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Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

Rudrappa T, Splaine RE, Biedrzycki ML, Bais HP - PLoS ONE (2008)

Bottom Line: Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots.The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM.Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America.

ABSTRACT
In the rhizosphere, plant roots cope with both pathogenic and beneficial bacterial interactions. The exometabolite production in certain bacterial species may regulate root growth and other root-microbe interactions in the rhizosphere. Here, we elucidated the role of cyanide production in pseudomonad virulence affecting plant root growth and other rhizospheric processes. Exposure of Arabidopsis thaliana Col-0 seedlings to both direct (with KCN) and indirect forms of cyanide from different pseudomonad strains caused significant inhibition of primary root growth. Further, we report that this growth inhibition was caused by the suppression of an auxin responsive gene, specifically at the root tip region by pseudomonad cyanogenesis. Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots. The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM. Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

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Related in: MedlinePlus

Direct and indirect effect of different doses (0–700 µM) cyanide on the growth of A. thaliana Col-0 seedling.The data shows the linear regression plots (A&B) shows the predicted (line) and experimental (dots) values of primary root length at different concentrations of KCN(B; r2 = 0.8581) and HCN (D; r2 = 0.779). Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
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pone-0002073-g003: Direct and indirect effect of different doses (0–700 µM) cyanide on the growth of A. thaliana Col-0 seedling.The data shows the linear regression plots (A&B) shows the predicted (line) and experimental (dots) values of primary root length at different concentrations of KCN(B; r2 = 0.8581) and HCN (D; r2 = 0.779). Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.

Mentions: Based on our earlier results, which showed a significantly higher cyanide ion accumulation in the cultures of P. aeruginosa PAO1/PA14 and P. fluorescens CHAO, we hypothesized that if the cyanide produced by the pseudomonad strains is responsible for primary root growth inhibition, exogenously supplied cyanide should also inhibit the A. thaliana Col-0 root growth. Consistent with our hypothesis, the plants exposed with both direct KCN and indirect (HCN) showed significant (P<0.05; n = 12) inhibition of the primary root growth of A. thaliana Col-0 seedlings (Figure 3A&B). The plot shows the linearity of the relationship between the predicted (line) and experimental (dots) values of primary root length and cyanide concentration (Figures 3A&B). Thus, all these results together conclusively established that the inhibition of A. thaliana Col-0 primary root growth by different strains of pseudomonads especially P. aeruginosa PAO1, PA14 and P. fluorescens CHAO is due to the production and release of cyanide. This result was also confirmed by the reduced inhibition of primary root growth by cyanide mutants of P. aeruginosa PAO6344 and P. fluorescens CHAO77 (Figures 1A&B).


Cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere.

Rudrappa T, Splaine RE, Biedrzycki ML, Bais HP - PLoS ONE (2008)

Direct and indirect effect of different doses (0–700 µM) cyanide on the growth of A. thaliana Col-0 seedling.The data shows the linear regression plots (A&B) shows the predicted (line) and experimental (dots) values of primary root length at different concentrations of KCN(B; r2 = 0.8581) and HCN (D; r2 = 0.779). Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2315799&req=5

pone-0002073-g003: Direct and indirect effect of different doses (0–700 µM) cyanide on the growth of A. thaliana Col-0 seedling.The data shows the linear regression plots (A&B) shows the predicted (line) and experimental (dots) values of primary root length at different concentrations of KCN(B; r2 = 0.8581) and HCN (D; r2 = 0.779). Data is the mean±SD of 12 replicates and the experiment was repeated on two independent occasions.
Mentions: Based on our earlier results, which showed a significantly higher cyanide ion accumulation in the cultures of P. aeruginosa PAO1/PA14 and P. fluorescens CHAO, we hypothesized that if the cyanide produced by the pseudomonad strains is responsible for primary root growth inhibition, exogenously supplied cyanide should also inhibit the A. thaliana Col-0 root growth. Consistent with our hypothesis, the plants exposed with both direct KCN and indirect (HCN) showed significant (P<0.05; n = 12) inhibition of the primary root growth of A. thaliana Col-0 seedlings (Figure 3A&B). The plot shows the linearity of the relationship between the predicted (line) and experimental (dots) values of primary root length and cyanide concentration (Figures 3A&B). Thus, all these results together conclusively established that the inhibition of A. thaliana Col-0 primary root growth by different strains of pseudomonads especially P. aeruginosa PAO1, PA14 and P. fluorescens CHAO is due to the production and release of cyanide. This result was also confirmed by the reduced inhibition of primary root growth by cyanide mutants of P. aeruginosa PAO6344 and P. fluorescens CHAO77 (Figures 1A&B).

Bottom Line: Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots.The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM.Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America.

ABSTRACT
In the rhizosphere, plant roots cope with both pathogenic and beneficial bacterial interactions. The exometabolite production in certain bacterial species may regulate root growth and other root-microbe interactions in the rhizosphere. Here, we elucidated the role of cyanide production in pseudomonad virulence affecting plant root growth and other rhizospheric processes. Exposure of Arabidopsis thaliana Col-0 seedlings to both direct (with KCN) and indirect forms of cyanide from different pseudomonad strains caused significant inhibition of primary root growth. Further, we report that this growth inhibition was caused by the suppression of an auxin responsive gene, specifically at the root tip region by pseudomonad cyanogenesis. Additionally, pseudomonad cyanogenesis also affected other beneficial rhizospheric processes such as Bacillus subtilis colonization by biofilm formation on A. thaliana Col-0 roots. The effect of cyanogenesis on B. subtilis biofilm formation was further established by the down regulation of important B. subtilis biofilm operons epsA and yqxM. Our results show, the functional significance of pseudomonad cyanogenesis in regulating multitrophic rhizospheric interactions.

Show MeSH
Related in: MedlinePlus