Abstract
Optimal root architecture is established by multiple intrinsic (e.g. hormones) and extrinsic (e.g. gravity and touch) signals and is established, in part, by directed root growth. We show that asymmetrical exposure of cytokinin (CK) at the root tip in Arabidopsis (Arabidopsis thaliana) promotes cell elongation that is potentiated by glucose in a hexokinase-influenced, G protein-independent manner. This mode of CK signaling requires the CK receptor, ARABIDOPSIS HISTIDINE KINASE4 and, at a minimum, its cognate type B ARABIDOPSIS RESPONSE REGULATORS ARR1, ARR10, and ARR11 for full responsiveness, while type A response regulators act redundantly to attenuate this CK response. Ethylene signaling through the ethylene receptor ETHYLENE RESISTANT1 and its downstream signaling element ETHYLENE INSENSITIVE2 are required for CK-induced root cell elongation. Negative and positive feedback loops are reinforced by CK regulation of the expression of the genes encoding these elements in both the CK and ethylene signaling pathways. Auxin transport facilitated by PIN-FORMED2 as well as auxin signaling through control of the steady-state level of transcriptional repressors INDOLE-3-ACETIC ACID7 (IAA7), IAA14, and IAA17 via TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX PROTEIN are involved in CK-induced root cell elongation. This action lies downstream of ethylene and CK induction. Intrinsic signaling in this response operates independently of the extrinsic signal touch, although actin filament organization, which is important in the touch response, may be important for this response, since latrunculin B can induce similar growth. This root growth response may have adaptive significance, since CK responsiveness is inversely related to root coiling and waving, two root behaviors known to be important for fitness.
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Claims 10
Claim · model-written summary
Asymmetric cytokinin exposure promoted root cell elongation, potentiated by glucose.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- asymmetrical exposure of cytokinin (CK)e0
- Compound
- glucosee0
- Outcome
- cell elongatione0
- Direction
- promotese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“asymmetrical exposure of cytokinin (CK) at the root tip in Arabidopsis (Arabidopsis thaliana) promotes cell elongation that is potentiated by glucose”
Claim · model-written summary
Cytokinin signaling depended on hexokinase but was independent of G protein.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- hexokinasee0
- Outcome
- hexokinase-influenced, G protein-independent mannere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in a hexokinase-influenced, G protein-independent manner”
t0“Arabidopsis”
Claim · model-written summary
Full cytokinin responsiveness required ARABIDOPSIS HISTIDINE KINASE4 and type B response regulators.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ARABIDOPSIS HISTIDINE KINASE4e0
- Outcome
- full responsivenesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“requires the CK receptor, ARABIDOPSIS HISTIDINE KINASE4 and, at a minimum, its cognate type B ARABIDOPSIS RESPONSE REGULATORS ARR1, ARR10, and ARR11 for full responsiveness”
t0“Arabidopsis”
Claim · model-written summary
Type A response regulators attenuated the cytokinin response.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- type A response regulatorse0
- Outcome
- attenuate this CK responsee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“type A response regulators act redundantly to attenuate this CK response”
t0“Arabidopsis”
Claim · model-written summary
Ethylene signaling components were required for cytokinin-induced root elongation.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ETHYLENE RESISTANT1e0
- Outcome
- CK-induced root cell elongatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ethylene signaling through the ethylene receptor ETHYLENE RESISTANT1 and its downstream signaling element ETHYLENE INSENSITIVE2 are required for CK-induced root cell elongation”
t0“Arabidopsis”
Claim · model-written summary
Cytokinin regulated expression of cytokinin and ethylene signaling genes.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- expression of the genes encoding these elementse0
- Qualifier
- CK regulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CK regulation of the expression of the genes encoding these elements in both the CK and ethylene signaling pathways”
t0“Arabidopsis”
Claim · model-written summary
PIN-FORMED2 auxin transport and auxin signaling participated in root elongation.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- PIN-FORMED2e0
- Outcome
- CK-induced root cell elongatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Auxin transport facilitated by PIN-FORMED2 as well as auxin signaling through control of the steady-state level of transcriptional repressors INDOLE-3-ACETIC ACID7 (IAA7), IAA14, and IAA17 via TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX PROTEIN are involved in CK-induced root cell elongation”
t0“Arabidopsis”
Claim · model-written summary
The response was independent of touch signaling.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- Intrinsic signaling in this responsee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Intrinsic signaling in this response operates independently of the extrinsic signal touch”
t0“Arabidopsis”
Claim · model-written summary
Latrunculin B induced similar root growth.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- latrunculin Be0
- Outcome
- similar growthe0
- Direction
- inducee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“latrunculin B can induce similar growth”
t0“Arabidopsis”
Claim · model-written summary
Cytokinin responsiveness was inversely related to root coiling and waving.
- Taxon
- ArabidopsisArabidopsist0
- Compound
- CKe0
- Outcome
- root coiling and wavinge0
- Direction
- inverselye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CK responsiveness is inversely related to root coiling and waving”
t0“Arabidopsis”
The same questions in other papers
class · cytology · ArabidopsisPositive and negative results
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- no effect
- negative
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