Title: Phytostimulatory effect of Azospirillum brasilense wild type and mutant strains altered in IAA production on wheat
Authors: Dobbelaere, Sofie ×
Croonenborghs, Anja
Thys, Amber
Vande Broek, Ann
Vanderleyden, Jozef #
Issue Date: 1999
Publisher: Kluwer academic publ
Series Title: Plant and soil vol:212 issue:2 pages:155-164
Abstract: Auxin production by Azospirillum is believed to play a major role in the observed plant growth promoting effect. By using different genetically modified strains, the contribution of auxin biosynthesis by A. brasilense in altering root morphology was evaluated in a plate assay. Inoculation with the wild type strains A. brasilense Sp245 and Sp7 resulted in a strong decrease in root length and increase in root hair formation. This effect was abolished when inoculating with an ipdC mutant of A. brasilense. The ipdC gene encodes a key enzyme in the IPyA pathway of IAA synthesis by A. brasilense. On the other hand, the observed auxin effect was further enhanced by adding tryptophan, a precursor of IAA, to the plates and could be mimicked by replacing the Azospirillum cells by a particular concentration of IAA. Furthermore, particular mutants (rpoN, scrp) and transconjugants (extra copy of ipdC) of A. brasilense were tested in the plate assay. Together, these results confirm the important role of IAA produced by Azospirillum in altering root morphology and illustrate the power of combining genetic tools and bioassays to elucidate the mechanism of a beneficial Azospirillum-plant interaction.
ISSN: 0032-079X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre of Microbial and Plant Genetics
× corresponding author
# (joint) last author

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