Proton-transfer-reaction mass spectrometry as a new tool for real time analysis of root-secreted volatile organic compounds in Arabidopsis

• Published in: Plant physiology (Bethesda) 2004-05, Vol.135 (1), p.47-58
• Main Authors: Steeghs, M, Bais, H.P, De Gouw, J, Goldan, P, Kuster, W, Northway, M, Fall, R, Vivanco, J.M
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alternaria brassicicola; Animals; Aphidoidea; Arabidopsis - metabolism; Arabidopsis - microbiology; Arabidopsis - parasitology; Arabidopsis thaliana; Average linear density; Bacteria - growth & development; Biological and medical sciences; Breakthrough Technologies; Computer Systems; Cyclohexanols - metabolism; Diuraphis noxia; Economic plant physiology; emissions; Ethanol; Eucalyptol; Fundamental and applied biological sciences. Psychology; Fungi - growth & development; gas chromatography; Gas Chromatography-Mass Spectrometry; Genes. Genome; Immunity, Innate; Infections; insect pests; Insecta - growth & development; Ions; kinetics; mass spectrometry; Mass Spectrometry - instrumentation; Mass Spectrometry - methods; Mass spectroscopy; mechanical damage; Molecular and cellular biology; Molecular genetics; Monoterpenes - metabolism; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Organic Chemicals - metabolism; Pathogens; plant damage; Plant Diseases - microbiology; Plant Diseases - parasitology; Plant interaction; plant pathogenic bacteria; plant pathogenic fungi; plant pests; plant response; Plant roots; Plant Roots - metabolism; Plant Roots - microbiology; Plant Roots - parasitology; Plants; proton-transfer-reaction mass spectrometry; Protons; Pseudomonas syringae; rhizosphere; root exudates; roots; Stress, Mechanical; Volatile organic compounds; Volatilization
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.038703

Plant roots release about 5% to 20% of all photosynthetically-fixed carbon, and as a result create a carbon-rich environment for numerous rhizosphere organisms, including plant pathogens and symbiotic microbes. Although some characterization of root exudates has been achieved, especially of secondary metabolites and proteins, much less is known about volatile organic compounds (VOCs) released by roots. In this communication, we describe a novel approach to exploring these rhizosphere VOCs and their induction by biotic stresses. The VOC formation of Arabidopsis roots was analyzed using proton-transfer-reaction mass spectrometry (PTR-MS), a new technology that allows rapid and real time analysis of most biogenic VOCs without preconcentration or chromatography. Our studies revealed that the major VOCs released and identified by both PTR-MS and gas chromatography-mass spectrometry were either simple metabolites, ethanol, acetaldehyde, acetic acid, ethyl acetate, 2-butanone, 2,3,-butanedione, and acetone, or the monoterpene, 1,8-cineole. Some VOCs were found to be produced constitutively regardless of the treatment; other VOCs were induced specifically as a result of different compatible and noncompatible interactions between microbes and insects and Arabidopsis roots. Compatible interactions of Pseudomonas syringae DC3000 and Diuraphis noxia with Arabidopsis roots resulted in the rapid release of 1,8-cineole, a monoterpene that has not been previously reported in Arabidopsis. Mechanical injuries to Arabidopsis roots did not produce 1,8-cineole nor any C6 wound-VOCs; compatible interactions between Arabidopsis roots and Diuraphis noxia did not produce any wound compounds. This suggests that Arabidopsis roots respond to wounding differently from above-ground plant organs. Trials with incompatible interactions did not reveal a set of compounds that was significantly different compared to the noninfected roots. The PTR-MS method may open the way for functional root VOC analysis that will complement genomic investigations in Arabidopsis.