Hydrotropism: Root Bending Does Not Require Auxin Redistribution

Shkolnik, Doron; Krieger, Gat; Nuriel, Roye; Fromm, Hillel

doi:10.1016/j.molp.2016.02.001

Cited by 54 publications

(68 citation statements)

References 11 publications

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“…Root hydrotropism and gravitropism differ in several aspects, such as the time of response (Eapen et al, 2005), the region of bending initiation (reported in this study), the involvement of auxin (Kaneyasu et al, 2007;Shkolnik et al, 2016), and the effect of ROS on the response kinetics. To elucidate the effects of ROS on tropic responses, their downstream effectors in gravitropism and hydrotropism need to be characterized.…”

Section: Discussionmentioning

confidence: 58%

“…In contrast, neither auxin redistribution nor auxin signaling are required for hydrotropic bending (Shkolnik et al, 2016). Moreover, inhibition of polar auxin transport or Transport Inhibitor Response 1-dependent signaling accelerates hydrotropism (Shkolnik et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

“…To study ROS dynamics during hydrotropic growth, wild-type seedlings were introduced into a moisture gradient in a closed CaCl 2 -containing chamber (herein referred to as the CaCl 2 / dry chamber) as previously described (Takahashi et al, 2002;Kobayashi et al, 2007;Shkolnik et al, 2016). Under this system, root bending upon hydrostimulation initiates at a region more distant from the root tip compared to root bending by gravitropism.…”

Section: Different Spatial and Temporal Ros Patterns Occur In Roots Imentioning

confidence: 99%

“…A CaCl 2 dry chamber was designed based on a previously described system (Takahashi et al, 2002;Kobayashi et al, 2007;Shkolnik et al, 2016) with the following modifications: Plates were prepared as described in "Plant Material and Growth Conditions" with or without supplemented chemicals, as indicated. The medium was cut 6 cm from the bottom and 5-to 7-d-old seedlings were transferred to the cut medium, such that approximately 0.2 mm of the primary root tip was bolting from the agar into air.…”

Section: Hydrotropic Stimulation Assaysmentioning

confidence: 99%

“…Moreover, mutants with a reduced response to gravity (pgm1) and to auxin (axr1 and axr2) exhibit higher responsiveness to hydrostimulation, manifested as accelerated bending compared to wild-type roots (Takahashi et al, 2002(Takahashi et al, , 2003. Recently, we have shown that hydrotropic root bending does not require auxin redistribution and is accelerated in the presence of auxin polar transport inhibitors and auxin-signaling antagonists (Shkolnik et al, 2016). These results reflect the competition, or interference, between root gravitropism and hydrotropism (Takahashi et al, 2009).…”

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confidence: 97%

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Reactive oxygen species tune root tropic responses

et al. 2016

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The default growth pattern of primary roots of land plants is directed by gravity. However, roots possess the ability to sense and respond directionally to other chemical and physical stimuli, separately and in combination. Therefore, these root tropic responses must be antagonistic to gravitropism. The role of reactive oxygen species (ROS) in gravitropism of maize and Arabidopsis (Arabidopsis thaliana) roots has been previously described. However, which cellular signals underlie the integration of the different environmental stimuli, which lead to an appropriate root tropic response, is currently unknown. In gravity-responding roots, we observed, by applying the ROS-sensitive fluorescent dye dihydrorhodamine-123 and confocal microscopy, a transient asymmetric ROS distribution, higher at the concave side of the root. The asymmetry, detected at the distal elongation zone, was built in the first 2 h of the gravitropic response and dissipated after another 2 h. In contrast, hydrotropically responding roots show no transient asymmetric distribution of ROS. Decreasing ROS levels by applying the antioxidant ascorbate, or the ROS-generation inhibitor diphenylene iodonium attenuated gravitropism while enhancing hydrotropism. Arabidopsis mutants deficient in Ascorbate Peroxidase 1 showed attenuated hydrotropic root bending. Mutants of the root-expressed NADPH oxidase RBOH C, but not rbohD, showed enhanced hydrotropism and less ROS in their roots apices (tested in tissue extracts with Amplex Red). Finally, hydrostimulation prior to gravistimulation attenuated the gravistimulated asymmetric ROS and auxin signals that are required for gravity-directed curvature. We suggest that ROS, presumably H 2 O 2 , function in tuning root tropic responses by promoting gravitropism and negatively regulating hydrotropism.

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Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 99%