H. Xie et al., ISOLATION AND CHARACTERIZATION OF MUTANTS OF THE PLANT GROWTH-PROMOTING RHIZOBACTERIUM PSEUDOMONAS-PUTIDA CR12-2 THAT OVERPRODUCE INDOLEACETIC-ACID, Current microbiology, 32(2), 1996, pp. 67-71
Following transposon Tn5 mutagenesis of the plant growth-promoting rhi
zobacterium Pseudomonas putida GR12-2, mutants that were able to grow
in the presence of the tryptophan analog 5-fluorotryptophan were selec
ted. 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 roo
ts of canola seedlings under gnotobiotic conditions. The growth rate,
siderophore production, and 1-aminocyclopropane-1-carboxylate deaminas
e activity of mutant strain P. putida GR12-2/aux1 were identical to th
ose 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-promoti
ng rhizobacteria is discussed.