Root Colonization and Quorum Sensing are the Driving forces of Plant Growth Promoting Rhizobacteria (pgpr) for Growth Promotion

Early seedling root growth of the nonlegumes canola (Brassica campestris cv. Tobin, Brassica napus cv. Westar) and lettuce (Lactuca saliva cv. Grand Rapids) was significantly promoted by inoculation of seeds with certain strains of Rhizobium leguminosarum, including nitrogen- and nonnitrogen-fixing derivatives under gnotobiotic conditions. The growfh-promotive effect appears to be direct, with possible involvement of the plant growth regulators indole-3-acetic acid and cytokinin. Auxotrophic Rhizobium mutants requiring tryptophan or adenosine (precursors for indole-3-acetic acid and cytokinin synthesis, respectively) did not promote growth to the extent of the parent strain. The findings of this study demonstrate a new facet of the Rhizobium–plant relationship and that Rhizobium leguminosarum can be considered a plant growth-promoting rhizobacterium (PGPR).Key words: Rhizobium, plant growth-promoting rhizobacteria, PGPR, indole-3-acetic acid, cytokinin, roots, auxotrophic mutants.

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Quorum Sensing and Indole-3-Acetic Acid Degradation Play a Role in Colonization and Plant Growth Promotion of Arabidopsis thaliana by Burkholderia phytofirmans PsJN

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-10-12-0241-r ◽

2013 ◽

Vol 26 (5) ◽

pp. 546-553 ◽

Cited By ~ 85

Author(s):

Ana Zúñiga ◽

María Josefina Poupin ◽

Raúl Donoso ◽

Thomas Ledger ◽

Nicolás Guiliani ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Acetic Acid ◽

Quorum Sensing ◽

Plant Growth ◽

Growth Promotion ◽

Auxin Signaling ◽

Plant Growth Promoting ◽

Growth Promoting ◽

Indole 3 Acetic Acid ◽

Burkholderia Phytofirmans Psjn

Although not fully understood, molecular communication in the rhizosphere plays an important role regulating traits involved in plant–bacteria association. Burkholderia phytofirmans PsJN is a well-known plant-growth-promoting bacterium, which establishes rhizospheric and endophytic colonization in different plants. A competent colonization is essential for plant-growth-promoting effects produced by bacteria. Using appropriate mutant strains of B. phytofirmans, we obtained evidence for the importance of N-acyl homoserine lactone-mediated (quorum sensing) cell-to-cell communication in efficient colonization of Arabidopsis thaliana plants and the establishment of a beneficial interaction. We also observed that bacterial degradation of the auxin indole-3-acetic acid (IAA) plays a key role in plant-growth-promoting traits and is necessary for efficient rhizosphere colonization. Wildtype B. phytofirmans but not the iacC mutant in IAA mineralization is able to restore promotion effects in roots of A. thaliana in the presence of exogenously added IAA, indicating the importance of this trait for promoting primary root length. Using a transgenic A. thaliana line with suppressed auxin signaling (miR393) and analyzing the expression of auxin receptors in wild-type inoculated plants, we provide evidence that auxin signaling in plants is necessary for the growth promotion effects produced by B. phytofirmans. The interplay between ethylene and auxin signaling was also confirmed by the response of the plant to a 1-aminocyclopropane-1-carboxylate deaminase bacterial mutant strain.

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Colonization and growth promotion of outplanted spruce seedlings pre-inoculated with plant growth-promoting rhizobacteria in the greenhouse

Canadian Journal of Forest Research ◽

10.1139/x00-010 ◽

2000 ◽

Vol 30 (6) ◽

pp. 845-854 ◽

Cited By ~ 19

Author(s):

Masahiro Shishido ◽

Christopher P Chanway

Keyword(s):

Plant Growth ◽

Seedling Growth ◽

Picea Glauca ◽

Growth Promotion ◽

Plant Growth Promoting Rhizobacteria ◽

Population Declines ◽

Growth Responses ◽

Relative Growth Rates ◽

Plant Growth Promoting ◽

Growth Promoting

Seeds of two hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) ecotypes were inoculated with one of six plant growth-promoting rhizobacteria (PGPR) strains previously shown to be able to stimulate spruce growth in controlled environments. The resulting seedlings were grown in the greenhouse for 17 weeks before outplanting at four reforestation sites. Inoculation with five of the six strains caused significant seedling growth promotion in the greenhouse, which necessitated analysis of relative growth rates (RGR) to evaluate seedling performance in the field. Four months after outplanting, most strains enhanced spruce shoot or root RGRs in the field, but seedling growth responses were strain specific. For example, Pseudomonas strain Ss2-RN significantly increased both shoot and root RGRs by 10-234% at all sites, but increases of 28-70% were most common. In contrast, Bacillus strain S20-R was ineffective at all outplanting sites. In addition, seedlings inoculated with four of the six strains had significantly less shoot injury than control seedlings at all sites. Evaluation of root colonization by PGPR indicated that bacterial population declines were not related to spruce growth response variability in the field. Our results indicate that once plant growth promotion is induced in the greenhouse, seedling RGR can increase by more than 100% during the first growing season in the field. However RGR increases of 21-47% were more common and may be more representative of the magnitude of biomass increases that can result from PGPR inoculation.

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Growth Promotion of Maize (Zea maysL.) by Plant-Growth-Promoting Rhizobacteria under Field Conditions

Communications in Soil Science and Plant Analysis ◽

10.1080/00103624.2012.666302 ◽

2012 ◽

Vol 43 (9) ◽

pp. 1263-1272 ◽

Cited By ~ 6

Author(s):

Ahmad Gholami ◽

Atena Biyari ◽

Manoochehr Gholipoor ◽

Hadi Asadi Rahmani

Keyword(s):

Plant Growth ◽

Growth Promotion ◽

Plant Growth Promoting Rhizobacteria ◽

Field Conditions ◽

Plant Growth Promoting ◽

Growth Promoting

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Characterization of Selected Plant Growth-Promoting Rhizobacteria and Their Non-Host Growth Promotion Effects

Microbiology Spectrum ◽

10.1128/spectrum.00279-21 ◽

2021 ◽

Author(s):

Di Fan ◽

Donald L. Smith

Keyword(s):

Arabidopsis Thaliana ◽

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Plant Growth Promoting Rhizobacteria ◽

Content Type ◽

Host Growth ◽

Plant Growth Promoting ◽

Growth Promoting

There are pressing needs to reduce the use of agrochemicals, and PGPR are receiving increasing interest in plant growth promotion and disease protection. This study follows up our previous report that the four newly isolated rhizobacteria promote the growth of Arabidopsis thaliana .

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