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Burkholderia phytofirmans PsJN induces long-term metabolic and transcriptional changes involved in Arabidopsis thaliana salt tolerance.

Pinedo I, Ledger T, Greve M, Poupin MJ - Front Plant Sci (2015)

Bottom Line: Among the general transcriptional effects of this bacterium, the expression pattern of important ion-homeostasis related genes was altered after short and long-term stress (Arabidopsis K(+) Transporter 1, High-Affinity K(+) Transporter 1, Sodium Hydrogen Exchanger 2, and Arabidopsis Salt Overly Sensitive 1).In all, the faster and stronger molecular changes induced by the inoculation suggest a PsJN-priming effect, which may explain the observed tolerance after short-term and sustained salt-stress in plants.This opens up new venues to study these relevant biological associations, as well as new approaches to a better understanding of the spatiotemporal mechanisms involved in stress tolerance in plants.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Bioingeniería, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez Santiago, Chile.

ABSTRACT
Salinity is one of the major limitations for food production worldwide. Improvement of plant salt-stress tolerance using plant-growth promoting rhizobacteria (PGPR) has arisen as a promising strategy to help overcome this limitation. However, the molecular and biochemical mechanisms controlling PGPR/plant interactions under salt-stress remain unclear. The main objective of this study was to obtain new insights into the mechanisms underlying salt-stress tolerance enhancement in the salt-sensitive Arabidopsis thaliana Col-0 plants, when inoculated with the well-known PGPR strain Burkholderia phytofirmans PsJN. To tackle this, different life history traits, together with the spatiotemporal accumulation patterns for key metabolites and salt-stress related transcripts, were analyzed in inoculated plants under short and long-term salt-stress. Inoculated plants displayed faster recovery and increased tolerance after sustained salt-stress. PsJN treatment accelerated the accumulation of proline and transcription of genes related to abscisic acid signaling (Relative to Dessication, RD29A and RD29B), ROS scavenging (Ascorbate Peroxidase 2), and detoxification (Glyoxalase I 7), and down-regulated the expression of Lipoxygenase 2 (related to jasmonic acid biosynthesis). Among the general transcriptional effects of this bacterium, the expression pattern of important ion-homeostasis related genes was altered after short and long-term stress (Arabidopsis K(+) Transporter 1, High-Affinity K(+) Transporter 1, Sodium Hydrogen Exchanger 2, and Arabidopsis Salt Overly Sensitive 1). In all, the faster and stronger molecular changes induced by the inoculation suggest a PsJN-priming effect, which may explain the observed tolerance after short-term and sustained salt-stress in plants. This study provides novel information about possible mechanisms involved in salt-stress tolerance induced by PGPR in plants, showing that certain changes are maintained over time. This opens up new venues to study these relevant biological associations, as well as new approaches to a better understanding of the spatiotemporal mechanisms involved in stress tolerance in plants.

No MeSH data available.


Related in: MedlinePlus

Effect of B. phytofirmans PsJN on A. thaliana salt-stress related genes transcription after long-term exposure to salt stress. Quantitative RT-PCR determinations of relative expression levels of the genes: AKT1; NHX2; SOS1; HKT1, and GLYI7, in new (A) and old leaves (B) of A. thaliana plants treated with or without strain PsJN, and transplanted at 11 DAS to soil. After 7 days of acclimation plant were irrigated with water with or without addition of 150 mM NaCl/15 mM CaCl2. RNA was extracted 35 days after transplantation (46 DAS). Data are means ± 1 SE of at least three biological replicates. Different letters indicate significant differences between treatments (Two-way ANOVA, p < 0.05; Bonferroni test, P < 0.05).
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Figure 7: Effect of B. phytofirmans PsJN on A. thaliana salt-stress related genes transcription after long-term exposure to salt stress. Quantitative RT-PCR determinations of relative expression levels of the genes: AKT1; NHX2; SOS1; HKT1, and GLYI7, in new (A) and old leaves (B) of A. thaliana plants treated with or without strain PsJN, and transplanted at 11 DAS to soil. After 7 days of acclimation plant were irrigated with water with or without addition of 150 mM NaCl/15 mM CaCl2. RNA was extracted 35 days after transplantation (46 DAS). Data are means ± 1 SE of at least three biological replicates. Different letters indicate significant differences between treatments (Two-way ANOVA, p < 0.05; Bonferroni test, P < 0.05).

Mentions: To determine if treatment with B. phytofirmans PsJN had long-term effects on the transcription of the ion transporters genes AKT1, NHX2, SOS1, and HKT1, plants were treated as described in the “Materials and Methods” section. For RNA extraction, the oldest and the newest leaves of each plant were selected, and RNA extractions were performed at a point were salt-stress had not stopped plant growth but stress signs were noted (46 DAS, Figure 3). As noticed before, AKT1 transcript accumulation was up-regulated by PsJN treatment both in new and old leaves at 35 days after stress (Figures 7A,B). The gene was up-regulated also by salt-stress only in old leaves (Figure 7B). The vacuolar transporter NHX2, showed an up-regulation due to salinity in new leaves. Interestingly, a stronger and significant up-regulation was observed when plants were inoculated with strain PsJN (Figure 7A). In old leaves this gene was similarly down-regulated by bacteria and salt-stress (Figure 7B). SOS1 expression was not altered in old leaves and PsJN up-regulated this gene in new leaves in non-stressed plants (Figure 7A). HKT1 transcript level, consistent with what was observed before, only depended on the effect of salinity that significantly down-regulated this gene, both in new and old leaves (Figures 7A,B). Finally, the expression of some of the early-stress responsive genes was analyzed after long-term exposure to stress. Expression of RD29B, PDF1.2, and LOX2 was not affected by salinity or PsJN inoculation at this time in new leaves (Supplementary Figure S3) and was not detected in old leaves (data not-shown). The detoxification gene, GLYI7, was up-regulated by salinity and not by PsJN in new leaves (Figure 7A). Notably, in old leaves, salinity also produced an up-regulation of the gene, but this effect was significantly lower when plants were treated with strain PsJN (Figure 7B).


Burkholderia phytofirmans PsJN induces long-term metabolic and transcriptional changes involved in Arabidopsis thaliana salt tolerance.

Pinedo I, Ledger T, Greve M, Poupin MJ - Front Plant Sci (2015)

Effect of B. phytofirmans PsJN on A. thaliana salt-stress related genes transcription after long-term exposure to salt stress. Quantitative RT-PCR determinations of relative expression levels of the genes: AKT1; NHX2; SOS1; HKT1, and GLYI7, in new (A) and old leaves (B) of A. thaliana plants treated with or without strain PsJN, and transplanted at 11 DAS to soil. After 7 days of acclimation plant were irrigated with water with or without addition of 150 mM NaCl/15 mM CaCl2. RNA was extracted 35 days after transplantation (46 DAS). Data are means ± 1 SE of at least three biological replicates. Different letters indicate significant differences between treatments (Two-way ANOVA, p < 0.05; Bonferroni test, P < 0.05).
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Related In: Results  -  Collection

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Figure 7: Effect of B. phytofirmans PsJN on A. thaliana salt-stress related genes transcription after long-term exposure to salt stress. Quantitative RT-PCR determinations of relative expression levels of the genes: AKT1; NHX2; SOS1; HKT1, and GLYI7, in new (A) and old leaves (B) of A. thaliana plants treated with or without strain PsJN, and transplanted at 11 DAS to soil. After 7 days of acclimation plant were irrigated with water with or without addition of 150 mM NaCl/15 mM CaCl2. RNA was extracted 35 days after transplantation (46 DAS). Data are means ± 1 SE of at least three biological replicates. Different letters indicate significant differences between treatments (Two-way ANOVA, p < 0.05; Bonferroni test, P < 0.05).
Mentions: To determine if treatment with B. phytofirmans PsJN had long-term effects on the transcription of the ion transporters genes AKT1, NHX2, SOS1, and HKT1, plants were treated as described in the “Materials and Methods” section. For RNA extraction, the oldest and the newest leaves of each plant were selected, and RNA extractions were performed at a point were salt-stress had not stopped plant growth but stress signs were noted (46 DAS, Figure 3). As noticed before, AKT1 transcript accumulation was up-regulated by PsJN treatment both in new and old leaves at 35 days after stress (Figures 7A,B). The gene was up-regulated also by salt-stress only in old leaves (Figure 7B). The vacuolar transporter NHX2, showed an up-regulation due to salinity in new leaves. Interestingly, a stronger and significant up-regulation was observed when plants were inoculated with strain PsJN (Figure 7A). In old leaves this gene was similarly down-regulated by bacteria and salt-stress (Figure 7B). SOS1 expression was not altered in old leaves and PsJN up-regulated this gene in new leaves in non-stressed plants (Figure 7A). HKT1 transcript level, consistent with what was observed before, only depended on the effect of salinity that significantly down-regulated this gene, both in new and old leaves (Figures 7A,B). Finally, the expression of some of the early-stress responsive genes was analyzed after long-term exposure to stress. Expression of RD29B, PDF1.2, and LOX2 was not affected by salinity or PsJN inoculation at this time in new leaves (Supplementary Figure S3) and was not detected in old leaves (data not-shown). The detoxification gene, GLYI7, was up-regulated by salinity and not by PsJN in new leaves (Figure 7A). Notably, in old leaves, salinity also produced an up-regulation of the gene, but this effect was significantly lower when plants were treated with strain PsJN (Figure 7B).

Bottom Line: Among the general transcriptional effects of this bacterium, the expression pattern of important ion-homeostasis related genes was altered after short and long-term stress (Arabidopsis K(+) Transporter 1, High-Affinity K(+) Transporter 1, Sodium Hydrogen Exchanger 2, and Arabidopsis Salt Overly Sensitive 1).In all, the faster and stronger molecular changes induced by the inoculation suggest a PsJN-priming effect, which may explain the observed tolerance after short-term and sustained salt-stress in plants.This opens up new venues to study these relevant biological associations, as well as new approaches to a better understanding of the spatiotemporal mechanisms involved in stress tolerance in plants.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Bioingeniería, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez Santiago, Chile.

ABSTRACT
Salinity is one of the major limitations for food production worldwide. Improvement of plant salt-stress tolerance using plant-growth promoting rhizobacteria (PGPR) has arisen as a promising strategy to help overcome this limitation. However, the molecular and biochemical mechanisms controlling PGPR/plant interactions under salt-stress remain unclear. The main objective of this study was to obtain new insights into the mechanisms underlying salt-stress tolerance enhancement in the salt-sensitive Arabidopsis thaliana Col-0 plants, when inoculated with the well-known PGPR strain Burkholderia phytofirmans PsJN. To tackle this, different life history traits, together with the spatiotemporal accumulation patterns for key metabolites and salt-stress related transcripts, were analyzed in inoculated plants under short and long-term salt-stress. Inoculated plants displayed faster recovery and increased tolerance after sustained salt-stress. PsJN treatment accelerated the accumulation of proline and transcription of genes related to abscisic acid signaling (Relative to Dessication, RD29A and RD29B), ROS scavenging (Ascorbate Peroxidase 2), and detoxification (Glyoxalase I 7), and down-regulated the expression of Lipoxygenase 2 (related to jasmonic acid biosynthesis). Among the general transcriptional effects of this bacterium, the expression pattern of important ion-homeostasis related genes was altered after short and long-term stress (Arabidopsis K(+) Transporter 1, High-Affinity K(+) Transporter 1, Sodium Hydrogen Exchanger 2, and Arabidopsis Salt Overly Sensitive 1). In all, the faster and stronger molecular changes induced by the inoculation suggest a PsJN-priming effect, which may explain the observed tolerance after short-term and sustained salt-stress in plants. This study provides novel information about possible mechanisms involved in salt-stress tolerance induced by PGPR in plants, showing that certain changes are maintained over time. This opens up new venues to study these relevant biological associations, as well as new approaches to a better understanding of the spatiotemporal mechanisms involved in stress tolerance in plants.

No MeSH data available.


Related in: MedlinePlus