Abstract
Brassinosteroids (BRs) are growth-promoting steroidal hormones. Despite the importance of BRs in plant biology, the signal that initiates BR biosynthesis remains unknown. Among the enzymes involved in BR biosynthesis in Arabidopsis (Arabidopsis thaliana), DWARF4 catalyzes the rate-determining step. Through both the histochemical analysis of DWF4pro:GUS plants and the direct measurement of endogenous BR content, we discovered that BR biosynthesis is stimulated by auxin. When DWF4pro:GUS was subjected to auxin dose-response tests and a time-course analysis, GUS activity started to increase at an auxin concentration of 10 nm, rising noticeably after 1 h of auxin treatment. In addition, the analysis of the DWF4pro:GUS line in BR- and auxin-mutant backgrounds revealed that the induction by auxin requires auxin-signaling pathways but not BRs, which implies that auxin signaling directly controls BR biosynthesis. Furthermore, chromatin immunoprecipitation assays confirmed that auxin inhibits the binding of the transcriptional repressor, BZR1, to the DWF4 promoter. A microarray analysis that was designed to examine the transcriptomes after treatment with auxin alone or auxin plus brassinazole (a BR biosynthetic inhibitor) revealed that genes previously characterized as being auxin responsive are not properly regulated when BR biosynthesis is disrupted by brassinazole. Therefore, our results support the idea that auxin regulates BR biosynthesis, and that auxin thus relies on synthesized BRs for some of its growth-promoting effects in Arabidopsis.
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 9
Claim · model-written summary
Auxin stimulated brassinosteroid biosynthesis.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- auxine1
- Outcome
- BR biosynthesise1
- Direction
- stimulatede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“BR biosynthesis is stimulated by auxin”
Claim · model-written summary
GUS activity increased beginning at 10 nm auxin.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxin concentration of 10 nme1
- Gene
- GUSe1
- Outcome
- GUS activitye1
- Direction
- increasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“GUS activity started to increase at an auxin concentration of 10 nm”
Claim · model-written summary
GUS activity rose noticeably after 1 h of auxin treatment.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxin treatmente1
- Outcome
- GUS activitye1
- Direction
- rising noticeablye1
- Qualifier
- after 1 he1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“GUS activity started to increase at an auxin concentration of 10 nm, rising noticeably after 1 h of auxin treatment”
Claim · model-written summary
Auxin induction required auxin-signaling pathways.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxine1
- Outcome
- induction by auxine1
- Qualifier
- auxin-signaling pathwayse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“the induction by auxin requires auxin-signaling pathways”
Claim · model-written summary
Auxin induction did not require brassinosteroids.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxine1
- Outcome
- BRse1
- Qualifier
- not BRse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“the induction by auxin requires auxin-signaling pathways but not BRs”
Claim · model-written summary
Auxin inhibited BZR1 binding to the DWF4 promoter.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxine1
- Gene
- BZR1e1
- Outcome
- binding of the transcriptional repressor, BZR1, to the DWF4 promotere1
- Direction
- inhibitse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“auxin inhibits the binding of the transcriptional repressor, BZR1, to the DWF4 promoter”
Claim · model-written summary
Auxin-responsive genes were not properly regulated when brassinosteroid synthesis was disrupted by brassinazole.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- brassinazolee1
- Outcome
- genes previously characterized as being auxin responsivee1
- Direction
- not properly regulatede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“genes previously characterized as being auxin responsive are not properly regulated when BR biosynthesis is disrupted by brassinazole”
Claim · model-written summary
The authors infer auxin signaling directly controls brassinosteroid biosynthesis.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxin signalinge1
- Outcome
- BR biosynthesise1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“auxin signaling directly controls BR biosynthesis”
Claim · model-written summary
The authors infer some auxin growth promotion relies on synthesized brassinosteroids.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- auxine1
- Outcome
- growth-promoting effectse1
- Qualifier
- synthesized BRse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis (Arabidopsis thaliana)”
e1“auxin thus relies on synthesized BRs for some of its growth-promoting effects in Arabidopsis”
The same questions in other papers
class · molecular: metabolites · ArabidopsisPositive and negative results
6 papers in the same direction as this paper · 5 in the opposite direction
- positive
- no effect
- no effect
8 papers more in this group
See all 12 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
- negative
- negative
- negative
71 papers more in this group
See all 75 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.