Abstract
The timely transition of vegetative to reproductive development is coordinated through quantitative regulation of floral pathway genes in response to physiological and environmental cues. Here, we show that the circadian-controlled expression of the Arabidopsis thaliana floral transition regulators FLOWERING LOCUS T (FT) and CONSTANS (CO) is antiphasic to that of BBX19, a transcription factor with two B-Box motifs. Diminished expression of BBX19 by RNA interference accelerates flowering, and constitutive expression of BBX19 delays flowering under inductive photoperiods. This delay is not accompanied by the alteration of CO expression levels but rather by a reduction of transcript levels of FT and the FT-regulated genes SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1, LEAFY, and FRUITFUL. Similar to CO, BBX19 is expressed in vasculature. BBX19 and CO colocalize in the nucleus and interact physically in vivo. In transient assays, coinfiltration of 10-fold more CO overcomes the BBX19-mediated repression of FT activation. Substitution of the conserved Cys-25 to Ser in the BBX19 Box1 motif abolishes the BBX19-CO interaction and eliminates the negative regulation of flowering time, while the analogous C76S substitution in the Box2 motif is ineffective. Together, these results implicate BBX19 as a circadian clock output that depletes the active CO pool to accurately monitor daylength and precisely time FT expression.
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Claims 12
Claim · model-written summary
FT and CO expression is antiphasic to BBX19 expression.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Gene
- BBX19e0
- Outcome
- expression of the Arabidopsis thaliana floral transition regulators FLOWERING LOCUS T (FT) and CONSTANS (CO)e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the circadian-controlled expression of the Arabidopsis thaliana floral transition regulators FLOWERING LOCUS T (FT) and CONSTANS (CO) is antiphasic to that of BBX19”
Claim · model-written summary
Reduced BBX19 expression accelerates flowering.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- RNA interferencee0
- Gene
- BBX19e0
- Outcome
- floweringe0
- Direction
- acceleratese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Diminished expression of BBX19 by RNA interference accelerates flowering”
e1“Arabidopsis thaliana”
Claim · model-written summary
Constitutive BBX19 expression delays flowering under inductive photoperiods.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- constitutive expression of BBX19e0
- Gene
- BBX19e0
- Outcome
- floweringe0
- Direction
- delayse0
- Qualifier
- under inductive photoperiodse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“constitutive expression of BBX19 delays flowering under inductive photoperiods”
e1“Arabidopsis thaliana”
Claim · model-written summary
Constitutive BBX19 expression did not alter CO expression levels.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- constitutive expression of BBX19e2
- Gene
- COe0
- Outcome
- CO expression levelse0
- Direction
- not accompanied by the alteratione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This delay is not accompanied by the alteration of CO expression levels”
e1“Arabidopsis thaliana”
e2“constitutive expression of BBX19 delays flowering”
Claim · model-written summary
Constitutive BBX19 expression reduced FT and FT-regulated gene transcript levels.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- constitutive expression of BBX19e2
- Outcome
- transcript levels of FT and the FT-regulated genes SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1, LEAFY, and FRUITFULe0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a reduction of transcript levels of FT and the FT-regulated genes SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1, LEAFY, and FRUITFUL”
e1“Arabidopsis thaliana”
e2“constitutive expression of BBX19 delays flowering”
Claim · model-written summary
BBX19 is expressed in vasculature.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- vasculaturee0
- Gene
- BBX19e0
- Outcome
- expressed in vasculaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar to CO, BBX19 is expressed in vasculature”
e1“Arabidopsis thaliana”
Claim · model-written summary
BBX19 and CO colocalize in the nucleus.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- BBX19 and COe0
- Outcome
- colocalize in the nucleuse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“BBX19 and CO colocalize in the nucleus”
e1“Arabidopsis thaliana”
Claim · model-written summary
BBX19 and CO interact physically in vivo.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- BBX19 and COe0
- Outcome
- interact physically in vivoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“BBX19 and CO colocalize in the nucleus and interact physically in vivo”
e1“Arabidopsis thaliana”
Claim · model-written summary
Tenfold more CO overcomes BBX19-mediated repression of FT activation in transient assays.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- coinfiltration of 10-fold more COe0
- Outcome
- BBX19-mediated repression of FT activatione0
- Direction
- overcomese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In transient assays, coinfiltration of 10-fold more CO overcomes the BBX19-mediated repression of FT activation”
e1“Arabidopsis thaliana”
Claim · model-written summary
The BBX19 Box1 Cys-25-to-Ser substitution abolished interaction with CO.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Substitution of the conserved Cys-25 to Ser in the BBX19 Box1 motife0
- Outcome
- BBX19-CO interactione0
- Direction
- abolishese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Substitution of the conserved Cys-25 to Ser in the BBX19 Box1 motif abolishes the BBX19-CO interaction”
e1“Arabidopsis thaliana”
Claim · model-written summary
The BBX19 Box1 Cys-25-to-Ser substitution eliminated negative regulation of flowering time.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Substitution of the conserved Cys-25 to Ser in the BBX19 Box1 motife0
- Outcome
- negative regulation of flowering timee0
- Direction
- eliminatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Substitution of the conserved Cys-25 to Ser in the BBX19 Box1 motif abolishes the BBX19-CO interaction and eliminates the negative regulation of flowering time”
e1“Arabidopsis thaliana”
Claim · model-written summary
The analogous Box2 C76S substitution was ineffective.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- C76S substitution in the Box2 motife0
- Outcome
- ineffectivee0
- Direction
- ineffectivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the analogous C76S substitution in the Box2 motif is ineffective”
e1“Arabidopsis thaliana”
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