Abstract
One of the classical functions of the plant hormone cytokinin is the regulation of plastid development, but the underlying molecular mechanisms remain elusive. In this study, we employed a genetic approach to evaluate the role of cytokinin and its signaling pathway in the light-induced development of chloroplasts from etioplasts in Arabidopsis (Arabidopsis thaliana). Cytokinin increases the rate of greening and stimulates ultrastructural changes characteristic for the etioplast-to-chloroplast transition. The steady-state levels of metabolites of the tetrapyrrole biosynthesis pathway leading to the production of chlorophyll are enhanced by cytokinin. This effect of cytokinin on metabolite levels arises due to the modulation of expression for chlorophyll biosynthesis genes such as HEMA1, GUN4, GUN5, and CHLM Increased expression of HEMA1 is reflected in an enhanced level of the encoded glutamyl-tRNA reductase, which catalyzes one of the rate-limiting steps of chlorophyll biosynthesis. Mutant analysis indicates that the cytokinin receptors ARABIDOPSIS HIS KINASE2 (AHK2) and AHK3 play a central role in this process. Furthermore, the B-type ARABIDOPSIS RESPONSE REGULATOR1 (ARR1), ARR10, and ARR12 play an important role in mediating the transcriptional output during etioplast-chloroplast transition. B-type ARRs bind to the promotors of HEMA1 and LHCB6 genes, indicating that cytokinin-dependent transcription factors directly regulate genes of chlorophyll biosynthesis and the light harvesting complex. Together, these results demonstrate an important role for the cytokinin signaling pathway in chloroplast development, with the direct transcriptional regulation of chlorophyll biosynthesis genes as a key aspect for this hormonal control.
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Claims 9
Claim · model-written summary
Cytokinin increased greening rate.
- Taxon
- Arabidopsis (Arabidopsis thaliana)
Arabidopsis thalianae1 - Treatment
- Cytokinine0
- Outcome
- rate of greeninge0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cytokinin increases the rate of greening”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Cytokinin stimulated ultrastructural etioplast-to-chloroplast changes.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Treatment
- Cytokinine2
- Outcome
- ultrastructural changes characteristic for the etioplast-to-chloroplast transitione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stimulates ultrastructural changes characteristic for the etioplast-to-chloroplast transition”
e1“Arabidopsis (Arabidopsis thaliana)”
e2“Cytokinin increases the rate of greening”
Claim · model-written summary
Cytokinin enhanced tetrapyrrole metabolite levels.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Treatment
- cytokinine0
- Outcome
- steady-state levels of metabolites of the tetrapyrrole biosynthesis pathwaye0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The steady-state levels of metabolites of the tetrapyrrole biosynthesis pathway leading to the production of chlorophyll are enhanced by cytokinin”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Cytokinin modulated chlorophyll biosynthesis gene expression.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Treatment
- cytokinine0
- Gene
- HEMA1e0
- Outcome
- metabolite levelse0
- Qualifier
- modulation of expression for chlorophyll biosynthesis genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect of cytokinin on metabolite levels arises due to the modulation of expression for chlorophyll biosynthesis genes such as HEMA1, GUN4, GUN5, and CHLM”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
HEMA1 expression corresponded to higher glutamyl-tRNA reductase levels.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Gene
- HEMA1e0
- Outcome
- level of the encoded glutamyl-tRNA reductasee0
- Direction
- enhancede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased expression of HEMA1 is reflected in an enhanced level of the encoded glutamyl-tRNA reductase”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
AHK2 and AHK3 receptors played central roles in the transition.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Gene
- AHK2e0
- Outcome
- central role in this processe0
- Qualifier
- cytokinin receptorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the cytokinin receptors ARABIDOPSIS HIS KINASE2 (AHK2) and AHK3 play a central role in this process”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
ARR1, ARR10 and ARR12 mediated transcriptional output in the transition.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Gene
- ARR10e0
- Outcome
- transcriptional output during etioplast-chloroplast transitione0
- Qualifier
- mediatinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ARR1), ARR10, and ARR12 play an important role in mediating the transcriptional output during etioplast-chloroplast transition”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
B-type ARRs bound HEMA1 and LHCB6 promoters.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Gene
- B-type ARRse0
- Outcome
- bind to the promotors of HEMA1 and LHCB6 genese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B-type ARRs bind to the promotors of HEMA1 and LHCB6 genes”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Authors infer direct transcriptional regulation of chlorophyll biosynthesis and light-harvesting genes.
- Taxon
- Arabidopsis (Arabidopsis thaliana)Arabidopsis thalianae1
- Outcome
- genes of chlorophyll biosynthesis and the light harvesting complexe0
- Qualifier
- cytokinin-dependent transcription factorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin-dependent transcription factors directly regulate genes of chlorophyll biosynthesis and the light harvesting complex”
e1“Arabidopsis (Arabidopsis thaliana)”
The same questions in other papers
class · molecular: metabolites · Arabidopsis thaliana (thale cress)Positive and negative results
4 papers in the same direction as this paper · 3 in the opposite direction
- no effect
- no effect
- no effect
4 papers more in this group
See all 8 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.