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DEVELOPMENT AND HORMONE ACTION

Genetic Dissection of Hormonal Responses in the Roots of Arabidopsis Grown under Continuous Mechanical Impedance^1,[W],[OA]

Center for Supports to Research and Education Activities Isotope Division (T.O., S.T.) and Graduate School of Science and Technology (S.T., Y. Obana, H.T.), Kobe University, Nada, Kobe 657–8501, Japan; Cryobiosystem Research Center, Faculty of Agriculture, Iwate University, Morioka, Iwate 020–8550, Japan (K.S., A.R.); and Radiation-Applied Biology Division, Japan Atomic Energy Agency, Takasaki, Gunma 370–1292, Japan (Y. Oono)

We investigated the role of ethylene and auxin in regulating the growth and morphology of roots during mechanical impedance by developing a new growing system and using the model plant Arabidopsis (Arabidopsis thaliana). The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Abidur Rahman (abidur{at}iwate-u.ac.jp).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.115519

^* Corresponding author; e-mail abidur{at}iwate-u.ac.jp.

Received December 26, 2007; accepted February 12, 2008; published February 20, 2008.

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On the Inside

Peter V. Minorsky
Plant Physiol. 2008 146: 1455-1456. [Full Text]