single-stranded AU-rich spacer (a potential Hfq-binding motif) linking two stem-loops. Taken together, these results indicate that Hfq, potentially in collaboration with unknown small noncoding RNAs (sRNAs), tightly controls antibiotic biosynthesis through both direct posttranscriptional inhibition and indirect transcriptional regulation.
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Guohao
authors.initials: G
authors.lastname: Wang
authors.forename: Xianqing
authors.initials: X
authors.lastname: Huang
authors.forename: Sainan
authors.initials: S
authors.lastname: Li
authors.forename: Jiaofang
authors.initials: J
authors.lastname: Huang
authors.forename: Xue
authors.initials: X
authors.lastname: Wei
authors.forename: Yaqian
authors.initials: Y
authors.lastname: Li
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001483:Base Sequence; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D035001:Host Factor 1 Protein / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D000900:Anti-Bacterial Agents; D035001:Host Factor 1 Protein; D018832:Molecular Chaperones; D012329:RNA, Bacterial