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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

The MYB96 Transcription Factor Mediates Abscisic Acid Signaling during Drought Stress Response in Arabidopsis^1,[W]

Molecular Signaling Laboratory, Department of Chemistry (P.J.S., S.-G.K., C.-M.P.), Department of Agricultural Biotechnology and Center for Fungal Pathogenesis (J.-Y.P., Y.-H.L.), and Plant Genomics and Breeding Institute (C.-M.P.), Seoul National University, Seoul, Korea 151–742; Key Laboratory of Plant Cell Engineering and Germplasm Innovation, School of Life Sciences, Shandong University, Jinan 250100, Shandong, China (F.X., M.Q.); and Department of Molecular Biology, Brain Korea 21 Graduate Program for RNA Biology, Institute of Nanosensor and Biotechnology, Dankook University, Yongin, Korea 448–701 (Y.N.L., W.J.P.)

Plant adaptive responses to drought are coordinated by adjusting growth and developmental processes as well as molecular and cellular activities. The root system is the primary site that perceives drought stress signals, and its development is profoundly affected by soil water content. Various growth hormones, particularly abscisic acid (ABA) and auxin, play a critical role in root growth under drought through complex signaling networks. Here, we report that a R2R3-type MYB transcription factor, MYB96, regulates drought stress response by integrating ABA and auxin signals. The MYB96-mediated ABA signals are integrated into an auxin signaling pathway that involves a subset of GH3 genes encoding auxin-conjugating enzymes. A MYB96-overexpressing Arabidopsis (Arabidopsis thaliana) mutant exhibited enhanced drought resistance with reduced lateral roots. In the mutant, while lateral root primordia were normally developed, meristem activation and lateral root elongation were suppressed. In contrast, a T-DNA insertional knockout mutant was more susceptible to drought. Auxin also induces MYB96 primarily in the roots, which in turn induces the GH3 genes and modulates endogenous auxin levels during lateral root development. We propose that MYB96 is a molecular link that mediates ABA-auxin cross talk in drought stress response and lateral root growth, providing an adaptive strategy under drought stress conditions.

² These authors contributed equally to the article.

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: Chung-Mo Park (cmpark{at}snu.ac.kr).

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

www.plantphysiol.org/cgi/doi/10.1104/pp.109.144220

^* Corresponding author; e-mail cmpark{at}snu.ac.kr.

Received July 2, 2009; accepted July 17, 2009; published July 22, 2009.