Abstract
BACKGROUND AND AIMS: The objective of the study was to assess the impact of elevated CO2 in interaction with rhizobial strains on freezing tolerance and cold-induced molecular changes in alfalfa. METHODS: Alfalfa inoculated with two different strains of rhizobium (A2 and NRG34) was grown and cold acclimated (2 weeks at 2 degrees C) under either 400 (ambient) or 800 micromol mol(-1) (elevated) CO2. KEY RESULTS: Plants acclimated under 400 micromol mol(-1) CO2 were more freezing tolerant than those maintained under 800 micromol mol(-1). Cryoprotective sugars typically linked with the acquisition of freezing tolerance such as sucrose, stachyose and raffinose increased in roots in response to low temperature but did not differ between CO2 treatments. Similarly high CO2 did not alter the expression of many cold-regulated (COR) genes although it significantly increased the level of transcripts encoding a COR gene homologous to glyceraldehyde-3-phosphate-dehydrogenase (GAPDH). A significant effect of rhizobial strain was observed on both freezing tolerance and gene expression. Plants of alfalfa inoculated with strain A2 were more freezing tolerant than those inoculated with strain NRG34. Transcripts of COR genes homologous to a pathogenesis-related protein (PR-10) and to a nuclear-targeted protein were markedly enhanced in roots of alfalfa inoculated with strain A2 as compared with strain NRG34. Transcripts encoding the vegetative storage proteins (VSPs) beta-amylase and chitinase were more abundant in roots of non-acclimated plants inoculated with strain NRG34 than with strain A2. CONCLUSIONS: Taken together, the results suggest that elevated CO2 stimulates plant growth and reduces freezing tolerance. The acquisition of cold tolerance is also influenced by the rhizobial strain, as indicated by lower levels of expression of COR genes and sustained accumulation of VSP-encoding transcripts in alfalfa inoculated with strain NRG34 as compared with strain A2.
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Claims 9
Claim · model-written summary
Alfalfa cold-acclimated under ambient CO2 was more freezing tolerant than under elevated CO2.
- Taxon
- alfalfa
Medicago sativae1 - Treatment
- 800 micromol mol(-1)e0
- Outcome
- freezing tolerante0
- Direction
- moree0
- Comparator
- 400 micromol mol(-1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants acclimated under 400 micromol mol(-1) CO2 were more freezing tolerant than those maintained under 800 micromol mol(-1)”
e1“cold-induced molecular changes in alfalfa”
Claim · model-written summary
Low temperature increased sucrose, stachyose and raffinose in alfalfa roots.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- rootse0
- Treatment
- low temperaturee0
- Outcome
- sucrose, stachyose and raffinosee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sucrose, stachyose and raffinose increased in roots in response to low temperature”
e1“cold-induced molecular changes in alfalfa”
Claim · model-written summary
Alfalfa root sucrose, stachyose and raffinose did not differ between CO2 treatments.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- rootse0
- Treatment
- CO2 treatmentse0
- Outcome
- sucrose, stachyose and raffinosee0
- Direction
- did not differe0
- Comparator
- CO2 treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sucrose, stachyose and raffinose increased in roots in response to low temperature but did not differ between CO2 treatments”
e1“cold-induced molecular changes in alfalfa”
Claim · model-written summary
High CO2 did not alter expression of many cold-regulated genes in alfalfa.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- high CO2e0
- Outcome
- expression of many cold-regulated (COR) genese0
- Direction
- did not altere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high CO2 did not alter the expression of many cold-regulated (COR) genes”
e1“cold-induced molecular changes in alfalfa”
Claim · model-written summary
High CO2 significantly increased alfalfa transcript levels for a GAPDH-homologous COR gene.
- Taxon
- alfalfaMedicago sativae2
- Treatment
- high CO2e1
- Gene
- COR gene homologous to glyceraldehyde-3-phosphate-dehydrogenase (GAPDH)e0
- Outcome
- level of transcripts encoding a COR gene homologous to glyceraldehyde-3-phosphate-dehydrogenase (GAPDH)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it significantly increased the level of transcripts encoding a COR gene homologous to glyceraldehyde-3-phosphate-dehydrogenase (GAPDH)”
e1“high CO2 did not alter”
e2“cold-induced molecular changes in alfalfa”
Claim · model-written summary
Alfalfa inoculated with strain A2 was more freezing tolerant than with NRG34.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- inoculated with strain A2e0
- Outcome
- freezing tolerante0
- Direction
- moree0
- Comparator
- inoculated with strain NRG34e0
RhizobiumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants of alfalfa inoculated with strain A2 were more freezing tolerant than those inoculated with strain NRG34”
e1“two different strains of rhizobium (A2 and NRG34)”
Claim · model-written summary
A2 inoculation markedly enhanced alfalfa root transcripts for PR-10 and a nuclear-targeted COR protein relative to NRG34.
- Taxon
- alfalfaMedicago sativae0
- Organ / stage
- rootse0
- Treatment
- inoculated with strain A2e0
- Outcome
- Transcripts of COR genes homologous to a pathogenesis-related protein (PR-10) and to a nuclear-targeted proteine0
- Direction
- enhancede0
- Comparator
- strain NRG34e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcripts of COR genes homologous to a pathogenesis-related protein (PR-10) and to a nuclear-targeted protein were markedly enhanced in roots of alfalfa inoculated with strain A2 as compared with strain NRG34”
e1“two different strains of rhizobium (A2 and NRG34)”
Claim · model-written summary
NRG34 inoculation increased beta-amylase and chitinase transcripts in non-acclimated alfalfa roots relative to A2.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- rootse0
- Treatment
- inoculated with strain NRG34e0
- Outcome
- Transcripts encoding the vegetative storage proteins (VSPs) beta-amylase and chitinasee0
- Direction
- more abundante0
- Comparator
- strain A2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcripts encoding the vegetative storage proteins (VSPs) beta-amylase and chitinase were more abundant in roots of non-acclimated plants inoculated with strain NRG34 than with strain A2”
e1“cold-induced molecular changes in alfalfa”
e2“two different strains of rhizobium (A2 and NRG34)”
Claim · model-written summary
The authors infer elevated CO2 stimulates alfalfa growth.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- elevated CO2e0
- Outcome
- plant growthe0
- Direction
- stimulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO2 stimulates plant growth and reduces freezing tolerance”
e1“cold-induced molecular changes in alfalfa”
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