Abstract
Polyamines (PAs) exert a protective effect against stress challenges, but their molecular role in this remains speculative. In order to detect the signaling role of apoplastic PA-derived hydrogen peroxide (H2O2) under abiotic stress, we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants). Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2. A-pao plants accumulated less H2O2 and exhibited less programmed cell death (PCD) than did wild-type plants, in contrast with S-pao and samdc downregulating plants. Induction of either stress-responsive genes or PCD was dependent on the level of Spd-derived apoplastic H2O2. Thus, in wild-type and A-pao plants, stress-responsive genes were efficiently induced, although in the latter at a lower rate, while S-pao plants, with higher H2O2 levels, failed to accumulate stress-responsive mRNAs, inducing PCD instead. Furthermore, decreasing intracellular PAs, while keeping normal apoplastic Spd oxidation, as in samdc downregulating transgenic plants, caused enhanced salinity-induced PCD. These results reveal that salinity induces the exodus of Spd into the apoplast, where it is catabolized by PAO, producing H2O2. The accumulated H2O2 results in the induction of either tolerance responses or PCD, depending also on the levels of intracellular PAs.
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Claims 10
Claim · model-written summary
A-pao tobacco plants accumulated less H2O2 than wild-type plants under salt stress.
- Taxon
- tobacco
Nicotiana tabacume0 - Material
- A-pao plantse1
- Treatment
- salt stresse2
- Outcome
- H2O2e1
- Direction
- lesse1
- Comparator
- wild-type plantse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e1“A-pao plants accumulated less H2O2 and exhibited less programmed cell death (PCD) than did wild-type plants, in contrast with S-pao and samdc downregulating plants”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
Claim · model-written summary
A-pao tobacco plants showed less programmed cell death than wild-type plants under salt stress.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- A-pao plantse1
- Treatment
- salt stresse2
- Outcome
- programmed cell deathe1
- Direction
- lesse1
- Comparator
- wild-type plantse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e1“A-pao plants accumulated less H2O2 and exhibited less programmed cell death (PCD) than did wild-type plants, in contrast with S-pao and samdc downregulating plants”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
Claim · model-written summary
S-pao tobacco plants had higher H2O2 levels under salt stress.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- S-pao plantse3
- Treatment
- salt stresse2
- Outcome
- H2O2 levelse3
- Direction
- highere3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
e3“S-pao plants, with higher H2O2 levels, failed to accumulate stress-responsive mRNAs, inducing PCD instead”
Claim · model-written summary
S-pao tobacco plants failed to accumulate stress-responsive mRNAs under salt stress.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- S-pao plantse3
- Treatment
- salt stresse2
- Outcome
- stress-responsive mRNAse3
- Direction
- failed to accumulatee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
e3“S-pao plants, with higher H2O2 levels, failed to accumulate stress-responsive mRNAs, inducing PCD instead”
Claim · model-written summary
Stress-responsive genes were efficiently induced in wild-type and A-pao plants, at a lower rate in A-pao plants.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- wild-type and A-pao plantse4
- Treatment
- salt stresse2
- Outcome
- stress-responsive genese4
- Direction
- efficiently inducede4
- Qualifier
- at a lower ratee4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
e4“in wild-type and A-pao plants, stress-responsive genes were efficiently induced, although in the latter at a lower rate”
Claim · model-written summary
Decreasing intracellular polyamines in samdc downregulating plants enhanced salinity-induced PCD.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- samdc downregulating transgenic plantse5
- Treatment
- decreasing intracellular PAse5
- Outcome
- salinity-induced PCDe5
- Direction
- enhancede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e5“decreasing intracellular PAs, while keeping normal apoplastic Spd oxidation, as in samdc downregulating transgenic plants, caused enhanced salinity-induced PCD”
Claim · model-written summary
Tobacco plants secreted spermidine into the apoplast under salt stress.
- Taxon
- tobaccoNicotiana tabacume0
- Treatment
- salt stresse2
- Outcome
- secreted spermidinee2
- Qualifier
- into the apoplaste2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
Claim · model-written summary
Apoplastic spermidine oxidized by the apoplastic PAO generates H2O2.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- apoplastic PAOe2
- Compound
- spermidinee2
- Outcome
- H2O2e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e2“Upon salt stress, plants secreted spermidine (Spd) into the apoplast, where it was oxidized by the apoplastic PAO, generating H2O2”
Claim · model-written summary
Induction of stress-responsive genes or PCD depended on the level of spermidine-derived apoplastic H2O2.
- Taxon
- tobaccoNicotiana tabacume0
- Compound
- Spd-derived apoplastic H2O2e6
- Outcome
- Induction of either stress-responsive genes or PCDe6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e6“Induction of either stress-responsive genes or PCD was dependent on the level of Spd-derived apoplastic H2O2”
Claim · model-written summary
Accumulated H2O2 induces tolerance responses or PCD, depending also on intracellular polyamine levels.
- Taxon
- tobaccoNicotiana tabacume0
- Compound
- H2O2e7
- Outcome
- induction of either tolerance responses or PCDe7
- Qualifier
- depending also on the levels of intracellular PAse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we developed a series of tobacco (Nicotiana tabacum cv Xanthi) transgenic plants overexpressing or downregulating apoplastic polyamine oxidase (PAO; S-pao and A-pao plants, respectively) or downregulating S-adenosyl-l-methionine decarboxylase (samdc plants)”
e7“The accumulated H2O2 results in the induction of either tolerance responses or PCD, depending also on the levels of intracellular PAs”