Rhizobacterial volatile organic compounds modulate
biomass production and root architecture in Arabidopsis
thaliana (L.) Heynh. and Brachypodium distachyon (L.) P.
Beauv.
Delaplace Pierre1*, Varin Sébastien1, Ormeño-Lafuente Elena2, Spaepen
Stijn3, Saunier de Cazenave Magdalena1, Blondiaux-Hendrick Adeline1,
Wathelet Jean-Paul4, du Jardin Patrick1
1
University of Liège, Gembloux Agro-Bio Tech, Plant Biology Unit,
Gembloux, Belgium
2
Current address : Centre National de la Recherche Scientifique, Institut
Ecologie et Environnement, Institut Méditerranéen d'Ecologie et
Paléoécologie, UMR CNRS 6116, Laboratoire de Diversité Fonctionnelle
des Communautés Végétales, Marseille, France
3
Centre of Microbial and Plant Genetics, K.U.Leuven, Bio-incubator,
Heverlee, Belgium
4
University of Liège, Gembloux Agro-Bio Tech, General and Organic
Chemistry Unit, Gembloux, Belgium
* Pierre.delaplace@ulg.ac.be
The ability of plants to take up water and mineral nutrients from the soil
depends on their capacity to develop an extensive root system and on
the interactions of roots with their soil environment, the rhizosphere.
Studies of the mechanisms involved in the communication between plant
growth-promoting soil micro-organisms and the root system is expected
to lead to improved fertility management strategies. Up to now, the
characterization of such interactions has been mainly focused on liquid
diffusates but it has been recently reported that volatile organic
compounds (VOC) also play a role as chemical messengers in positive
interactions occurring in the rhizosphere and involving plants, bacteria,
fungi and insects [1-2].
In this context, this project aims to better understand the ecophysiology
of the rhizosphere of Arabidopsis thaliana and Brachypodium distachyon.
For this purpose, a collection of 18 rhizobacterial strains belonging to
nine genera were selected for their potential growth promotion ability.
The VOC-emission capacity of each strain was measured after 24 and
48 hours of growth on agar media [3] using solid-phase microextraction
followed by gas chromatography coupled to a mass spectrometer.
In parallel, an in vitro screening system was set up to assess VOCmediated plant-growth promotion ability of the selected strains. This
system separates physically the plant and the bacteria while allowing
interactions through VOC for 10 days within a shared atmosphere. For
Arabidopsis, two inoculum sizes were considered: 2*105 and 2*106 cfu,
using biological triplicates. At the end of the process, leaf and root
biomasses, leaf area, primary root length, lateral root number and lateral
root length were measured to assess the effects of bacterial VOC on
plant growth. Experiments are in progress to characterize such
parameters on Brachypodium in order to compare the response of both
model species to rhizobacterial volatile perception.
1. Ryu CM, Farag MA, Hu CH, Reddy MS, Wei HX, Paré PW, Kloepper JW (2003)
Bacterial volatiles promote growth in Arabidopsis. Proc Natl Acad Sci USA 8: 49274932.
2. Kai M, Effmert U, Berg G, Piechulla B (2007) Volatiles of bacterial antagonists
inhibit mycelial growth of the plant pathogen Rhizoctonia solani. Arch Microbiol 187:
351-360.
3. Farag MA, Ryu CM, Sumner LW, Paré PW (2006) GC–MS SPME profiling of
rhizobacterial volatiles reveals prospective inducers of growth promotion and induced
systemic resistance in plants. Phytochemistry 67: 2262-2268.
Keywords: root architecture, plant growth-promoting rhizobacteria,
volatile organic compounds, rhizosphere
Acknowledgements: this work was supported by the Belgian Fonds de la
Recherche Scientifique (FRFC project 2.4.591.10. and postdoctoral grant
1808458).