한빛사 논문
Abstract
Moon Young Ryu, Seok Keun Cho, and Woo Taek Kim*
Department of Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120.749, Korea
1 This work was supported by grants from the National Research Foundation (project no. 2009.0078317 funded by the Ministry of Education, Science, and Technology, Republic of Korea), the Technology Development Program for Agriculture and Forestry (project no. 309017.5 funded by the Ministry for Agriculture, Forestry, and Fisheries, Republic of Korea), and the BioGreen 21 Program (funded by the Rural Development Administration, Republic of Korea) to
W.T.K.
* Corresponding author
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: Woo Taek Kim.
[C] Some figures in this article are displayed in color online but in black and white in the print edition.
[W] The online version of this article contains Web-only data.
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Ubiquitination is a eukaryotic posttranslational protein modification that is mediated by the cascade of E1, E2, and E3 ubiquitin (Ub) ligases and is involved in regulating numerous cellular functions. In this study, we obtained 100 different Arabidopsis (Arabidopsis thaliana) T-DNA insertion mutant plants in which RING E3 Ub ligase genes were suppressed and monitored their phenotypes in the presence of exogenous abscisic acid (ABA), a plant stress hormone. One of these loss-of-function mutants displayed ABA-insensitive phenotypes at the germination stage and was named atairp1 (for Arabidopsis ABA-insensitive RING protein 1). AtAIRP1 encodes a cytosolic protein containing a single C3H2C3-type RING motif with in vitro E3 Ub ligase activity. AtAIRP1 was significantly induced by ABA and drought stress. In contrast to atairp1 mutant plants, AtAIRP1- overexpressing transgenic plants (35S:AtAIRP1-sGFP) were hypersensitive to exogenous ABA in terms of radicle emergence, cotyledon development, root elongation, and stomatal closure. Ectopic expression of AtAIRP1-sGFP in atairp1 effectively rescued the loss-of-function ABA-insensitive phenotype. Both 35S:AtAIRP1-sGFP and atairp1/35S:AtAIRP1-sGFP plants accumulated higher amounts of hydrogen peroxide in response to exogenous ABA than did wild-type and atairp1 mutant plants. AtAIRP1 overexpressors were markedly tolerant to severe drought stress, as opposed to atairp1, which was highly susceptible. The levels of drought stress-related genes and basic leucine zipper transcription factor genes were up-regulated in the 35S:AtAIRP1-sGFP lines relative to wild-type and atairp1 mutant plants in response to ABA. Overall, these results suggest that AtAIRP1, a C3H2C3-type RING E3 Ub ligase, is a positive regulator in the Arabidopsis ABA-dependent drought response.
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