title: Role of the GacS Sensor Kinase in the Regulation of Volatile Production by Plant Growth-PromotingPseudomonas fluorescensSBW25.
abstract: In plant-associatedPseudomonasspecies, the production of several secondary metabolites and exoenzymes is regulated by the GacS/GacA two-component regulatory system (the Gac-system). Here, we investigated if a mutation in the GacS sensor kinase affects the production of volatile organic compounds (VOCs) inP. fluorescensSBW25 (Pf.SBW25) and how this impacts on VOCs-mediated growth promotion and induced systemic resistance ofArabidopsisand tobacco. A total of 205 VOCs were detected by Gas Chromatography Mass Spectrometry forPf.SBW25 and thegacS-mutant grown on two different media for 3 and 6 days. Discriminant function analysis followed by hierarchical clustering revealed 24 VOCs that were significantly different in their abundance betweenPf.SBW25 and thegacS-mutant, which included three acyclic alkenes (3-nonene, 4-undecyne, 1-undecene). These alkenes were significantly reduced by thegacSmutation independently of the growth media and of the incubation time. ForArabidopsis, bothPf.SBW25 and thegacS-mutant enhanced, via VOCs, root and shoot biomass, induced systemic resistance against leaf infections byP. syringaeand rhizosphere acidification to the same extent. For tobacco, however, VOCs-mediated effects on shoot and root growth were significantly different betweenPf.SBW25 and thegacS-mutant. WhilePf.SBW25 inhibited tobacco root growth, thegacS-mutant enhanced root biomass and lateral root formation relative to the non-treated control plants. Collectively these results indicate that the sensor kinase GacS is involved in the regulation of VOCs production inPf.SBW25, affecting plant growth in a plant species-dependent manner.
authors.affiliation: Laboratory of Phytopathology, Wageningen University Wageningen, Netherlands.
authors.forename: Xu
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology Wageningen, Netherlands.
authors.forename: Viviane
authors.initials: V
authors.lastname: Cordovez
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology Wageningen, Netherlands.
authors.forename: Desalegn W
authors.initials: DW
authors.lastname: Etalo
authors.affiliation: Laboratory of Phytopathology, Wageningen University Wageningen, Netherlands.
authors.forename: Menno
authors.initials: M
authors.lastname: van der Voort
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of EcologyWageningen, Netherlands; Institute of Biology Leiden, Leiden UniversityLeiden, Netherlands.
authors.forename: Jos M
authors.initials: JM
authors.lastname: Raaijmakers
keywords: GC-MS; ISR; Pseudomonas; plant growth promotion; two-component regulation; volatile organic compounds