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Galactinol Is a Signaling Component of the Induced Systemic Resistance Caused by Pseudomonas chlororaphis O6 Root Colonization

December 2008 , Volume 21 , Number  12
Pages  1,643 - 1,653

Mi Seong Kim,1 Song Mi Cho,2 Eun Young Kang,1 Yang Ju Im,1 Hoon Hwangbo,1 Young Cheol Kim,1 Choong-Min Ryu,3 Kwang Yeol Yang,1 Gap Chae Chung,1 and Baik Ho Cho1

1Agricultural Plant Stress Research Center, Biotechnology Research Institute, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea; 2Department of Floriculture, Chunnam Techno College, Jeonnam 516-991, Republic of Korea; 3Systems Microbiology Research Center, KRIBB, Daejon 305-333, Republic of Korea

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Accepted 25 July 2008.

Root colonization by Pseudomonas chlororaphis O6 in cucumber elicited an induced systemic resistance (ISR) against Corynespora cassiicola. In order to gain insight into O6-mediated ISR, a suppressive subtractive hybridization technique was applied and resulted in the isolation of a cucumber galactinol synthase (CsGolS1) gene. The transcriptional level of CsGolS1 and the resultant galactinol content showed an increase several hours earlier under O6 treatment than in the water control plants following C. cassiicola challenge, whereas no difference was detected in the plants without a pathogen challenge. The CsGolS1-overexpressing transgenic tobacco plants demonstrated constitutive resistance against the pathogens Botrytis cinerea and Erwinia carotovora, and they also showed an increased accumulation in galactinol content. Pharmaceutical application of galactinol enhanced the resistance against pathogen infection and stimulated the accumulation of defense-related gene transcripts such as PR1a, PR1b, and NtACS1 in wild-type tobacco plants. Both the CsGolS1-overexpressing transgenic plants and the galactinol-treated wild-type tobacco plants also demonstrated an increased tolerance to drought and high salinity stresses.

© 2008 The American Phytopathological Society