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Light-Regulated Hypocotyl Elongation Involves Proteasome-Dependent Degradation of the Microtubule Regulatory Protein WDL3 in Arabidopsis

Xiaomin Liu, Tao Qin, Qianqian Ma, Jingbo Sun, Ziqiang Liu, Ming Yuan and Tonglin Mao
The Plant Cell
Vol. 25, No. 5 (MAY 2013), pp. 1740-1755
Stable URL: http://www.jstor.org/stable/23481915
Page Count: 16
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Light-Regulated Hypocotyl Elongation Involves Proteasome-Dependent Degradation of the Microtubule Regulatory Protein WDL3 in Arabidopsis
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Abstract

Light significantly inhibits hypocotyl cell elongation, and dark-grown seedlings exhibit elongated, etiolated hypocotyls. Microtubule regulatory proteins function as positive or negative regulators that mediate hypocotyl cell elongation by altering microtubule organization. However, it remains unclear how plants coordinate these regulators to promote hypocotyl growth in darkness and inhibit growth in the light. Here, we demonstrate that WAVE-DAMPENED 2—LIKE3 (WDL3), a microtubule regulatory protein of the WVD2/WDL family from Arabidopsis thaliana, functions in hypocotyl cell elongation and is regulated by a ubiquitin-26S proteasome—dependent pathway in response to light. WDL3 RNA interference Arabidopsis seedlings grown in the light had much longer hypocotyls than controls. Moreover, WDL3 overexpression resulted in overall shortening of hypocotyl cells and stabilization of cortical microtubules in the light. Cortical microtubule reorganization occurred slowly in cells from WDL3 RNA interference transgenic lines but was accelerated in cells from WDL3-overexpressing seedlings subjected to light treatment. More importantly, WDL3 protein was abundant in the light but was degraded through the 26S proteasome pathway in the dark. Overexpression of WDL3 inhibited etiolated hypocotyl growth in regulatory particle non-ATPase subunit-1a mutant (rpn1a-4) plants but not in wild-type seedlings. Therefore, a ubiquitin-26S proteasome—dependent mechanism regulates the levels of WDL3 in response to light to modulate hypocotyl cell elongation.

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