title: Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway.
abstract: Lysobacter enzymogenesis a ubiquitous soil gammaproteobacterium that produces a broad-spectrum antifungal antibiotic, known as heat-stable antifungal factor (HSAF). To increase HSAF production for use against fungal crop diseases, it is important to understand how HSAF synthesis is regulated. To gain insights into transcriptional regulation of the HSAF synthesis gene cluster, we generated a library with deletion mutations in the genes predicted to encode response regulators of the two-component signaling systems inL. enzymogenesstrain OH11. By quantifying HSAF production levels in the 45 constructed mutants, we identified two strains that produced significantly smaller amounts of HSAF. One of the mutations affected a gene encoding a conserved bacterial response regulator, PilR, which is commonly associated with type IV pilus synthesis. We determined thatL. enzymogenesPilR regulates pilus synthesis and twitching motility via a traditional pathway, by binding to thepilApromoter and upregulatingpilAexpression. Regulation of HSAF production by PilR was found to be independent of pilus formation. We discovered that thepilRmutant contained significantly higher intracellular levels of the second messenger cyclic di-GMP (c-di-GMP) and that this was the inhibitory signal for HSAF production. Therefore, the type IV pilus regulator PilR inL. enzymogenesactivates twitching motility while downregulating antibiotic HSAF production by increasing intracellular c-di-GMP levels. This study identifies a new role of a common pilus regulator in proteobacteria and provides guidance for increasing antifungal antibiotic production inL. enzymogenesIMPORTANCEPilR is a widespread response regulator of the two-component system known for regulating type IV pilus synthesis in proteobacteria. Here we report that, in the soil bacteriumLysobacter enzymogenes, PilR regulates pilus synthesis and twitching motility, as expected. Unexpectedly, PilR was also found to control intracellular levels of the second messenger c-di-GMP, which in turn inhibits production of the antifungal antibiotic HSAF. The coordinated production of type IV pili and antifungal antibiotics has not been observed previously.
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xia
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China.
authors.forename: Zhenhe
authors.initials: Z
authors.lastname: Su
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China.
authors.forename: Gaoge
authors.initials: G
authors.lastname: Xu
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Gomelsky
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China glqian@njau.edu.cn fqliu20011@sina.com.
authors.forename: Guoliang
authors.initials: G
authors.lastname: Qian
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China glqian@njau.edu.cn fqliu20011@sina.com.|Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, People's Republic of China.
authors.forename: Fengquan
authors.initials: F
authors.lastname: Liu
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015723:Gene Library; D053528:Lysobacter / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation; D015398:Signal Transduction; D012988:Soil Microbiology
chemical_list: D000935:Antifungal Agents; D001426:Bacterial Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP
keywords: HSAF; Lysobacter; PilR; antibiotics; type IV pili