Hydrotropism Interacts with Gravitropism by Degrading Amyloplasts in Seedling Roots of Arabidopsis and Radish

Takahashi, Nobuyuki

doi:10.1104/pp.102.018853

Cited by 40 publications

(39 citation statements)

References 18 publications

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“…Histochemical staining, observation and measurement of amyloplasts in the columella cells of the root cap were performed as described by Takahashi et al . (). Images were obtained using an Olympus BX51 optical microscope equipped with differential interference contrast (DIC) for observation and an Olympus DP71 system for photography (Olympus Optical, Tokyo, Japan).…”

Section: Methodssupporting

confidence: 84%

“…a,b), probably by increasing cells with columella identity in the root cap (Harrison & Masson, ). As amyloplast degradation is well known to be involved in a variety of environmental stress responses (Takahashi et al ., ), we proceeded to test whether the sensitivity of gsa‐1 root gravitropism to NH 4 + was associated with accelerated degradation of amyloplasts under NH 4 + stress. At shorter NH 4 + exposure times (< 24 h), no rapid degradation of amyloplasts was observed in the columella cells of Col‐0.…”

Section: Resultsmentioning

confidence: 99%

“…Here, we report a novel Arabidopsis thaliana mutant, gsa‐1 ( g ravitropism s ensitive to a mmonium‐ 1 ) , which displays reduced root gravitropism in response to NH 4 + stress. Gene cloning shows gsa‐1 to be allelic to ARG1 ( A LTERED R ESPONSE TO G RAVITY 1 ), which is required for the establishment of the lateral auxin gradient across the root cap following gravistimulation (Boonsirichai et al ., ; Harrison & Masson, ).Our results further demonstrate that the disruption of GSA‐1 / ARG1 can reduce basipetal auxin transport and the expression of AUX1 protein in root apices. Moreover, we demonstrate the involvement of PIN2 in the NH 4 + regulation of the gravitropic response.…”

Section: Introductionmentioning

confidence: 97%

“…Given that the appropriate distribution of roots within the soil greatly affects plant survival, roots have evolved to sense adverse environmental cues and to modulate their growth direction through a variety of pathways. For example, moisture gradients and water stress can cause the desensitization of gravitropism in Arabidopsis by the degradation of amyloplasts in root columella cells, allowing roots to exhibit positive hydrotropism (Takahashi et al ., ). Similarly, roots exposed to salt stress show inhibited gravitropism, which permits the active avoidance of stressed regions (Li & Zhang, ; Sun et al ., ).…”

Section: Introductionmentioning

confidence: 99%

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GSA‐1/ARG1 protects root gravitropism in Arabidopsis under ammonium stress

Zou

Chen

et al. 2013

New Phytologist

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SummaryGravitropism plays a critical role in plant growth and development, plant stability and acclimation to changes in water and nutrient availability. Ammonium (NH 4 + ) is well known to have profound effects on root growth, but its impacts on gravitropism are poorly understood.To determine which genes are essential for the maintenance of root gravitropism under NH 4 + stress, we isolated and identified an NH 4 + -sensitive mutant, gsa-1 (gravitropism sensitive to ammonium-1), in Arabidopsis thaliana, using an agar plate root reorientation assay. We found that, under NH 4 + stress, gsa-1 displayed increased loss of root gravitropism. Gene cloning and sequencing revealed that gsa-1 contains a G to C transversion mutation at the highly conserved 5′-GT splice position of intron 10 of ARG1 (ALTERED RESPONSE TO GRAVITY1), known to participate in the transduction of the root gravity signal. Genetic complement tests established the locus of GSA-1/ARG1 and its role in resistance to NH 4 + inhibition on root gravitropism. GSA-1/ARG1 is required for normal AUX1 expression and basipetal auxin transport in root apices. In addition, PIN-FORMED2 (PIN2) is proposed as a target in the reduction of root gravitropism under NH 4 + stress, a response which can be antagonized by the GSA-1/ARG1-dependent pathway. These results suggest that GSA-1/ARG1 protects root gravitropism in Arabidopsis thaliana under ammonium stress.

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Section: Methodssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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GSA‐1/ARG1 protects root gravitropism in Arabidopsis under ammonium stress

Zou

Chen

et al. 2013

New Phytologist

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“…For instance, starch deficient pgm1 mutants lack a normal response to gravistimulation [17], while the starch excess mutant sex1 displays an increased sensitivity to gravistimulation [18]. Moisture gradient or water stress caused immediate degradation of amyloplasts in root columella cells of Arabidopsis [19]. In this study, the levels of starch grain were reduced by EA treat ment.…”

Section: Ea Reduced the Starch Grain In Arabidopsis Root Capsmentioning

confidence: 69%

The effect of ellagic acid on the root gravitropic response in Arabidopsis thaliana

Yan

Jin

Wang

et al. 2015

Russ J Plant Physiol

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Gravitropism is affected by many exogenous factors such as environmental stresses. In the present study, the effect of ellagic acid (EA) on the gravitropic curvature of Arabidopsis thaliana (L.) Heynh. roots was characterized. Exogenous application of EA influenced root gravitropic responses in a concentration depen dent fashion. KI/I staining research revealed that the starch grain in the root cap was reduced by EA treat ments. Simultaneously, expression of auxin responsive reporter gene DR5::GFP showed that the auxin redis tribution in roots treated with EA was less sensitive to that of control groups under gravity stimulus. Moreover, the expression of one of the auxin flux facilitators-PIN2, was also suppressed by EA. Taken together, our results indicated that the effects of EA on root gravitropism were largely dependent on the reduction of starch grain and the disorder of lateral auxin redistribution.Abbreviations: Col-Columbia; EA-ellagic acid; GFP-green fluorescent protein.

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Molecular mechanisms of root gravity sensing and signal transduction

Strohm

Baldwin

Masson

2011

WIREs Developmental Biology

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Plants use gravity as a guide to direct their roots down into the soil to anchor themselves and to find resources needed for growth and development. In higher plants, the columella cells of the root tip form the primary site of gravity sensing, and in these cells the sedimentation of dense, starch-filled plastids (amyloplasts) triggers gravity signal transduction. This generates an auxin gradient across the root cap that is transmitted to the elongation zone where it promotes differential cell elongation, allowing the root to direct itself downward. It is still not well understood how amyloplast sedimentation leads to auxin redistribution. Models have been proposed to explain how mechanosensitive ion channels or ligand-receptor interactions could connect these events. Although their roles are still unclear, possible second messengers in this process include protons, Ca(2+), and inositol 1,4,5-triphosphate. Upon gravistimulation, the auxin efflux facilitators PIN3 and PIN7 relocalize to the lower side of the columella cells and mediate auxin redistribution. However, evidence for an auxin-independent secondary mechanism of gravity sensing and signal transduction suggests that this physiological process is quite complex. Furthermore, plants must integrate a variety of environmental cues, resulting in multifaceted relationships between gravitropism and other directional growth responses such as hydro-, photo-, and thigmotropism.

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Hydrotropism Interacts with Gravitropism by Degrading Amyloplasts in Seedling Roots of Arabidopsis and Radish

Cited by 40 publications

References 18 publications

GSA‐1/ARG1 protects root gravitropism in Arabidopsis under ammonium stress

GSA‐1/ARG1 protects root gravitropism in Arabidopsis under ammonium stress

The effect of ellagic acid on the root gravitropic response in Arabidopsis thaliana

Molecular mechanisms of root gravity sensing and signal transduction

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