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 12
Claim · model-written summary
Asymmetric cytokinin at the Arabidopsis root tip promotes cell elongation.
- Taxon
- Arabidopsis (Arabidopsis thaliana)
Arabidopsis thalianae0 - Organ / stage
- root tipe0
- Treatment
- cytokinin (CK)e0
- 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”
Claim · model-written summary
Glucose potentiates cytokinin-induced root cell elongation.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- glucosee0
- Outcome
- cell elongatione0
- Direction
- potentiatede0
- Qualifier
- hexokinase-influenced, G protein-independent mannere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“promotes cell elongation that is potentiated by glucose in a hexokinase-influenced, G protein-independent manner”
t0“Arabidopsis”
Claim · model-written summary
Full cytokinin responsiveness requires AHK4 and ARR1, ARR10 and ARR11.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ARABIDOPSIS HISTIDINE KINASE4e0
- Outcome
- full responsivenesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
t0“Arabidopsis”
Claim · model-written summary
Type A response regulators redundantly attenuate the cytokinin response.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- type A response regulatorse0
- Outcome
- 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 receptor ETR1 and EIN2 are required for cytokinin-induced root cell 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 regulates expression of genes in cytokinin and ethylene pathways, reinforcing feedback loops.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- Negative and positive feedback loopse0
- Qualifier
- CK regulation of the expression of the genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
t0“Arabidopsis”
Claim · model-written summary
PIN-FORMED2-mediated auxin transport participates in cytokinin-induced root cell 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
Auxin signaling through IAA7, IAA14 and IAA17 control participates in cytokinin-induced elongation.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- INDOLE-3-ACETIC ACID7 (IAA7), IAA14, and IAA17e0
- Outcome
- CK-induced root cell elongatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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
This auxin response lies downstream of ethylene and cytokinin induction.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- This actione0
- Qualifier
- downstream of ethylene and CK inductione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This action lies downstream of ethylene and CK induction”
t0“Arabidopsis”
Claim · model-written summary
The intrinsic response operates independently of touch.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- touche0
- 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 can induce 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 is inversely related to root coiling and waving.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- CKe0
- Outcome
- root coiling and wavinge0
- Direction
- inversely relatede0
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”
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