Abstract
Chilling adversely affects the photosynthesis of thermophilic plants, which further leads to a decline in growth and yield. The role of melatonin (MT) in the stress response of plants has been investigated, while the mechanisms by which MT regulates the chilling tolerance of chilling-sensitive cucumber remain unclear. This study demonstrated that MT positively regulated the chilling tolerance of cucumber seedlings and that 1.0 μmol⋅L –1 was the optimum concentration, of which the chilling injury index, electrolyte leakage (EL), and malondialdehyde (MDA) were the lowest, while growth was the highest among all treatments. MT triggered the activity and expression of antioxidant enzymes, which in turn decreased hydrogen peroxide (H 2 O 2 ) and superoxide anion (O 2 ⋅– ) accumulation caused by chilling stress. Meanwhile, MT attenuated the chilling-induced decrease, in the net photosynthetic rate (Pn) and promoted photoprotection for both photosystem II (PSII) and photosystem I (PSI), regarding the higher maximum quantum efficiency of PSII (Fv/Fm), actual photochemical efficiency (ΦPS II ), the content of active P700 (ΔI/I 0 ), and photosynthetic electron transport. The proteome analysis and western blot data revealed that MT upregulated the protein levels of PSI reaction center subunits (PsaD, PsaE, PsaF, PsaH, and PsaN), PSII-associated protein PsbA (D1), and ribulose-1,5-bisphosphate carboxylase or oxygenase large subunit (RBCL) and Rubisco activase (RCA). These results suggest that MT enhances the chilling tolerance of cucumber through the activation of antioxidant enzymes and the induction of key PSI-, PSII-related and carbon assimilation genes, which finally alleviates damage to the photosynthetic apparatus and decreases oxidative damage to cucumber seedlings under chilling stress.
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Claims 9
Claim · model-written summary
Melatonin improved chilling tolerance; 1.0 μmol⋅L –1 was optimal.
- Taxon
- cucumber seedlings
Cucumis sativuse0 - Treatment
- MTe0
- Outcome
- chilling tolerancee0
- Direction
- positivelye0
- Value
- 1.0 μmol⋅L –1e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“MT positively regulated the chilling tolerance of cucumber seedlings and that 1.0 μmol⋅L –1 was the optimum concentration”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
At the optimal melatonin concentration, chilling injury index, electrolyte leakage, and malondialdehyde were lowest.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe2
- Outcome
- chilling injury index, electrolyte leakage (EL), and malondialdehyde (MDA)e0
- Direction
- loweste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chilling injury index, electrolyte leakage (EL), and malondialdehyde (MDA) were the lowest”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin gave the highest growth among treatments.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe2
- Outcome
- growthe0
- Direction
- higheste0
- Comparator
- all treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth was the highest among all treatments”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin increased antioxidant enzyme activity and expression.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe0
- Outcome
- activity and expression of antioxidant enzymese0
- Direction
- triggerede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“MT triggered the activity and expression of antioxidant enzymes”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin reduced chilling-induced hydrogen peroxide and superoxide accumulation.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe2
- Outcome
- hydrogen peroxide (H 2 O 2 ) and superoxide anion (O 2 ⋅– ) accumulatione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased hydrogen peroxide (H 2 O 2 ) and superoxide anion (O 2 ⋅– ) accumulation caused by chilling stress”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin attenuated the chilling-induced fall in net photosynthetic rate.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe0
- Outcome
- net photosynthetic rate (Pn)e0
- Direction
- attenuatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“MT attenuated the chilling-induced decrease, in the net photosynthetic rate (Pn)”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin improved PSII and PSI photoprotection metrics and electron transport.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe2
- Outcome
- maximum quantum efficiency of PSII (Fv/Fm), actual photochemical efficiency (ΦPS II ), the content of active P700 (ΔI/I 0 ), and photosynthetic electron transporte0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher maximum quantum efficiency of PSII (Fv/Fm), actual photochemical efficiency (ΦPS II ), the content of active P700 (ΔI/I 0 ), and photosynthetic electron transport”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin upregulated PSI reaction-center subunit proteins.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe0
- Gene
- PsaD, PsaE, PsaF, PsaH, and PsaNe0
- Outcome
- protein levels of PSI reaction center subunitse0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“MT upregulated the protein levels of PSI reaction center subunits (PsaD, PsaE, PsaF, PsaH, and PsaN)”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
Claim · model-written summary
Melatonin upregulated PsbA, RBCL and RCA protein levels.
- Taxon
- cucumber seedlingsCucumis sativuse1
- Treatment
- MTe2
- Gene
- PsbA (D1)e0
- Outcome
- protein levelse2
- Direction
- upregulatede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PSII-associated protein PsbA (D1), and ribulose-1,5-bisphosphate carboxylase or oxygenase large subunit (RBCL) and Rubisco activase (RCA)”
t0“Melatonin Promotes the Chilling Tolerance of Cucumber Seedlings by Regulating Antioxidant System and Relieving Photoinhibition”
e1“chilling tolerance of cucumber seedlings”
e2“MT upregulated the protein levels”
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