Abstract
Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei were investigated by Feulgen cytophotometry, thermal denaturation, renaturation, and DNA‐DNA hybridization studies during sequential leaf senescence. Cytophotometric Feulgen‐DNA comparison measurements between young and senescing nuclei displayed 18% reduction in Feulgen‐DNA values, with a corresponding decrease in nuclear area in senescing nuclei. Hydrolysis kinetics indicated that the loss was not due to compactness of the DNA as the curves for older nuclei were consistently lower than curves generated from younger nuclei. DNA loss in senescing nuclei was associated with a decrease in euchromatin or shift from euchromatin to facultative heterochromatin. Purified DNA from young and senescing leaf nuclei did not display different thermal profiles nor did hydroxylapatite chromatography reassociation curves. DNA‐DNA hybridization in free solution from young and senescing leaf DNA performed by a Gilford thermo‐programmer system indicated that DNA of senescing tobacco nuclei reassociated more slowly than DNA from young nuclei and the mixture of young and senescing leaf DNA displayed intermediate reassociation values. The study indicates that the DNA changes during senescence involve a complex phenomenon which includes the possibility of small single strand nicks undetectable by thermal denaturation, and a loss of small double strand fragments which were detectable only by precise DNA‐DNA free solution reassociation and not by hydroxylapatite chromatography reassociation.
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Claims 10
Claim · model-written summary
Senescing tobacco leaf nuclei showed an 18% reduction in Feulgen-DNA values relative to young nuclei.
- Taxon
- tobacco (Nicotiana tabacum)
Nicotiana tabacume0 - Organ / stage
- senescing nucleie1
- Outcome
- Feulgen‐DNA valuese1
- Direction
- reductione1
- Value
- 18%e1
- Comparator
- younge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e1“Cytophotometric Feulgen‐DNA comparison measurements between young and senescing nuclei displayed 18% reduction in Feulgen‐DNA values, with a corresponding decrease in nuclear area in senescing nuclei”
Claim · model-written summary
Senescing tobacco leaf nuclei showed a decrease in nuclear area relative to young nuclei.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Organ / stage
- senescing nucleie1
- Outcome
- nuclear areae1
- Direction
- decreasee1
- Comparator
- younge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e1“Cytophotometric Feulgen‐DNA comparison measurements between young and senescing nuclei displayed 18% reduction in Feulgen‐DNA values, with a corresponding decrease in nuclear area in senescing nuclei”
Claim · model-written summary
Hydrolysis kinetics indicated that the DNA loss in senescing nuclei was not due to DNA compactness, since hydrolysis curves for older nuclei were consistently lower than for younger nuclei.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Outcome
- curves for older nucleie2
- Direction
- lowere2
- Qualifier
- the loss was not due to compactness of the DNAe2
- Comparator
- younger nucleie2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e2“Hydrolysis kinetics indicated that the loss was not due to compactness of the DNA as the curves for older nuclei were consistently lower than curves generated from younger nuclei”
Claim · model-written summary
DNA loss in senescing nuclei was associated with a decrease in euchromatin, or a shift from euchromatin to facultative heterochromatin.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Organ / stage
- senescing nucleie3
- Outcome
- euchromatine3
- Direction
- decreasee3
- Qualifier
- shift from euchromatin to facultative heterochromatine3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e3“DNA loss in senescing nuclei was associated with a decrease in euchromatin or shift from euchromatin to facultative heterochromatin”
Claim · model-written summary
Purified DNA from young and senescing leaf nuclei showed no difference in thermal profiles.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Organ / stage
- leaf nucleie4
- Outcome
- thermal profilese4
- Direction
- no_changeinferrede4
- Comparator
- younge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e4“Purified DNA from young and senescing leaf nuclei did not display different thermal profiles nor did hydroxylapatite chromatography reassociation curves”
Claim · model-written summary
Purified DNA from young and senescing leaf nuclei showed no difference in hydroxylapatite chromatography reassociation curves.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Organ / stage
- leaf nucleie4
- Outcome
- hydroxylapatite chromatography reassociation curvese4
- Direction
- no_changeinferrede4
- Comparator
- younge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e4“Purified DNA from young and senescing leaf nuclei did not display different thermal profiles nor did hydroxylapatite chromatography reassociation curves”
Claim · model-written summary
DNA of senescing tobacco nuclei reassociated more slowly in free solution than DNA from young nuclei.
- Taxon
- tobaccoNicotiana tabacume5
- Outcome
- reassociatione5
- Direction
- more slowlye5
- Comparator
- young nucleie5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“DNA of senescing tobacco nuclei reassociated more slowly than DNA from young nuclei and the mixture of young and senescing leaf DNA displayed intermediate reassociation values”
Claim · model-written summary
The mixture of young and senescing leaf DNA displayed intermediate reassociation values.
- Taxon
- tobaccoNicotiana tabacume5
- Outcome
- reassociation valuese5
- Direction
- intermediatee5
- Qualifier
- the mixture of young and senescing leaf DNAe5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“DNA of senescing tobacco nuclei reassociated more slowly than DNA from young nuclei and the mixture of young and senescing leaf DNA displayed intermediate reassociation values”
Claim · model-written summary
Small single-strand nicks undetectable by thermal denaturation may contribute to DNA changes during senescence.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Outcome
- DNA changes during senescencee6
- Qualifier
- small single strand nicks undetectable by thermal denaturatione6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e6“The study indicates that the DNA changes during senescence involve a complex phenomenon which includes the possibility of small single strand nicks undetectable by thermal denaturation, and a loss of small double strand fragments which were detectable only by precise DNA‐DNA free solution reassociation and not by hydroxylapatite chromatography reassociation”
Claim · model-written summary
A loss of small double-strand fragments may contribute to DNA changes during senescence.
- Taxon
- tobacco (Nicotiana tabacum)Nicotiana tabacume0
- Outcome
- DNA changes during senescencee6
- Qualifier
- a loss of small double strand fragmentse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei”
e6“The study indicates that the DNA changes during senescence involve a complex phenomenon which includes the possibility of small single strand nicks undetectable by thermal denaturation, and a loss of small double strand fragments which were detectable only by precise DNA‐DNA free solution reassociation and not by hydroxylapatite chromatography reassociation”