Abstract
Nowadays open field and protected vegetable cultivation practices require and use genotypes which are precisely tailored to their intended growth environments. Variability of this kind provides a rich source of material to uncover molecular mechanisms supporting the necessarily divergent physiological traits. In this study, typical field-optimized and glasshouse-cultivated cucumber F1 hybrids were investigated, and displayed slower growth (‘Joker’) and faster growth (‘Oitol’) in seedlings. Antioxidant capacity was lower in ‘Joker’ and higher in ‘Oitol’, pointing to a potential redox regulation of growth. The growth response of seedlings to paraquat treatment indicated stronger oxidative stress tolerance in the fast-growing ‘Oitol’. To test whether protection against nitrate-induced oxidative stress was also different, fertigation with increasing potassium nitrate content was applied. This treatment did not change growth but decreased the antioxidant capacities of both hybrids. Bioluminescence emission revealed stronger lipid peroxidation triggered by high nitrate fertigation in the leaves of ‘Joker’ seedlings. To explore the background of the more effective antioxidant protection of ‘Oitol’, levels of ascorbic acid (AsA), as well as transcriptional regulation of relevant genes of the Smirnoff–Wheeler biosynthetic pathway and ascorbate recycling, were investigated. Genes related to AsA biosynthesis were strongly upregulated at an elevated nitrate supply in ‘Oitol’ leaves only, but this was only reflected in a small increase in total AsA content. High nitrate provision also triggered expression of ascorbate–glutathion cycle genes with stronger or exclusive induction in ‘Oitol’. AsA/dehydro–ascorbate ratios were higher in ‘Oitol’ for all treatments, with a more pronounced difference at high nitrate levels. Despite strong transcriptional upregulation of ascorbate peroxidase genes (APX) in ‘Oitol’, APX activity only increased significantly in ‘Joker’. This suggests potential inhibition of APX enzyme activity specifically in ‘Oitol’ at a high nitrate supply. Our results uncover an unexpected variability in redox stress management in cucumbers, including nitrate inducibility of AsA biosynthetic and recycling pathways in certain genotypes. Possible connections between AsA biosynthesis, recycling and nitro-oxidative stress protection are discussed. Cucumber hybrids emerge as an excellent model system for studying the regulation of AsA metabolism and the roles of AsA in growth and stress tolerance.
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Claims 13
Claim · model-written summary
Joker seedlings grew more slowly than Oitol seedlings.
- Taxon
- Cucumber
Cucumis sativust0 - Material
- ‘Joker’e0
- Organ / stage
- seedlingse0
- Outcome
- slower growthe0
- Direction
- slowere0
- Comparator
- ‘Oitol’e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“displayed slower growth (‘Joker’) and faster growth (‘Oitol’) in seedlings”
t0“Cucumber”
Claim · model-written summary
Joker had lower antioxidant capacity than Oitol.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Joker’e0
- Outcome
- Antioxidant capacitye0
- Direction
- lowere0
- Comparator
- ‘Oitol’e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Antioxidant capacity was lower in ‘Joker’ and higher in ‘Oitol’”
t0“Cucumber”
Claim · model-written summary
Oitol showed stronger oxidative stress tolerance in response to paraquat.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Organ / stage
- seedlingse0
- Treatment
- paraquat treatmente0
- Outcome
- oxidative stress tolerancee0
- Direction
- strongere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The growth response of seedlings to paraquat treatment indicated stronger oxidative stress tolerance in the fast-growing ‘Oitol’”
t0“Cucumber”
Claim · model-written summary
Increasing potassium nitrate did not change seedling growth.
- Taxon
- CucumberCucumis sativust0
- Treatment
- fertigation with increasing potassium nitrate contente0
- Outcome
- growthe0
- Direction
- did not changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fertigation with increasing potassium nitrate content was applied. This treatment did not change growth”
t0“Cucumber”
Claim · model-written summary
Increasing potassium nitrate decreased antioxidant capacity in both hybrids.
- Taxon
- CucumberCucumis sativust0
- Treatment
- fertigation with increasing potassium nitrate contente0
- Outcome
- antioxidant capacitiese0
- Direction
- decreasede0
- Qualifier
- both hybridse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fertigation with increasing potassium nitrate content was applied. This treatment did not change growth but decreased the antioxidant capacities of both hybrids”
t0“Cucumber”
Claim · model-written summary
High nitrate fertigation produced stronger leaf lipid peroxidation in Joker.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Joker’e0
- Organ / stage
- leavese0
- Treatment
- high nitrate fertigatione0
- Outcome
- lipid peroxidatione0
- Direction
- strongere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stronger lipid peroxidation triggered by high nitrate fertigation in the leaves of ‘Joker’ seedlings”
t0“Cucumber”
Claim · model-written summary
Elevated nitrate strongly upregulated ascorbic acid biosynthesis genes only in Oitol leaves.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Organ / stage
- leavese0
- Treatment
- elevated nitrate supplye0
- Gene
- Genes related to AsA biosynthesise0
- Outcome
- Genes related to AsA biosynthesise0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Genes related to AsA biosynthesis were strongly upregulated at an elevated nitrate supply in ‘Oitol’ leaves only”
t0“Cucumber”
Claim · model-written summary
Oitol showed only a small increase in total AsA under elevated nitrate.
- Taxon
- CucumberCucumis sativust0
- Outcome
- total AsA contente0
- Direction
- increasee0
- Qualifier
- smalle0
Not reportedMaterialTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“small increase in total AsA content”
t0“Cucumber”
Claim · model-written summary
High nitrate induced ascorbate–glutathion cycle genes more strongly or exclusively in Oitol.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Treatment
- High nitrate provisione0
- Gene
- ascorbate–glutathion cycle genese0
- Outcome
- expression of ascorbate–glutathion cycle genese0
- Direction
- stronger or exclusive inductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High nitrate provision also triggered expression of ascorbate–glutathion cycle genes with stronger or exclusive induction in ‘Oitol’”
t0“Cucumber”
Claim · model-written summary
AsA/dehydro–ascorbate ratios were higher in Oitol under all treatments, especially high nitrate.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Outcome
- AsA/dehydro–ascorbate ratiose0
- Direction
- highere0
- Qualifier
- for all treatments, with a more pronounced difference at high nitrate levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AsA/dehydro–ascorbate ratios were higher in ‘Oitol’ for all treatments, with a more pronounced difference at high nitrate levels”
t0“Cucumber”
Claim · model-written summary
APX genes were strongly upregulated in Oitol.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Gene
- ascorbate peroxidase genes (APX)e0
- Outcome
- transcriptional upregulatione0
- Direction
- upregulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“strong transcriptional upregulation of ascorbate peroxidase genes (APX) in ‘Oitol’”
t0“Cucumber”
Claim · model-written summary
APX activity increased significantly only in Joker.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“APX activity only increased significantly in ‘Joker’”
t0“Cucumber”
Claim · model-written summary
The authors suggest potential inhibition of APX activity in Oitol under high nitrate.
- Taxon
- CucumberCucumis sativust0
- Material
- ‘Oitol’e0
- Gene
- APXe0
- Outcome
- APX enzyme activitye0
- Direction
- inhibitione0
- Qualifier
- at a high nitrate supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“potential inhibition of APX enzyme activity specifically in ‘Oitol’ at a high nitrate supply”
t0“Cucumber”
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