Abstract
Constitutive expression of a chimeric oat phytochrome gene in tobacco (Nicotiana tabacum) results in the accumulation of a functional 124-kilodalton photoreceptor that markedly alters the phenotype of light-grown tobacco (Keller et al. [1989] EMBO J 8: 1005-1012). Here, we provide a detailed phenotypic and biochemical characterization of homozygous tobacco expressing high levels of oat phytochrome. Phenotypic changes include a substantial inhibition of stem elongation, decreased apical dominance, increased leaf chlorophyll content, and delayed leaf senescence. Oat phytochrome synthesized in tobacco is indistinguishable from that present in etiolated oats, having photoreversible difference spectrum maxima at 665 and 730 nanometers, exhibiting negligible dark reversion of phytochrome-far red-absorbing form (Pfr) to phytochrome-red-absorbing form (Pr), and existing as a dimer with an apparent size of approximately 300 kilodaltons. Heterodimers between the oat and tobacco chromoproteins were detected. Endogenous tobacco phytochrome and transgenically expressed oat phytochrome are rapidly degraded in vivo upon photoconversion of Pr to Pfr. Breakdown of both oat and tobacco Pfr is associated with the accumulation of ubiquitin-phytochrome conjugates, suggesting that degradation occurs via the ubiquitin-dependent proteolytic pathway. This result indicates that the factors responsible for selective recognition of Pfr by the ubiquitin pathway are conserved between monocot and dicot phytochromes. More broadly, it demonstrates that the domain(s) within a plant protein responsible for its selective breakdown can be recognized by the degradation machinery of heterologous species.
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Claims 11
Claim · model-written summary
Oat phytochrome tobacco showed inhibited stem elongation.
- Taxon
- Tobacco
Nicotiana tabacumt0 - Gene
- Oat Phytochromet0
- Outcome
- stem elongatione0
- Direction
- inhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phenotypic changes include a substantial inhibition of stem elongation”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat phytochrome tobacco showed decreased apical dominance.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- Oat Phytochromet0
- Outcome
- apical dominancee0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased apical dominance”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat phytochrome tobacco showed increased leaf chlorophyll content.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- Oat Phytochromet0
- Outcome
- leaf chlorophyll contente0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased leaf chlorophyll content”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat phytochrome tobacco showed delayed leaf senescence.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- Oat Phytochromet0
- Outcome
- leaf senescencee0
- Direction
- delayede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“delayed leaf senescence”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat phytochrome synthesized in tobacco resembled the oat protein in spectrum, dark reversion and dimer size.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- Oat phytochromee0
- Outcome
- photoreversible difference spectrum maximae0
- Value
- 665 and 730 nanometerse0
- Comparator
- etiolated oatse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Oat phytochrome synthesized in tobacco is indistinguishable from that present in etiolated oats, having photoreversible difference spectrum maxima at 665 and 730 nanometers, exhibiting negligible dark reversion of phytochrome-far red-absorbing form (Pfr) to phytochrome-red-absorbing form (Pr), and existing as a dimer with an apparent size of approximately 300 kilodaltons”
Claim · model-written summary
Oat phytochrome showed negligible dark reversion in tobacco.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- Oat Phytochromet0
- Outcome
- dark reversione0
- Direction
- negligiblee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exhibiting negligible dark reversion of phytochrome-far red-absorbing form (Pfr) to phytochrome-red-absorbing form (Pr)”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat phytochrome existed as a dimer of about 300 kilodaltons in tobacco.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- Oat Phytochromet0
- Outcome
- dimere0
- Value
- approximately 300 kilodaltonse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“existing as a dimer with an apparent size of approximately 300 kilodaltons”
t0“Tobacco Expressing Functional Oat Phytochrome”
Claim · model-written summary
Oat and tobacco chromoproteins formed detectable heterodimers.
- Taxon
- tobaccoNicotiana tabacume0
- Outcome
- Heterodimers between the oat and tobacco chromoproteinse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Heterodimers between the oat and tobacco chromoproteins were detected”
Claim · model-written summary
Both endogenous tobacco and transgenic oat phytochrome degraded rapidly after Pr-to-Pfr photoconversion.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- phytochromee0
- Outcome
- degraded in vivoe0
- Direction
- rapidly degradede0
- Qualifier
- upon photoconversion of Pr to Pfre0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Endogenous tobacco phytochrome and transgenically expressed oat phytochrome are rapidly degraded in vivo upon photoconversion of Pr to Pfr”
Claim · model-written summary
Breakdown of oat and tobacco Pfr accompanied accumulation of ubiquitin-phytochrome conjugates.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- Pfre0
- Outcome
- accumulation of ubiquitin-phytochrome conjugatese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Breakdown of both oat and tobacco Pfr is associated with the accumulation of ubiquitin-phytochrome conjugates”
Claim · model-written summary
The authors infer that Pfr degradation occurs through the ubiquitin-dependent proteolytic pathway.
- Taxon
- TobaccoNicotiana tabacumt0
- Outcome
- degradatione0
- Qualifier
- ubiquitin-dependent proteolytic pathwaye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting that degradation occurs via the ubiquitin-dependent proteolytic pathway”
t0“Tobacco Expressing Functional Oat Phytochrome”