Abstract
Certain plant growth–promoting bacteria, such as Pseudomonas fluorescens 89B61 and Bacillus pumilus SE34, secreted high levels of indole-3-acetic acid (IAA) in tryptophan-amended medium in stationary phase as determined by chromogenic analysis and high-performance liquid chromatography. Two other growth-promoting strains, P. chlororaphis O6 and Serratia marcescens 90-166, did not produce these high levels of IAA. However, when the gacS mutant of P. chlororaphis O6 was grown in tryptophan-supplemented medium, IAA was detected in culture filtrates. IAA production by the gacS mutant in P. chlororaphis O6 was repressed in the tryptophan medium by complementation with the wild-type gacS gene. Thus, the global regulatory Gac system in P. chlororaphis O6 acts as a negative regulator of IAA production from trypophan.
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Acknowledgments
This work was supported by a grant from (1) the Korea Science and Engineering Foundation through the Agricultural Plant Stress Research Center (R11-2001-092-03008-0) at Chonnam National University and (2) the BioGreen 21 program, Rural Development Administration, Korea. It was also supported by funding from the Utah State Agricultural Research Station (Article No. 54322). We thank Dr. Choong-Min Ryu for critical comments on the manuscript and Dr. J. Kloepper for the gift of the PGRP strains.
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Kang, B.R., Yang, K.Y., Cho, B.H. et al. Production of Indole-3-Acetic Acid in the Plant-Beneficial Strain Pseudomonas chlororaphis O6 Is Negatively Regulated by the Global Sensor Kinase GacS. Curr Microbiol 52, 473–476 (2006). https://doi.org/10.1007/s00284-005-0427-x
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DOI: https://doi.org/10.1007/s00284-005-0427-x