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SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION

Down-Regulation of a SILENT INFORMATION REGULATOR2-Related Histone Deacetylase Gene, OsSRT1, Induces DNA Fragmentation and Cell Death in Rice^1,[C],[W]

National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China (L.H., Q.S., F.Q., C.L., Y.Z.); Department of Quartermaster, Military Economy Academy, Wuhan 430035, China (L.H.); and Institut de Biotechnologie des Plantes, Université Paris Sud 11, 91405 Orsay, France (D.-X.Z.)

The SILENT INFORMATION REGULATOR2 (SIR2) family proteins are NAD⁺-dependent histone deacetylases. Sir2 is involved in chromatin silencing at the mating-type loci, rDNA, and telomeres in yeast and is associated with lifespan extension in yeast, worms, and flies, but also in a broader range of additional functions. In this work, we investigated the role of OsSRT1, one of the two SIR2-related genes found in rice (Oryza sativa). We show that OsSRT1 is a widely expressed nuclear protein with higher levels in rapidly dividing tissues. OsSRT1 RNA interference induced an increase of histone H3K9 (lysine-9 of H3) acetylation and a decrease of H3K9 dimethylation, leading to H₂O₂ production, DNA fragmentation, cell death, and lesions mimicking plant hypersensitive responses during incompatible interactions with pathogens, whereas overexpression of OsSRT1 enhanced tolerance to oxidative stress. Transcript microarray analysis revealed that the transcription of many transposons and retrotransposons in addition to genes related to hypersensitive response and/or programmed cell death was activated. Chromatin immunoprecipitation assays showed that OsSRT1 down-regulation induced histone H3K9 acetylation on the transposable elements and some of the hypersensitive response-related genes, suggesting that these genes may be among the primary targets of deacetylation regulated by OsSRT1. Our data together suggest that the rice SIR2-like gene is required for safeguard against genome instability and cell damage to ensure plant cell growth, but likely implicates different molecular mechanisms than yeast and animal homologs.

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: Dao-Xiu Zhou (dao-xiu.zhou{at}u-psud.fr).

^[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.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.099473

^* Corresponding author; e-mail dao-xiu.zhou{at}u-psud.fr; fax 33–1–69153424.

Received March 13, 2007; accepted April 17, 2007; published April 27, 2007.

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Plant Physiol. 2007 144: 1235-1236. [Full Text]