Abstract
Cytokinins (CKs) are involved in the regulation of plant development including plastid differentiation and function. Partial location of CK biosynthetic pathways in plastids suggests the importance of CKs for chloroplast development. The impact of genetically modified CK metabolism on endogenous CK, indole-3-acetic acid, and abscisic acid contents in leaves and isolated intact chloroplasts of Nicotiana tabacum was determined by liquid chromatography/mass spectrometry and two-dimensional high-performance liquid chromatography, and alterations in chloroplast ultrastructure by electron microscopy. Ectopic expression of Sho, a gene encoding a Petunia hybrida isopentenyltransferase, was employed to raise CK levels. The increase in CK levels was lower in chloroplasts than in leaves. CK levels were reduced in leaves of tobacco harbouring a CK oxidase/dehydrogenase gene, AtCKX3. The total CK content also decreased in chloroplasts, but CK phosphate levels were higher than in the wild type. In a transformant overexpressing a maize beta-glucosidase gene, Zm-p60.1, naturally targeted to plastids, a decrease of CK-O-glucosides in chloroplasts was found. In leaves, the changes were not significant. CK-O-glucosides accumulated to very high levels in leaves, but not in chloroplasts, of plants overexpressing a ZOG1 gene, encoding trans-zeatin-O-glucosyltransferase from Phaseolus lunatus. Manipulation of the CK content affected levels of indole-3-acetic and abscisic acid. Chloroplasts of plants constitutively overexpressing Sho displayed ultrastructural alterations including the occasional occurrence of crystalloids and an increased number of plastoglobuli. The other transformants did not exhibit any major differences in chloroplast ultrastructure. The results suggest that plant hormone compartmentation plays an important role in hormone homeostasis and that chloroplasts are rather independent organelles with respect to regulation of CK metabolism.
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Claims 12
Claim · model-written summary
Sho expression raised CK levels less in chloroplasts than leaves.
- Taxon
- tobacco
Nicotiana tabacumt0 - Organ / stage
- chloroplastse0
- Treatment
- Ectopic expression of Shoe0
- Gene
- Shoe0
- Outcome
- CK levelse0
- Direction
- lowere0
- Comparator
- leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ectopic expression of Sho, a gene encoding a Petunia hybrida isopentenyltransferase, was employed to raise CK levels. The increase in CK levels was lower in chloroplasts than in leaves”
t0“transgenic tobacco”
Claim · model-written summary
AtCKX3 reduced CK levels in tobacco leaves.
- Taxon
- tobaccoNicotiana tabacume0
- Organ / stage
- leavese0
- Treatment
- harbouring a CK oxidase/dehydrogenase gene, AtCKX3e0
- Gene
- AtCKX3e0
- Outcome
- CK levelse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CK levels were reduced in leaves of tobacco harbouring a CK oxidase/dehydrogenase gene, AtCKX3”
Claim · model-written summary
Total CK content decreased in chloroplasts of AtCKX3 tobacco.
- Taxon
- tobaccoNicotiana tabacume0
- Organ / stage
- chloroplastse0
- Treatment
- harbouring a CK oxidase/dehydrogenase gene, AtCKX3e0
- Gene
- AtCKX3e0
- Outcome
- total CK contente0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CK levels were reduced in leaves of tobacco harbouring a CK oxidase/dehydrogenase gene, AtCKX3. The total CK content also decreased in chloroplasts”
Claim · model-written summary
CK phosphate levels were higher than wild type in AtCKX3 tobacco chloroplasts.
- Taxon
- tobaccoNicotiana tabacume0
- Organ / stage
- chloroplastse0
- Treatment
- harbouring a CK oxidase/dehydrogenase gene, AtCKX3e0
- Gene
- AtCKX3e0
- Outcome
- CK phosphate levelse0
- Direction
- highere0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tobacco harbouring a CK oxidase/dehydrogenase gene, AtCKX3. The total CK content also decreased in chloroplasts, but CK phosphate levels were higher than in the wild type”
Claim · model-written summary
Zm-p60.1 overexpression decreased chloroplast CK-O-glucosides.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- chloroplastse0
- Treatment
- overexpressing a maize beta-glucosidase gene, Zm-p60.1e0
- Gene
- Zm-p60.1e0
- Outcome
- CK-O-glucosidese0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In a transformant overexpressing a maize beta-glucosidase gene, Zm-p60.1, naturally targeted to plastids, a decrease of CK-O-glucosides in chloroplasts was found”
t0“transgenic tobacco”
Claim · model-written summary
Zm-p60.1 overexpression did not significantly alter CK-O-glucosides in leaves.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leavese0
- Treatment
- overexpressing a maize beta-glucosidase gene, Zm-p60.1e1
- Gene
- Zm-p60.1e1
- Outcome
- CK-O-glucosidese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a decrease of CK-O-glucosides in chloroplasts was found. In leaves, the changes were not significant”
t0“transgenic tobacco”
e1“In a transformant overexpressing a maize beta-glucosidase gene, Zm-p60.1, naturally targeted to plastids, a decrease of CK-O-glucosides in chloroplasts was found”
Claim · model-written summary
ZOG1 overexpression accumulated CK-O-glucosides to very high levels in leaves but not chloroplasts.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leavese0
- Treatment
- overexpressing a ZOG1 genee0
- Gene
- ZOG1e0
- Outcome
- CK-O-glucosidese0
- Direction
- very high levelse0
- Qualifier
- but not in chloroplastse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CK-O-glucosides accumulated to very high levels in leaves, but not in chloroplasts, of plants overexpressing a ZOG1 gene”
t0“transgenic tobacco”
Claim · model-written summary
CK manipulation affected indole-3-acetic and abscisic acid levels.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- Manipulation of the CK contente0
- Outcome
- levels of indole-3-acetic and abscisic acide0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Manipulation of the CK content affected levels of indole-3-acetic and abscisic acid”
t0“transgenic tobacco”
Claim · model-written summary
Sho overexpression caused chloroplast crystalloids and more plastoglobuli.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Chloroplastse0
- Treatment
- constitutively overexpressing Shoe0
- Gene
- Shoe0
- Outcome
- ultrastructural alterations including the occasional occurrence of crystalloids and an increased number of plastoglobulie0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chloroplasts of plants constitutively overexpressing Sho displayed ultrastructural alterations including the occasional occurrence of crystalloids and an increased number of plastoglobuli”
t0“transgenic tobacco”
Claim · model-written summary
Other transformants had no major chloroplast ultrastructural differences.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- chloroplast ultrastructuree0
- Direction
- did not exhibit any major differencese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The other transformants did not exhibit any major differences in chloroplast ultrastructure”
t0“transgenic tobacco”
Claim · model-written summary
Hormone compartmentation appears important for hormone homeostasis.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- hormone homeostasise0
- Qualifier
- plant hormone compartmentatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plant hormone compartmentation plays an important role in hormone homeostasis”
t0“transgenic tobacco”
Claim · model-written summary
Chloroplasts appear relatively independent in CK metabolism regulation.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- chloroplastse0
- Outcome
- regulation of CK metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chloroplasts are rather independent organelles with respect to regulation of CK metabolism”
t0“transgenic tobacco”