Isolation and Characterization of Mutants of the Plant Growth-Promoting Rhizobacterium Pseudomonas putida GR12-2 That Overproduce Indoleacetic Acid |
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Authors: | Hong Xie JJ Pasternak Bernard R Glick |
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Institution: | (1) Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 , CA |
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Abstract: | Following transposon Tn5 mutagenesis of the plant growth-promoting rhizobacterium Pseudomonas putida GR12-2, mutants that were able to grow in the presence of the tryptophan analog 5-fluorotryptophan were selected. Seven of
the 50 5-fluorotryptophan-resistant mutants overproduced the phytohormone indoleacetic acid (IAA). Of these seven mutants,
the highest level of IAA was observed with strain P. putida GR12-2/aux1, which produced four times the amount of indoleacetic acid synthesized by the wild-type strain. Strain P. putida GR12-2/aux1, in contrast to the wild type, lost the ability to stimulate the elongation of the roots of canola seedlings under gnotobiotic
conditions. The growth rate, siderophore production, and 1-aminocyclopropane-1-carboxylate deaminase activity of mutant strain
P. putida GR12-2/aux1 were identical to those of the wild-type strain. The role of IAA in the mechanism of plant growth stimulation by P. putida GR12-2 and other plant growth-promoting rhizobacteria is discussed. |
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