Abstract
PHYTOCHROME-INTERACTING FACTOR5 (PIF5), a basic helix-loop-helix transcription factor, interacts specifically with the photoactivated form of phytochrome B (phyB). Here, we report that dark-grown Arabidopsis thaliana seedlings overexpressing PIF5 (PIF5-OX) exhibit exaggerated apical hooks and short hypocotyls, reminiscent of the triple response induced by elevated ethylene levels, whereas pif5 mutants fail to maintain tight hooks like those of wild-type seedlings. Silver ions, an ethylene receptor blocker, rescued the triple-response phenotype, and we show that PIF5-OX seedlings express enhanced levels of key ethylene biosynthesis enzymes and produce elevated ethylene levels. Exposure of PIF5-OX seedlings to prolonged continuous red light (Rc) promotes hypocotyl elongation relative to dark controls, the reciprocal of the Rc-imposed hypocotyl inhibition displayed by wild-type seedlings. In contrast with this PIF5-OX hyposensitivity to Rc, pif5 mutant seedlings are hypersensitive relative to wild-type seedlings. We show that this contrast is due to reciprocal changes in phyB protein levels in prolonged Rc. Compared with wild-type seedlings, PIF5-OX seedlings have reduced, whereas pif5 mutants have increased, phyB (and phyC) levels in Rc. The phyB degradation in the overexpressors depends on a functional phyB binding motif in PIF5 and involves the 26S proteasome pathway. Our data thus indicate that overexpressed PIF5 causes altered ethylene levels, which promote the triple response in darkness, whereas in the light, the interaction of photoactivated phyB with PIF5 causes degradation of the photoreceptor protein. The evidence suggests that endogenous PIF5 negatively regulates phyB-imposed hypocotyl inhibition in prolonged Rc by reducing photoreceptor abundance, and thereby photosensory capacity, rather than functioning as a signaling intermediate.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 12
Claim · model-written summary
Dark-grown PIF5-OX seedlings had exaggerated apical hooks.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Material
- PIF5-OXe0
- Gene
- PIF5e0
- Outcome
- exaggerated apical hookse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark-grown Arabidopsis thaliana seedlings overexpressing PIF5 (PIF5-OX) exhibit exaggerated apical hooks and short hypocotyls”
Claim · model-written summary
Dark-grown PIF5-OX seedlings had short hypocotyls.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- PIF5-OXe0
- Gene
- PIF5e0
- Outcome
- short hypocotylse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark-grown Arabidopsis thaliana seedlings overexpressing PIF5 (PIF5-OX) exhibit exaggerated apical hooks and short hypocotyls”
Claim · model-written summary
pif5 mutants failed to maintain tight hooks like wild-type seedlings.
Not reportedTaxon
Verbatim
e0“pif5 mutants fail to maintain tight hooks like those of wild-type seedlings.”
Claim · model-written summary
Silver ions rescued the triple-response phenotype.
Not reportedTaxonComparator
Verbatim
e0“Silver ions, an ethylene receptor blocker, rescued the triple-response phenotype”
Claim · model-written summary
PIF5-OX seedlings had enhanced levels of ethylene biosynthesis enzymes.
Not reportedTaxon
Verbatim
e0“PIF5-OX seedlings express enhanced levels of key ethylene biosynthesis enzymes and produce elevated ethylene levels.”
Claim · model-written summary
PIF5-OX seedlings produced elevated ethylene levels.
Not reportedTaxon
Verbatim
e0“PIF5-OX seedlings express enhanced levels of key ethylene biosynthesis enzymes and produce elevated ethylene levels.”
Claim · model-written summary
Prolonged red light promoted hypocotyl elongation in PIF5-OX seedlings relative to dark controls.
- Material
- PIF5-OXe0
- Treatment
- prolonged continuous red light (Rc)e0
- Outcome
- hypocotyl elongatione0
- Direction
- promotese0
- Comparator
- dark controlse0
Not reportedTaxon
Verbatim
e0“Exposure of PIF5-OX seedlings to prolonged continuous red light (Rc) promotes hypocotyl elongation relative to dark controls”
Claim · model-written summary
Red light inhibited wild-type hypocotyls.
Not reportedTaxonComparatorDirection
Verbatim
e0“Rc-imposed hypocotyl inhibition displayed by wild-type seedlings”
Claim · model-written summary
pif5 mutant seedlings were hypersensitive to red light relative to wild type.
Not reportedTaxon
Verbatim
e0“pif5 mutant seedlings are hypersensitive relative to wild-type seedlings.”
Claim · model-written summary
PIF5-OX seedlings had reduced phyB and phyC levels under red light.
Not reportedTaxon
Verbatim
e0“PIF5-OX seedlings have reduced, whereas pif5 mutants have increased, phyB (and phyC) levels in Rc.”
Claim · model-written summary
pif5 mutants had increased phyB and phyC levels under red light.
Not reportedTaxon
Verbatim
e0“PIF5-OX seedlings have reduced, whereas pif5 mutants have increased, phyB (and phyC) levels in Rc.”
Claim · model-written summary
phyB degradation in PIF5 overexpressors depended on a functional PIF5 binding motif and involved the 26S proteasome.
Not reportedTaxon
Verbatim
e0“The phyB degradation in the overexpressors depends on a functional phyB binding motif in PIF5 and involves the 26S proteasome pathway.”
The same questions in other papers
light · growth · Arabidopsis thaliana (thale cress)Results differ
29 papers in the same direction as this paper · 14 in the opposite direction
- negative
- negative
- negative
40 papers more in this group
See all 44 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.