Abstract
To investigate the sensitive site of antioxidant systems in chloroplast under cadmium stress and its consequence on reactive oxygen species production and action, the sub-organellar localization of chloroplast superoxide dismutases (SOD, EC 1.15.1.1) and ascorbic peroxidase (APX, EC 1.11.1.11) isoenzymes and changes of enzymes activities under cadmium stress were investigated in tomato seedlings. Two APX isoforms, one thylakoid-bound and one stromal, were detected. Cd at 50 microM induced a moderate increase of SOD activities but a rapid inactivation of both APX isoenzymes. APX inactivation was mainly related to the decrease of ascorbate concentration, as supported by in vitro treatment of exogenous ascorbate and APX kinetic properties under Cd stress. H2O2 accumulation in chloroplast, as a consequence of APX inactivation, was associated with a 60% loss of Rubisco (EC 4.1.1.39) activity, which could be partially accounted for by a 10% loss of Rubisco content. Protein oxidation assay found that the Rubisco large subunit was the most prominent carbonylated protein; the level of carbonylated Rubisco large subunit increased fivefold after Cd exposure. Thiol groups in the Rubisco large subunit were oxidized, as indicated by non-reducing electrophoresis. Treating crude extract with H2O2 resulted in a similar pattern of protein oxidation and thiols oxidation with that observed in Cd-treated plants. Our study indicates that APXs in the chloroplast is a highly sensitive site of antioxidant systems under Cd stress, and the inactivation of APX could be mainly responsible for oxidative modification to Rubisco and subsequent decrease in its activity.
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Claims 12
Claim · model-written summary
Two APX isoforms, one thylakoid-bound and one stromal, were detected in tomato seedlings.
- Taxon
- tomato
Solanum lycopersicume1 - Outcome
- Two APX isoformse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“Two APX isoforms, one thylakoid-bound and one stromal, were detected”
Claim · model-written summary
Cd at 50 microM moderately increased SOD activities in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Cd at 50 microMe3
- Outcome
- SOD activitiese3
- Direction
- increasee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e3“Cd at 50 microM induced a moderate increase of SOD activities but a rapid inactivation of both APX isoenzymes”
Claim · model-written summary
Cd at 50 microM rapidly inactivated both APX isoenzymes in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Cd at 50 microMe3
- Outcome
- APX isoenzymese3
- Direction
- inactivatione3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e3“Cd at 50 microM induced a moderate increase of SOD activities but a rapid inactivation of both APX isoenzymes”
Claim · model-written summary
APX inactivation was mainly related to a decrease of ascorbate concentration in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Compound
- ascorbatee5
- Outcome
- APX inactivatione5
- Direction
- decreasee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e5“APX inactivation was mainly related to the decrease of ascorbate concentration”
Claim · model-written summary
H2O2 accumulation in chloroplast was associated with a 60% loss of Rubisco activity.
- Taxon
- tomatoSolanum lycopersicume1
- Organ / stage
- chloroplaste6
- Compound
- H2O2e6
- Outcome
- Rubisco (EC 4.1.1.39) activitye6
- Direction
- losse6
- Value
- 60%e6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e6“H2O2 accumulation in chloroplast, as a consequence of APX inactivation, was associated with a 60% loss of Rubisco (EC 4.1.1.39) activity”
Claim · model-written summary
A 10% loss of Rubisco content may partly account for the Rubisco activity loss in tomato seedlings.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e7“which could be partially accounted for by a 10% loss of Rubisco content”
Claim · model-written summary
Cd exposure increased the level of carbonylated Rubisco large subunit fivefold in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Cd exposuree2
- Gene
- Rubisco large subunite2
- Outcome
- level of carbonylated Rubisco large subunite2
- Direction
- increasede2
- Value
- fivefolde2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“the level of carbonylated Rubisco large subunit increased fivefold after Cd exposure”
Claim · model-written summary
The Rubisco large subunit was the most prominent carbonylated protein in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Gene
- Rubisco large subunite2
- Outcome
- most prominent carbonylated proteine2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“Protein oxidation assay found that the Rubisco large subunit was the most prominent carbonylated protein”
Claim · model-written summary
Thiol groups in the Rubisco large subunit were oxidized in tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Gene
- Rubisco large subunite2
- Outcome
- Thiol groupse2
- Direction
- oxidizede2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“Thiol groups in the Rubisco large subunit were oxidized”
Claim · model-written summary
Treating crude extract with H2O2 gave a protein and thiol oxidation pattern similar to that of Cd-treated tomato seedlings.
- Taxon
- tomatoSolanum lycopersicume1
- Treatment
- Treating crude extract with H2O2e2
- Outcome
- pattern of protein oxidation and thiols oxidatione2
- Direction
- similare2
- Comparator
- Cd-treated plantse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“Treating crude extract with H2O2 resulted in a similar pattern of protein oxidation and thiols oxidation with that observed in Cd-treated plants”
Claim · model-written summary
APX inactivation could be mainly responsible for oxidative modification of Rubisco and the subsequent decrease in its activity.
- Taxon
- tomatoSolanum lycopersicume1
- Gene
- APXe2
- Outcome
- oxidative modification to Rubiscoe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“the inactivation of APX could be mainly responsible for oxidative modification to Rubisco and subsequent decrease in its activity”
Claim · model-written summary
Chloroplast APXs are a highly sensitive site of the antioxidant system under Cd stress.
- Taxon
- tomatoSolanum lycopersicume1
- Organ / stage
- chloroplaste2
- Treatment
- Cd stresse2
- Gene
- APXse2
- Outcome
- highly sensitive site of antioxidant systemse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“tomato seedlings”
e2“Our study indicates that APXs in the chloroplast is a highly sensitive site of antioxidant systems under Cd stress”
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See all 13 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.