Cytokinin, Acting through Ethylene, Restores Gravitropism to Arabidopsis Seedlings Grown under Red Light

Golan, Amnon; Tepper, Michal; Soudry, Esther; Horwitz, Benjamin A.; Gepstein, Shimon

doi:10.1104/pp.112.3.901

Cited by 45 publications

(32 citation statements)

References 18 publications

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“…CK has been previously shown to be involved in ethylene biosynthesis by stabilizing the ethylene biosynthesis enzyme ACS5 (Vogel et al, 1998a(Vogel et al, , 1998bChae et al, 2003;Hansen et al, 2009). A number of CK-related responses have been shown to be mediated by ethylene (Cary et al, 1995;Golan et al, 1996;Tanaka et al, 2006). However, in the root growth response described here, increased ethylene production had only a small effect.…”

Section: The Mechanism Revealed Through Genetic Dissectioncontrasting

confidence: 47%

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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Section: The Mechanism Revealed Through Genetic Dissectioncontrasting

confidence: 47%

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

2011

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“…Cytokinin and BRs act antagonistically to each other in controlling lightmediated seedling development (Chory et al, 1994). Cytokinin signaling mediated by ethylene signaling has also been previously shown to restore gravitropism to red-light-grown randomized Arabidopsis hypocotyls (Golan et al, 1996). A number of BR-related responses are mediated by ethylene.…”

Section: Discussionmentioning

confidence: 99%

Hypocotyl Directional Growth in Arabidopsis: A Complex Trait

et al. 2012

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The growth direction of the Arabidopsis (Arabidopsis thaliana) etiolated-seedling hypocotyl is a complex trait that is controlled by extrinsic signals such as gravity and touch as well as intrinsic signals such as hormones (brassinosteroid [BR], auxin, cytokinin, ethylene) and nutrient status (glucose [Glc], sucrose). We used a genetic approach to identify the signaling elements and their relationship underlying hypocotyl growth direction. BR randomizes etiolated-seedling growth by inhibiting negative gravitropism of the hypocotyls via modulating auxin homeostasis for which we designate as reset, not to be confused with the gravity set point angle. Cytokinin signaling antagonizes this BR reset of gravity sensing and/or tropism by affecting ethylene biosynthesis/signaling. Glc also antagonizes BR reset but acts independently of cytokinin and ethylene signaling pathways via inhibiting BR-regulated gene expression quantitatively and spatially, by altering protein degradation, and by antagonizing BR-induced changes in microtubule organization and cell patterning associated with hypocotyl agravitropism. This BR reset is reduced in the presence of the microtubule organization inhibitor oryzalin, suggesting a central role for cytoskeleton reorganization. A unifying and hierarchical model of Glc and hormone signaling interplay is proposed. The biological significance of BR-mediated changes in hypocotyl graviresponse lies in the fact that BR signaling sensitizes the dark-grown seedling hypocotyl to the presence of obstacles, overriding gravitropism, to enable efficient circumnavigation through soil.

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“…Wild-type Arabidopsis seedlings also show a dramatic effect of light on gravitropism ( Fig. 1) in that they display randomly orientated growth in response to R (Liscum & Hangarter 1993;Golan et al 1996;Poppe et al 1996;Robson & Smith 1996). Tobacco seedlings also display randomly orientated hypocotyls under continuous R (M.-R. Cha & R.P.…”

Section: Phytochrome and Gravitropismmentioning

confidence: 99%

Gravity, light and plant form

Hangarter

1997

Plant Cell & Environment

182

124

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Plants have evolved highly sensitive and selective mechanisms that detect and respond to various aspects of their environment. As a plant develops, it integrates the environmental information perceived by all of its sensory systems and adapts its growth to the prevailing environmental conditions. Light is of critical importance because plants depend on it for energy and, thus, survival. The quantity, quality and direction of light are perceived by several different photosensory systems that together regulate nearly all stages of plant development, presumably in order to maintain photosynthetic efficiency. Gravity provides an almost constant stimulus that is the source of critical spatial information about its surroundings and provides important cues for orientating plant growth. Gravity plays a particularly important role during the early stages of seedling growth by stimulating a negative gravitropic response in the primary shoot that orientates it towards the source of light, and a positive gravitropic response in the primary root that causes it to grow down into the soil, providing support and nutrient acquisition. Gravity also influences plant form during later stages of development through its effect on lateral organs and supporting structures. Thus, the final form of a plant depends on the cumulative effects of light, gravity and other environmental sensory inputs on endogenous developmental programs. This article is focused on developmental interactions modulated by light and gravity.

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Cytokinin, Acting through Ethylene, Restores Gravitropism to Arabidopsis Seedlings Grown under Red Light

Cited by 45 publications

References 18 publications

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

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

Hypocotyl Directional Growth in Arabidopsis: A Complex Trait

Gravity, light and plant form

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