This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 19/11/3805    most recent tpc.106.048900v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zhao, J. Articles by Guo, Y. Search for Related Content PubMed PubMed Citation Articles by Zhao, J. Articles by Guo, Y. Agricola Articles by Zhao, J. Articles by Guo, Y.

SAD2, an Importin β-Like Protein, Is Required for UV-B Response in Arabidopsis by Mediating MYB4 Nuclear Trafficking^[W]

^a State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100094, China
^b National Institute of Biological Sciences, Beijing, Zhongguancun Life Science Park, Beijing 102206, China
^c Department of Biology, Liaocheng University, Shandong Province, 252059, China
^d Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721

¹ Address correspondence to guoyan{at}nibs.ac.cn.

We report that the Arabidopsis thaliana mutant sensitive to ABA and drought2 (sad2), which harbors a T-DNA insertion in an importin β-like gene, is more tolerant to UV-B radiation than the wild type. Analysis of cyclobutane pyrimidine dimer accumulation revealed that less DNA damage occurred in sad2 than in the wild type during UV-B treatment. No significant growth difference was observed between sad2 and the wild type when treated with the genotoxic drug methyl methanesulfonate, suggesting that SAD2 functions in UV-B protection rather than in DNA damage repair. Whereas the R2R3-type transcription repressor MYB4 has previously been shown to negatively regulate the transcription of cinnamate 4-hydroxylase (C4H) and thus to regulate the synthesis of sinapate esters, expression of both MYB4 and C4H and accumulation of UV-absorbing compounds were significantly higher in sad2 than in the wild type. MYB4 did not localize to the nucleus in the sad2 mutant, suggesting that SAD2 is required for MYB4 nuclear trafficking. SAD2 and MYB4 coimmunoprecipitated, indicating that these proteins localize in the same complex in vivo. MYB4 protein specifically bound to its own promoter in gel shift assays and repressed its own expression, demonstrating that MYB4 protein and mRNA are part of a negative autoregulatory loop. This feedback loop is altered in the sad2 mutant due to the absence of MYB4 protein in the nucleus, leading to the constitutive expression of MYB4 and C4H and resulting in accumulation of UV-absorbing pigments that shield the plant from UV-B radiation.

This article has been cited by other articles:

				Y. Lee, H.-S. Lee, J.-S. Lee, S.-K. Kim, and S.-H. Kim Hormone- and light-regulated nucleocytoplasmic transport in plants: current status J. Exp. Bot., September 1, 2008; 59(12): 3229 - 3245. [Abstract] [Full Text] [PDF]

				S. Mintz-Oron, T. Mandel, I. Rogachev, L. Feldberg, O. Lotan, M. Yativ, Z. Wang, R. Jetter, I. Venger, A. Adato, et al. Gene Expression and Metabolism in Tomato Fruit Surface Tissues Plant Physiology, June 1, 2008; 147(2): 823 - 851. [Abstract] [Full Text] [PDF]