title: The GacS-regulated sigma factor RpoS governs production of several factors involved in biocontrol activity of the rhizobacterium Pseudomonas chlororaphis O6.
abstract: Pseudomonas chlororaphis O6 possesses many beneficial traits involved in biocontrol of plant diseases. In this paper, we examined the effect of a mutation in rpoS encoding a stress-related alternative sigma factor to better understand the regulation of these traits. Biochemical studies indicated that production of acyl homoserine lactones was altered and phenazine was increased in the P. chlororaphis O6 rpoS mutant. The rpoS mutation reduced hydrogen cyanide levels, but the rpoS mutant still displayed a level of in vitro antifungal activity against Fusarium graminearum and Alternaria alternata. Tomato root colonization by the rpoS mutant was lower than that by the wild type at 5, 7, and 13 days after inoculation. The rpoS mutant was less effective than the wild type in induction of systemic resistance to two foliar pathogens after root inoculation of the tomato plants. Our findings demonstrate that the stationary-phase sigma factor RpoS regulates production of several key factors involved in the biocontrol potential of P. chlororaphis O6, some independently of the global regulator GacS.
authors.affiliation: Institute of Environmentally Friendly Agriculture, Chonnam National University, Gwangju, South Korea.
authors.forename: Sang A
authors.initials: SA
authors.lastname: Oh
authors.forename: Ji Soo
authors.initials: JS
authors.lastname: Kim
authors.forename: Song Hee
authors.initials: SH
authors.lastname: Han
authors.forename: Ju Yeon
authors.initials: JY
authors.lastname: Park
authors.forename: Christian
authors.initials: C
authors.lastname: Dimkpa
authors.forename: Chet
authors.initials: C
authors.lastname: Edlund
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Anderson
authors.forename: Young Cheol
authors.initials: YC
authors.lastname: Kim
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism; D000935:Antifungal Agents / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000254:growth & development; D006856:Hydrogen Cyanide / Q000378:metabolism; D018551:Solanum lycopersicum / Q000382:microbiology; D056265:Microbial Interactions; D009154:Mutation / Q000235:genetics; D010619:Phenazines / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology; D011549:Pseudomonas / Q000235:genetics* / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D054742:Acyl-Butyrolactones; D000935:Antifungal Agents; D001426:Bacterial Proteins; D010619:Phenazines; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; D006856:Hydrogen Cyanide; C074165:lemA protein, bacterial