Abstract
Several plant growth-promoting rhizobacteria (PGPR) are known to improve plant tolerance to multiple stresses, including low temperatures. However, mechanisms underlying this protection are still poorly understood. The aim of this study was to evaluate the role of the endophytic PGPR, Burkholderia phytofirmans strain PsJN (Bp PsJN), on Arabidopsis thaliana cold tolerance using photosynthesis parameters as physiological markers. Under standard conditions, our results indicated that Bp PsJN inoculation led to growth promotion of Arabidopsis plants without significant modification on photosynthesis parameters and chloroplast organization. However, bacterial colonization induced a cell wall strengthening in the mesophyll. Impact of inoculation modes (either on seeds or by soil irrigation) and their effects overnight at 0, -1, or -3°C, were investigated by following photosystem II (PSII) activity and gas exchanges. Following low temperatures stress, a decrease of photosynthesis parameters was observed. In addition, during three consecutive nights or days at -1°C, PSII activity was monitored. Pigment contents, RuBisCO protein abundance, expression of several genes including RbcS, RbcL, CBF1, CBF2, CBF3, ICE1, COR15a, and COR78 were evaluated at the end of exposure. To assess the impact of the bacteria on cell ultrastructure under low temperatures, microscopic observations were achieved. Results indicated that freezing treatment induced significant changes in PSII activity as early as the first cold day, whereas the same impact on PSII activity was observed only during the third cold night. The significant effects conferred by PsJN were differential accumulation of pigments, and reduced expression of RbcL and COR78. Microscopical observations showed an alteration/disorganization in A. thaliana leaf mesophyll cells independently of the freezing treatments. The presence of bacteria during the three successive nights or days did not significantly improved A. thaliana responses but prevented the plasmalemma disruption under freezing stress.
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Claims 12
Claim · model-written summary
PsJN inoculation promoted Arabidopsis growth under standard conditions.
- Taxon
- Arabidopsis plantse0
- Treatment
- Bp PsJN inoculatione0
- Interactor
- Burkholderia phytofirmans PsJNParaburkholderia phytofirmans PsJNt0symbiont
- Outcome
- growth promotione0
- Direction
- promotione0
Not reportedComparator
Verbatim
e0“Under standard conditions, our results indicated that Bp PsJN inoculation led to growth promotion of Arabidopsis plants”
t0“Burkholderia phytofirmans PsJN reduces impact of freezing temperatures on photosynthesis in Arabidopsis thaliana”
Claim · model-written summary
PsJN inoculation did not significantly modify photosynthesis parameters under standard conditions.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Treatment
- Bp PsJN inoculatione1
- Outcome
- photosynthesis parameters and chloroplast organizatione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“without significant modification on photosynthesis parameters and chloroplast organization”
e1“Bp PsJN inoculation”
t0“Arabidopsis thaliana”
Claim · model-written summary
Bacterial colonization strengthened mesophyll cell walls.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- mesophylle0
- Treatment
- bacterial colonizatione0
- Outcome
- cell wall strengtheninge0
- Direction
- strengtheninge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“bacterial colonization induced a cell wall strengthening in the mesophyll”
t0“Arabidopsis thaliana”
Claim · model-written summary
Low temperature stress decreased photosynthesis parameters.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- low temperatures stresse0
- Outcome
- photosynthesis parameterse0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Following low temperatures stress, a decrease of photosynthesis parameters was observed”
t0“Arabidopsis thaliana”
Claim · model-written summary
Freezing significantly changed PSII activity on the first cold day.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- freezing treatmente0
- Outcome
- PSII activitye0
- Qualifier
- as early as the first cold daye0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“freezing treatment induced significant changes in PSII activity as early as the first cold day”
t0“Arabidopsis thaliana”
Claim · model-written summary
The same freezing impact on PSII activity appeared only on the third cold night.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- freezing treatmente1
- Outcome
- PSII activitye0
- Qualifier
- only during the third cold nighte0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the same impact on PSII activity was observed only during the third cold night”
e1“freezing treatment induced significant changes”
t0“Arabidopsis thaliana”
Claim · model-written summary
PsJN conferred differential pigment accumulation.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- PsJNe0
- Outcome
- accumulation of pigmentse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The significant effects conferred by PsJN were differential accumulation of pigments”
t0“Arabidopsis thaliana”
Claim · model-written summary
PsJN reduced RbcL expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- PsJNe0
- Gene
- RbcLe0
- Outcome
- expression of RbcLe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The significant effects conferred by PsJN were differential accumulation of pigments, and reduced expression of RbcL and COR78”
t0“Arabidopsis thaliana”
Claim · model-written summary
PsJN reduced COR78 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- PsJNe0
- Gene
- COR78e0
- Outcome
- expression of RbcL and COR78e0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The significant effects conferred by PsJN were differential accumulation of pigments, and reduced expression of RbcL and COR78”
t0“Arabidopsis thaliana”
Claim · model-written summary
Arabidopsis leaf mesophyll cells showed alteration or disorganization independent of freezing treatments.
- Taxon
- A. thalianaArabidopsis thalianae0
- Organ / stage
- leaf mesophyll cellse0
- Outcome
- alteration/disorganization in A. thaliana leaf mesophyll cellse0
- Qualifier
- independently of the freezing treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an alteration/disorganization in A. thaliana leaf mesophyll cells independently of the freezing treatments”
Claim · model-written summary
Bacterial presence did not significantly improve Arabidopsis responses during three successive cold nights or days.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- presence of bacteriae0
- Outcome
- A. thaliana responsese0
- Qualifier
- during the three successive nights or dayse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of bacteria during the three successive nights or days did not significantly improved A. thaliana responses”
Claim · model-written summary
Bacterial presence prevented plasmalemma disruption under freezing stress.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- presence of bacteriae1
- Outcome
- plasmalemma disruptione0
- Direction
- preventede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“prevented the plasmalemma disruption under freezing stress”
e1“The presence of bacteria”
t0“Arabidopsis thaliana”
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