AUTHOR=Cheng Xu , Cordovez Viviane , Etalo Desalegn W. , van der Voort Menno , Raaijmakers Jos M. 

TITLE=Role of the GacS Sensor Kinase in the Regulation of Volatile Production by Plant Growth-Promoting Pseudomonas fluorescens SBW25

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01706

DOI=10.3389/fpls.2016.01706

ISSN=1664-462X

ABSTRACT=<p>In plant-associated <italic>Pseudomonas</italic> species, 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) in <italic>P. fluorescens</italic> SBW25 (<italic>Pf</italic>.SBW25) and how this impacts on VOCs-mediated growth promotion and induced systemic resistance of <italic>Arabidopsis</italic> and tobacco. A total of 205 VOCs were detected by Gas Chromatography Mass Spectrometry for <italic>Pf.</italic> SBW25 and the <italic>gacS</italic>-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 between <italic>Pf.</italic>SBW25 and the <italic>gacS</italic>-mutant, which included three acyclic alkenes (3-nonene, 4-undecyne, 1-undecene). These alkenes were significantly reduced by the <italic>gacS</italic> mutation independently of the growth media and of the incubation time. For <italic>Arabidopsis</italic>, both <italic>Pf.</italic>SBW25 and the <italic>gacS</italic>-mutant enhanced, via VOCs, root and shoot biomass, induced systemic resistance against leaf infections by <italic>P. syringae</italic> and rhizosphere acidification to the same extent. For tobacco, however, VOCs-mediated effects on shoot and root growth were significantly different between <italic>Pf.</italic>SBW25 and the <italic>gacS</italic>-mutant. While <italic>Pf.</italic>SBW25 inhibited tobacco root growth, the <italic>gacS</italic>-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 in <italic>Pf.</italic>SBW25, affecting plant growth in a plant species-dependent manner.</p>