Abstract
The production of superoxide radical (O2−) was studied in plasma membrane vesicles isolated by aqueous polymer two-phase partitioning from roots of zinc-sufficient and zinc-deficient bean (Phaseolus vulgaris L. cv. Prélude) plants. The two populations of vesicles were highly enriched in plasma membrane and had similar composition as evidenced by the specific membrane marker enzymes. Vesicles from zinc-deficient roots showed higher rates of NAD(P)H oxidation compared to vesicles from zinc-sufficient plants. The NAD(P)H-dependent formation of O2− in plasma membrane vesicles was also highly increased by zinc deficiency. For both activities, a higher response to zinc deficiency was observed when NADPH was used as electron source. Re-supply of zinc to deficient plants for 24 h substantially decreased the rates of NAD(P)H oxidation and 02− production in isolated vesicles. The NADPH-dependent O2− generation was strongly stimulated by FAD and showed a high pH optimum; it was scarcely affected by Triton X-100 or even inhibited in the presence of FAD and was almost insensitive to Antimycin A. The results suggest the presence at the plasma membrane of bean roots of an O2− generating activity, preferentially utilizing NADPH, which is affected by the zinc nutritional status of the plant. This finding, together with previous observations on cytosolic and microsomal fractions prepared from zinc-deficient roots of different plants, is consistent with a role of zinc in membrane stabilization by controlling the level of oxidizing O2 species.
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Claims 9
Claim · model-written summary
Vesicles from zinc-deficient roots had higher NAD(P)H oxidation rates than zinc-sufficient plants.
Verbatim
t0“bean plants”
e0“Vesicles from zinc-deficient roots showed higher rates of NAD(P)H oxidation compared to vesicles from zinc-sufficient plants.”
Claim · model-written summary
Zinc deficiency increased superoxide formation in plasma membrane vesicles.
- Taxon
- bean plantst0
- Treatment
- zinc deficiencye0
- Outcome
- NAD(P)H-dependent formation of O2−e0
- Direction
- increasede0
Not reportedComparator
Verbatim
t0“bean plants”
e0“The NAD(P)H-dependent formation of O2− in plasma membrane vesicles was also highly increased by zinc deficiency.”
Claim · model-written summary
Both activities responded more strongly to zinc deficiency with NADPH as the electron source.
Verbatim
t0“bean plants”
e0“For both activities, a higher response to zinc deficiency was observed when NADPH was used as electron source.”
Claim · model-written summary
Zinc resupply for 24 hours decreased NAD(P)H oxidation rates.
- Taxon
- bean plantst0
- Treatment
- Re-supply of zinc to deficient plants for 24 he0
- Outcome
- rates of NAD(P)H oxidatione0
- Direction
- decreasede0
Not reportedComparator
Verbatim
t0“bean plants”
e0“Re-supply of zinc to deficient plants for 24 h substantially decreased the rates of NAD(P)H oxidation and 02− production in isolated vesicles.”
Claim · model-written summary
Zinc resupply for 24 hours decreased superoxide production.
- Taxon
- bean plantst0
- Treatment
- Re-supply of zinc to deficient plants for 24 he0
- Outcome
- 02− productione0
- Direction
- decreasede0
Not reportedComparator
Verbatim
t0“bean plants”
e0“Re-supply of zinc to deficient plants for 24 h substantially decreased the rates of NAD(P)H oxidation and 02− production in isolated vesicles.”
Claim · model-written summary
FAD strongly stimulated NADPH-dependent superoxide generation.
- Taxon
- bean plantst0
- Treatment
- FADe0
- Outcome
- NADPH-dependent O2− generatione0
- Direction
- strongly stimulatede0
Not reportedComparator
Verbatim
t0“bean plants”
e0“The NADPH-dependent O2− generation was strongly stimulated by FAD”
Claim · model-written summary
NADPH-dependent superoxide generation had a high pH optimum.
Verbatim
t0“bean plants”
e0“The NADPH-dependent O2− generation was strongly stimulated by FAD and showed a high pH optimum”
Claim · model-written summary
Triton X-100 scarcely affected NADPH-dependent superoxide generation and inhibited it with FAD.
- Taxon
- bean plantst0
- Treatment
- Triton X-100e0
- Outcome
- scarcely affectede0
- Direction
- scarcely affectede0
- Qualifier
- in the presence of FADe0
Not reportedComparator
Verbatim
t0“bean plants”
e0“it was scarcely affected by Triton X-100 or even inhibited in the presence of FAD”
Claim · model-written summary
Antimycin A had almost no effect on NADPH-dependent superoxide generation.
Not reportedComparator
Verbatim
t0“bean plants”
e0“was almost insensitive to Antimycin A”
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