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Cytokinin production by plant growth promoting rhizobacteria and selected mutants

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One of the proposed mechanisms by which rhizobacteria enhance plant growth is through the production of plant growth regulators. Five plant growth promoting rhizobacterial (PGPR) strains produced the cytokinin dihydrozeatin riboside (DHZR) in pure culture. Cytokinin production by Pseudomonas fluorescens G20–18, a rifampicin-resistant mutant (RIF), and two TnphoA-derived mutants (CNT1, CNT2), with reduced capacity to synthesize cytokinins, was further characterized in pure culture using immunoassay and thin layer chromatography. G20–18 produced higher amounts of three cytokinins, isopentenyl adenosine (IPA), trans-zeatin ribose (ZR), and DHZR than the three mutants during stationary phase. IPA was the major metabolite produced, but the proportion of ZR and DHZR accumulated by CNT1 and CNT2 increased with time. No differences were observed between strain G20–18 and the mutants in the amounts of indole acetic acid synthesized, nor were gibberellins detected in supernatants of any of the strains. Addition of 10–5 M adenine increased cytokinin production in 96- and 168-h cultures of strain G20–18 by approximately 67%. G20–18 and the mutants CNT1 and CNT2 may be useful for determination of the role of cytokinin production in plant growth promotion by PGPR.Key words: cytokinins, plant growth regulation, Pseudomonas fluorescens, rhizobacteria, plant growth promoting rhizobacteria (PGPR).

Un des mécanismes proposés pour expliquer la stimulation de la croissance des plantes par les rhizobactéries passe par la production de régulateurs de la croissance végétale. Cinq souches de rhizobactéries stimulant la croissance des plantes (RSCP) ont produit la cytokinine dihydrizéatine riboside (DHZR) en culture pure. La production de cytokinines par Pseudomonas fluorescens G20–18, un mutant résistant à la rifampicine (RIF), et par deux mutants dérivés de TnphoA (CNT1, CNT2) ayant une capacité réduite à synthétiser des cytokinines, a été caractérisée plus en détail en culture pure par des immuno-essais et des analyses de chromatographie en couches fines. G20–18 a produit des quantités plus élevées de trois cytokinines, isopentenyl adénosine (IPA), trans-zéatine ribose (ZR) et DHZR, que les trois mutants au cours de la phase stationnaire. L'IPA fut le principal métabolite produit, mais la proportion de ZR et de DHZR accumulé par CNT1 et CNT2 augmenta avec le temps. Aucune différence ne fut observée entre la souche G20–18 et les mutants sur le plan des quantités d'acide indole acétique synthétisées. Aucune gibberelline ne fut détectée dans les surnageants des souches. L'ajout de 10–5 M d'adénine a augmenté d'environ 67% la production de cytokinines dans des cultures de 96 et 168 h de la souche G20–18. La souche G20–18 et les mutants CNT1 et CNT2 pourraient s'avérer utiles afin de déterminer le rôle de la production de cytokinines dans la stimulation de la croissance végétale par les RSCP.Mots clés : cytokinines, régulation de la croissance des plantes, Pseudomonas fluorescens, rhizobactéries, rhizobactéries stimulant la croissance des plantes (RSCP).[Traduit par la Rédaction]

Keywords: Pseudomonas fluorescens; cytokinines; cytokinins; plant growth promoting rhizobacteria (PGPR); plant growth regulation; rhizobacteria; rhizobactéries; rhizobactéries stimulant la croissance des plantes (RSCP); régulation de la croissance des plantes

Document Type: Research Article

Publication date: May 1, 2001

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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