Abstract
Cysteine sulfhydryl-rich peptide thiols are believed to play important roles in the detoxification of many heavy metals and metalloids such as arsenic, mercury, and cadmium in plants. The gamma-glutamylcysteine synthetase (gamma-ECS) catalyzes the synthesis of the dipeptidethiol gamma-glu-cys (gamma-EC), the first step in the biosynthesis of phytochelatins (PCs). Arabidopsis thaliana, engineered to express the bacterial gamma-ECS gene under control of a strong constitutive actin regulatory sequence (A2), expressed gamma-ECS at levels approaching 0.1% of total protein. In response to arsenic, mercury, and cadmium stresses, the levels of gamma-EC and its derivatives, glutathione (GSH) and PCs, were increased in the A2::ECS transgenic plants to three- to 20-fold higher concentrations than the increases that occurred in wild-type (WT). Compared to cadmium and mercury treatments, arsenic treatment most significantly increased levels of gamma-EC and PCs in both the A2::ECS transgenic and WT plants. The A2::ECS transgenic plants were highly resistant to arsenic and weakly resistant to mercury. Although exposure to cadmium produced three- to fivefold increases in levels of gamma-EC-related peptides in the A2::ECS lines, these plants were significantly more sensitive to Cd(II) than WT and trace levels of Cd(II) blocked resistance to arsenic and mercury. A few possible mechanisms for gamma-ECS-enhanced arsenic and mercury resistance and cadmium hypersensitivity are discussed.
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Claims 9
Claim · model-written summary
Transgenic Arabidopsis expressed bacterial gamma-ECS at nearly 0.1% of total protein.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Gene
- gamma-ECSe0
- Outcome
- gamma-ECSe0
- Value
- 0.1% of total proteine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis thaliana, engineered to express the bacterial gamma-ECS gene under control of a strong constitutive actin regulatory sequence (A2), expressed gamma-ECS at levels approaching 0.1% of total protein.”
Claim · model-written summary
Metal-stressed A2::ECS plants had larger increases in gamma-EC, GSH and PCs than wild type.
Verbatim
e0“In response to arsenic, mercury, and cadmium stresses, the levels of gamma-EC and its derivatives, glutathione (GSH) and PCs, were increased in the A2::ECS transgenic plants to three- to 20-fold higher concentrations than the increases that occurred in wild-type (WT).”
t0“Arabidopsis plants”
Claim · model-written summary
Arsenic increased gamma-EC and PC levels most strongly among the metal treatments in transgenic and wild-type plants.
Verbatim
e0“Compared to cadmium and mercury treatments, arsenic treatment most significantly increased levels of gamma-EC and PCs in both the A2::ECS transgenic and WT plants.”
t0“Arabidopsis plants”
Claim · model-written summary
A2::ECS plants were highly resistant to arsenic.
Not reportedDirection
Verbatim
e0“The A2::ECS transgenic plants were highly resistant to arsenic and weakly resistant to mercury.”
t0“Arabidopsis plants”
Claim · model-written summary
A2::ECS plants were weakly resistant to mercury.
Not reportedDirection
Verbatim
e0“weakly resistant to mercury”
t0“Arabidopsis plants”
Claim · model-written summary
Cadmium exposure raised gamma-EC-related peptides three- to fivefold in A2::ECS lines.
- Taxon
- Arabidopsis plantst0
- Material
- A2::ECS linese0
- Treatment
- exposure to cadmiume0
- Outcome
- levels of gamma-EC-related peptidese0
- Direction
- increasese0
- Value
- three- to fivefolde0
Not reportedComparator
Verbatim
e0“exposure to cadmium produced three- to fivefold increases in levels of gamma-EC-related peptides in the A2::ECS lines”
t0“Arabidopsis plants”
Claim · model-written summary
A2::ECS plants were significantly more sensitive to cadmium than wild type.
Verbatim
e0“these plants were significantly more sensitive to Cd(II) than WT”
t0“Arabidopsis plants”
Claim · model-written summary
Trace cadmium blocked arsenic resistance in A2::ECS plants.
- Taxon
- Arabidopsis plantst0
- Treatment
- trace levels of Cd(II)e0
- Outcome
- resistance to arsenice0
- Direction
- blockede0
Not reportedComparator
Verbatim
e0“trace levels of Cd(II) blocked resistance to arsenic and mercury”
t0“Arabidopsis plants”
Claim · model-written summary
Trace cadmium blocked mercury resistance in A2::ECS plants.
- Taxon
- Arabidopsis plantst0
- Treatment
- trace levels of Cd(II)e0
- Outcome
- resistance to arsenic and mercurye0
- Direction
- blockede0
Not reportedComparator
Verbatim
e0“trace levels of Cd(II) blocked resistance to arsenic and mercury”
t0“Arabidopsis plants”
The same questions in other papers
cadmium atom · disease · ArabidopsisPositive and negative results
1 in the opposite direction
- positive
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.