Abstract
Cytokinins regulate diverse aspects of plant development. They are perceived by membrane-localised receptors that transmit a signal to nuclear-localised response regulators via the Histidine Phosphotransfer proteins (HPts). These HPts can be divided into two classes: authentic HPts (AHPs), which positively regulate cytokinin signalling, and pseudo HPts (PHPs), which inhibit it. Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade, AHP4 evolved separately and is more closely related to the monocot PHPs than to the dicot AHPs. AHP4's role in cytokinin signalling has been ambiguous; in some cases, it has been shown to act as a positive regulator, whilst in others, it acts negatively. Here, we propose that AHP4 act like a dimmer switch to dampen cytokinin output. Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development. However, AHP4 expression is induced under osmotic stress, and under this condition, we show a novel role for AHP4 in reducing cytokinin signalling in the phloem and maintaining primary root growth. We propose that AHP4 fine-tunes responses to the osmotic environment by attenuating cytokinin signalling.
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Claims 6
Claim · model-written summary
AHP4 expression is induced under osmotic stress compared with optimal growth conditions in Arabidopsis.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- osmotic stresse1
- Gene
- AHP4e1
- Outcome
- AHP4 expressione1
- Direction
- inducede1
- Comparator
- optimal growth conditionse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e1“AHP4 expression is induced under osmotic stress”
e2“Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development”
Claim · model-written summary
Under optimal growth conditions, AHP4 has little effect on cytokinin signalling or plant development in Arabidopsis.
- Taxon
- ArabidopsisArabidopsise0
- Gene
- AHP4e2
- Outcome
- cytokinin signalling or plant developmente2
- Qualifier
- Under optimal growth conditionse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e2“Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development”
Claim · model-written summary
Under optimal growth conditions, AHP4 is expressed at a low level in phloem companion cells of Arabidopsis.
- Taxon
- ArabidopsisArabidopsise0
- Organ / stage
- phloem companion cellse2
- Gene
- AHP4e2
- Outcome
- expressed at a low levele2
- Qualifier
- Under optimal growth conditionse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e2“Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development”
Claim · model-written summary
Under osmotic stress, AHP4 reduces cytokinin signalling in the phloem of Arabidopsis.
- Taxon
- ArabidopsisArabidopsise0
- Organ / stage
- phloeme3
- Treatment
- osmotic stresse1
- Gene
- AHP4e3
- Outcome
- cytokinin signallinge3
- Direction
- reducinge3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e1“AHP4 expression is induced under osmotic stress”
e3“under this condition, we show a novel role for AHP4 in reducing cytokinin signalling in the phloem and maintaining primary root growth”
Claim · model-written summary
Under osmotic stress, AHP4 maintains primary root growth in Arabidopsis.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- osmotic stresse1
- Gene
- AHP4e3
- Outcome
- primary root growthe3
- Direction
- maintaininge3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e1“AHP4 expression is induced under osmotic stress”
e3“under this condition, we show a novel role for AHP4 in reducing cytokinin signalling in the phloem and maintaining primary root growth”
Claim · model-written summary
AHP4 fine-tunes responses to the osmotic environment in Arabidopsis by attenuating cytokinin signalling.
- Taxon
- ArabidopsisArabidopsise0
- Gene
- AHP4e4
- Outcome
- responses to the osmotic environmente4
- Qualifier
- by attenuating cytokinin signallinge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade”
e4“We propose that AHP4 fine-tunes responses to the osmotic environment by attenuating cytokinin signalling”
The same questions in other papers
drought · growth · ArabidopsisPositive and negative results
1 paper in the same direction as this paper · 10 in the opposite direction
- negative
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