Abstract
Blue-light-dependent photomorphogenesis in Arabidopsis is regulated principally by the cryptochrome flavin-type photoreceptors, which control hypocotyl growth inhibition, cotyledon and leaf expansion, and the expression of light-regulated genes. Interestingly the plant hormone cytokinin induces similar responses when added exogenously to germinating seedlings, suggesting a link between cryptochrome and cytokinin signalling pathways. In this work we explore the relationship between cryptochrome and cytokinin signalling pathways in the promotion of photomorphogenesis. The effect of exogenously added cytokinins on hypocotyl growth inhibition occurs in the dark, and is largely independent and additive to that of cryptochromes in blue light, via distinct signalling pathways. By contrast, cytokinin-dependent stimulation of anthocyanin accumulation occurs only in light, and interacts with the signalling pathway downstream of cryptochrome 1 (CRY1) at the level of transcript accumulation of anthocyanin biosynthetic genes. Mutants in elongated hypocotyl 5 (hy5), a downstream intermediate in the CRY1 signalling pathway, show a reduced induction of anthocyanin accumulation in blue light by cytokinins, similar to that observed for cryptochrome (cry1) mutants. Furthermore cytokinins are shown to increase levels of HY5 protein accumulation, suggesting that cytokinins may function by reducing HY5 degradation by COP1 (constitutively photomorphogenic 1). As both cryptochrome and cytokinin signalling pathways increase HY5 protein levels, and as HY5 binds to the promoters of anthocyanin biosynthetic enzymes to stimulate gene expression, it is concluded that the regulation of HY5 protein stability represents a point of convergence between cryptochrome and cytokinin signalling pathways.
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Claims 5
Claim · model-written summary
Exogenous cytokinin inhibited hypocotyl growth in darkness through a pathway largely independent of and additive to cryptochrome signalling.
- Taxon
- Arabidopsis
Arabidopsist0 - Treatment
- exogenously added cytokininse0
- Outcome
- hypocotyl growth inhibitione0
- Direction
- inhibitione0
- Qualifier
- in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of exogenously added cytokinins on hypocotyl growth inhibition occurs in the dark, and is largely independent and additive to that of cryptochromes in blue light, via distinct signalling pathways”
t0“HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana”
Claim · model-written summary
Cytokinin stimulated anthocyanin accumulation only in light and interacted with signalling downstream of CRY1.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- cryptochrome 1 (CRY1)e0
- Outcome
- anthocyanin accumulatione0
- Direction
- stimulatione0
- Qualifier
- only in lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin-dependent stimulation of anthocyanin accumulation occurs only in light, and interacts with the signalling pathway downstream of cryptochrome 1 (CRY1) at the level of transcript accumulation of anthocyanin biosynthetic genes”
t0“HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana”
Claim · model-written summary
Hy5 and cry1 mutants had reduced cytokinin induction of anthocyanin accumulation in blue light.
- Taxon
- ArabidopsisArabidopsist0
- Material
- hy5e0
- Treatment
- cytokininse0
- Gene
- CRY1e0
- Outcome
- anthocyanin accumulatione0
- Direction
- reduced inductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mutants in elongated hypocotyl 5 (hy5), a downstream intermediate in the CRY1 signalling pathway, show a reduced induction of anthocyanin accumulation in blue light by cytokinins, similar to that observed for cryptochrome (cry1) mutants”
t0“HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana”
Claim · model-written summary
Cytokinins increased HY5 protein accumulation.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- cytokininse0
- Gene
- HY5e0
- Outcome
- HY5 protein accumulatione0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinins are shown to increase levels of HY5 protein accumulation”
t0“HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana”
Claim · model-written summary
The authors concluded that HY5 protein stability is a convergence point between cryptochrome and cytokinin signalling.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- HY5e0
- Outcome
- HY5 protein stabilitye0
- Qualifier
- point of convergencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the regulation of HY5 protein stability represents a point of convergence between cryptochrome and cytokinin signalling pathways”
t0“HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana”
The same questions in other papers
class · molecular: expression · ArabidopsisPositive and negative results
45 papers in the same direction as this paper · 28 in the opposite direction · 1 reporting no difference from an alternative
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