Cytokinin signal perception and transduction

Heyl, Alexander; Schmülling, Thomas

doi:10.1016/s1369-5266(03)00087-6

Cited by 216 publications

(155 citation statements)

References 57 publications

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“…The ER localization of the cytokinin receptors contrasts with the previous prediction that the cytokinin-binding CHASE domain is apoplastic (Inoue et al, 2001;Ueguchi et al, 2001) and with current models of cytokinin signaling assuming the localization of cytokinin receptors at the PM (Heyl and Schmü lling, 2003;Hwang and Sakakibara, 2006;Mü ller and Sheen, 2007;To and Kieber, 2008). However, it should be noted that a localization of a minor but functionally relevant part of the receptor pool at the PM cannot be excluded (Fig.…”

Section: Discussioncontrasting

confidence: 89%

“…Cytokinin receptors located on the ER membrane could transmit the cytokinin signal via AHP to the nucleus, similar to the way it is proposed for signal transmission from the PM (Schaller et al, 1995;Hwang and Sheen, 2001;Heyl and Schmü lling, 2003;Kakimoto, 2003;Bishopp et al, 2006). One benefit of the localization of receptors on endomembranes is that it may alleviate disadvantages caused by the variable intracellular distances that signaling chains have to bridge (Geldner and Robatzek, 2008).…”

Section: A Modified Model For Cytokinin Signalingmentioning

confidence: 90%

“…They also function in mediating the plant response to environmental signals, such as biotic and abiotic stresses (Argueso et al, 2009;Werner and Schmü lling, 2009). The cytokinin signal is perceived by membrane-bound sensor His kinases and further transduced by a multistep variant of the two-component signaling system (Heyl and Schmü lling, 2003;Kakimoto, 2003;Bishopp et al, 2006). Cytokinin receptors consist of an extracytosolic cyclase, His kinase-associated sensory extracellular (CHASE) domain flanked by two transmembrane domains at the N terminus, followed toward the C terminus by a His kinase and a response regulator domain in the predicted cytosolic part.…”

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confidence: 99%

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The Cytokinin Receptors of Arabidopsis Are Located Mainly to the Endoplasmic Reticulum

et al. 2011

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The plant hormone cytokinin is perceived by membrane-located sensor histidine kinases. Arabidopsis (Arabidopsis thaliana) possesses three cytokinin receptors: ARABIDOPSIS HISTIDINE KINASE2 (AHK2), AHK3, and CYTOKININ RESPONSE1/ AHK4. The current model predicts perception of the cytokinin signal at the plasma membrane. However, cytokinin-binding studies with membrane fractions separated by two-phase partitioning showed that in the wild type, as well as in mutants retaining only single cytokinin receptors, the major part of specific cytokinin binding was associated with endomembranes. Leaf epidermal cells of tobacco (Nicotiana benthamiana) expressing receptor-green fluorescent protein fusion proteins and bimolecular fluorescence complementation analysis showed strong fluorescence of the endoplasmic reticulum (ER) network for all three receptors. Furthermore, separation of the microsomal fraction of Arabidopsis plants expressing Myc-tagged AHK2 and AHK3 receptors by sucrose gradient centrifugation followed by immunoblotting displayed the Mg 2+ -dependent density shift typical of ER membrane proteins. Cytokinin-binding assays, fluorescent fusion proteins, and biochemical fractionation all showed that the large majority of cytokinin receptors are localized to the ER, suggesting a central role of this compartment in cytokinin signaling. A modified model for cytokinin signaling is proposed.

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Section: Discussioncontrasting

confidence: 89%

Section: A Modified Model For Cytokinin Signalingmentioning

confidence: 90%

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The Cytokinin Receptors of Arabidopsis Are Located Mainly to the Endoplasmic Reticulum

et al. 2011

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“…It is generally believed that cytokinin executes these physiological activities by regulating cell division and cell differentiation through a two-component system (TCS) signaling pathway (Hwang et al, 2002;Heyl and Schmü lling, 2003;Kakimoto, 2003;Ferreira and Kieber, 2005;Mü ller and Sheen, 2007). Key components of the TCS have been well defined by genetic and biochemical studies.…”

Section: Introductionmentioning

confidence: 99%

ArabidopsisHistidine Kinase CKI1 Acts Upstream of HISTIDINE PHOSPHOTRANSFER PROTEINS to Regulate Female Gametophyte Development and Vegetative Growth

et al. 2010

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Cytokinin signaling is mediated by a multiple-step phosphorelay. Key components of the phosphorelay consist of the histidine kinase (HK)-type receptors, histidine phosphotransfer proteins (HP), and response regulators (RRs). Whereas overexpression of a nonreceptor-type HK gene CYTOKININ-INDEPENDENT1 (CKI1) activates cytokinin signaling by an unknown mechanism, mutations in CKI1 cause female gametophytic lethality. However, the function of CKI1 in cytokinin signaling remains unclear. Here, we characterize a mutant allele, cki1-8, that can be transmitted through female gametophytes with low frequency (;0.17%). We have recovered viable homozygous cki1-8 mutant plants that grow larger than wild-type plants, show defective megagametogenesis and rarely set enlarged seeds. We found that CKI1 acts upstream of AHP (Arabidopsis HP) genes, independently of cytokinin receptor genes. Consistently, an ahp1,2-2,3,4,5 quintuple mutant, which contains an ahp2-2 null mutant allele, exhibits severe defects in megagametogenesis, with a transmission efficiency of <3.45% through female gametophytes. Rarely recovered ahp1,2-2,3,4,5 quintuple mutants are seedling lethal. Finally, the female gametophytic lethal phenotype of cki1-5 (a null mutant) can be partially rescued by IPT8 or ARR1 (a type-B Arabidopsis RR) driven by a CKI1 promoter. These results define a genetic pathway consisting of CKI1, AHPs, and type-B ARRs in the regulation of female gametophyte development and vegetative growth.

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“…CK signaling follows a multiple-step phosphorelay cascade (Heyl and Schmü lling, 2003;Mü ller and Sheen, 2007;To and Kieber, 2008;Werner and Schmü lling, 2009;Kieber and Schaller, 2010;Perilli et al, 2010;Mü ller, 2011) (Hwang and Sheen, 2001). CK is known to interact with other hormones so as to affect plant growth and development.…”

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confidence: 99%

Cytokinin Interplay with Ethylene, Auxin, and Glucose Signaling Controls Arabidopsis Seedling Root Directional Growth

2011

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(A.M.J.) 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 proteinindependent 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 CKinduced 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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Cytokinin signal perception and transduction

Cited by 216 publications

References 57 publications

The Cytokinin Receptors of Arabidopsis Are Located Mainly to the Endoplasmic Reticulum

The Cytokinin Receptors of Arabidopsis Are Located Mainly to the Endoplasmic Reticulum

ArabidopsisHistidine Kinase CKI1 Acts Upstream of HISTIDINE PHOSPHOTRANSFER PROTEINS to Regulate Female Gametophyte Development and Vegetative Growth

Cytokinin Interplay with Ethylene, Auxin, and Glucose Signaling Controls Arabidopsis Seedling Root Directional Growth

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