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Heavy Metal Stress Induced Inheritable Alterations Of Epigenetic Which May Contribute To Plant Enhanced Resistance To Heavy Metal Damage In Rice

Posted on:2010-11-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:X F OuFull Text:PDF
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As a kind of abiotic stress, heavy metal stress may provoke stress response. In this thesis I found that heavy metal stress induced significant growth inhibition in rice, which showed a dose-dependent response, the extent of inhibition increased with increased metal concentrations. Given the inherent property of epigenetic modifications to response to intrinsic as well as external stress, it is conceivable that epigenetic markers like DNA methylation and gene expression may undergo alterations in response to heavy metal stress. In deed I found here that heavy metal stress could induce extensive alteration in both DNA methylation and gene expression in rice plants, revealed by a set of characterized sequences including transposons and cellular genes. I found that several features characterize the alteration: (1) Alterations are predominant CNG hypomethylation events; (2) Progeny analysis indicated demethylated patterns could be inherited to next generation in most plants, leading to more intensive hypomethylation, and subsequent generation could inherit the altered methylation patterns in most progeny plants; (3) Heavy metal stress induced the perturbation of the expression state of these genes encoding for the enzymatic machinery responsible for establishing and maintaining cytosine methylation patterns and/or chromatin structure such as DNA methytransferases, 5-methylcytosine glycosylase and SWI/SNF chromatin remodeller (DDM1), which may be a major cause for the high-incidence of DNA methylation alterations; (4) Alterations in expression occurred in transposons and cellular genes are predominant up-regulations and occasional down-regulations events, and the alteration state could inherit to progenies at variable frequencies. Alteration in expression did not show a general correlation with alterations in methylation, but I found that hypomethylation specifically occurred, and most elements exhibited up-regulated expression upon heavy metal stress, so the changes in DNA methylation may influence the expression level of a number of genes to some extent. Furthermore, I found that progenies of treated plants showed enhanced resistance in a dose-dependent manner, and OsHMAs showed significant up-regulated expression might help to metal efflux and contribute to enhanced resistance to heavy metal in progenies of treated rice plants. I discuss implications of heavy metal stress-induced epigenetic variations with regard to the resistance mechanism to heavy metal of plants and potentiality for mutagenesis in rice breeding.
Keywords/Search Tags:Heavy metal, DNA methylation alteration, Gene expression, Epigenetic inheritance, Rice
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