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GacS-Dependent Production of 2R, 3R-Butanediol by Pseudomonas chlororaphis O6 Is a Major Determinant for Eliciting Systemic Resistance Against Erwinia carotovora but not Against Pseudomonas syringae pv. tabaci in Tobacco

August 2006 , Volume 19 , Number  8
Pages  924 - 930

Song Hee Han , 1 Seung Je Lee , 2 Jae Hak Moon , 2 Keun Hyung Park , 2 Kwang Yeol Yang , 1 Baik Ho Cho , 1 Kil Yong Kim , 1 Yong Whan Kim , 3 Myung Chul Lee , 3 Anne J. Anderson , 4 and Young Cheol Kim 1

1Agricultural Plant Stress Research Center and Environmental-Friendly Agriculture Research Center, and 2Department of Food Science and Technology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Korea; 3National Institute of Agricultural Biotechnology, RDA, Suwon 441-707, Korea; 4Department of Biology, Utah State University, Logan 84322-5305, U.S.A.

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Accepted 26 March 2006.

Root colonization by a plant-beneficial rhizobacterium, Pseudomonas chlororaphis O6, induces disease resistance in tobacco against leaf pathogens Erwinia carotovora subsp. carotovora SCC1, causing soft-rot, and Pseudomonas syringae pv. tabaci, causing wildfire. In order to identify the bacterial determinants involved in induced systemic resistance against plant diseases, extracellular components produced by the bacterium were fractionated and purified. Factors in the culture filtrate inducing systemic resistance were retained in the aqueous fraction rather than being partitioned into ethyl acetate. Fractionation on high-performance liquid chromatography followed by nuclear magnetic resonance mass spectrometry analysis identified the active compound as 2R, 3R-butanediol. 2R, 3R butanediol induced systemic resistance in tobacco to E. carotovora subsp. carotovora SCC1, but not to P. syringae pv. tabaci. Treatment of tobacco with the volatile 2R, 3R-butanediol enhanced aerial growth, a phenomenon also seen in plants colonized by P. chlororaphis O6. The isomeric form of the butanediol was important because 2S, 3S-butandiol did not affect the plant. The global sensor kinase, GacS, of P. chlororaphis O6 was a key regulator for induced systemic resistance against E. carotovora through regulation of 2R, 3R-butanediol production. This is the first report of the production of these assumed fermentation products by a pseudomonad and the role of the sensor kinase GacS in production of 2R, 3R-butanediol.

Additional keywords: promotion of plant growth , volatile compounds .

© 2006 The American Phytopathological Society