1. Molecular Mechanisms of Root Gravitropism
Shih-Heng Su, Nicole M. Gibbs, Amy L. Jancewicz, Patrick H. Masson 
Current Biology 
Volume 27, Issue 17, Pages R964-R972 (September 2017)
DOI: /j.cub
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2. Figure 1
Arabidopsis seedling root and hypocotyl develop opposite curvature responses to gravistimulation.
Overlaid images of a 4-day old Arabidopsis seedling (Col ecotype) responding to gravistimulation. Images were taken every 90 minutes. Overlaid images are false-colored differently with photoshop to better illustrate organ bending. This panel was inspired by [83].
Current Biology  , R964-R972DOI: ( /j.cub )
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3. Figure 2
Gravity stimulation alters the patterns of auxin transport along the root tip.
Serial diagrams illustrating auxin-transport patterns in vertical Arabidopsis root tips (A) and those stimulated with gravity (B,C). Each drawing represents the auxin transport pattern expected for a root whose tip angle from the gravity vector (α) is within the range indicated under the root. Red arrows illustrate the direction of auxin transport. Their widths represent the relative level of auxin flux. The columella cells (primary site of gravity sensing) are shown in pink. An asterisk marks a columella cell within the second tier of the root cap, whose molecular responses to gravistimulation are illustrated in Figure 3. The root epidermis is shaded in yellow. The gravitropic curvature (B and C) occurs at the distal side of the elongation zone.
Current Biology  , R964-R972DOI: ( /j.cub )
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4. Figure 3
Gravisensing promotes amyloplast sedimentation, cytoplasmic alkalinization, and a polarization of PIN auxin efflux carriers within the statocytes.
Molecular changes that occur in a second-tier columella cell of the root cap (asterisk in Figure 2) before gravity sensing and at different times following seedling reorientation within the gravity field. The approximate time elapsed after reorientation is indicated at the top left of each panel. For each reported time point, root-tip orientation and curvature are illustrated by a representative picture at the bottom right of the panel. Quickly sedimenting amyloplasts are shown by grey circles. The fast change in cytoplasmic pH that occurs in the columella cell in response to gravistimulation is shown by a change of color, from pink/purple (which represents the resting pH of ∼7.1) to red (representing an alkaline pH of ∼7.6). The gravity-induced changes in directional auxin efflux from the cell are represented by changes in the widths of the red arrows (15m panel). Each arrow represents the auxin efflux in the direction indicated by the arrowhead. The illustrated increase in downward auxin efflux from this statocyte derives from a relocalization of the PIN3 (green symbol) and PIN7 (blue symbol) auxin efflux carriers to the lower side of the cell. The last two panels (3h and 6h) show the same columella cell after the root tip has passed the tipping-point angle of 50° from the gravity vector. Amyloplasts have returned to their initial distal side of the statocyte. The PIN3 and PIN7 proteins have returned to symmetrical distribution on all sides of the cell, and auxin flow is no longer asymmetrical.
Current Biology  , R964-R972DOI: ( /j.cub )
Copyright © 2017 Elsevier Ltd Terms and Conditions