Athanasios Dalakouras

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So far, conventional hairpin RNA (hpRNA) constructs consisting of an inverted repeat (IR) of target promoters directly introduced into an expression cassette have been used to mediate de novo DNA methylation. Transcripts of such constructs resemble mRNA molecules, and are likely to be exported to the cytoplasm. The presence of hpRNAs in the cytoplasm and(More)
RNA-directed DNA methylation (RdDM) involves sequence-specific guiding of the de novo methylation machinery to complementary genomic DNA by RNA molecules. It is still elusive whether guide RNAs bind directly to DNA or to nascent transcripts produced from it. Even the nature of the guide RNAs is not elucidated. RNA interference (RNAi) studies provided a link(More)
In plants, RNA-directed DNA methylation (RdDM) can target both transgene promoters and coding regions/gene bodies. RdDM leads to methylation of cytosines in all sequence contexts: CG, CHG and CHH. Upon segregation of the RdDM trigger, at least CG methylation can be maintained at promoter regions in the progeny. So far, it is not clear whether coding region(More)
In plants, transgenes frequently become spontaneously silenced for unknown reasons. Typically, transgene silencing involves the generation of small interfering RNAs (siRNAs) that directly or indirectly target cognate DNA and mRNA sequences for methylation and degradation, respectively. In this report, we compared spontaneous silencing of a transgene in(More)
In plants, transgenes containing Potato spindle tuber viroid (PSTVd) cDNA sequences were efficient targets of PSTVd infection-mediated RNA-directed DNA methylation. Here, we demonstrate that in PSTVd-infected tobacco plants, a 134 bp PSTVd fragment (PSTVd-134) did not become densely methylated when it was inserted into a chimeric Satellite tobacco mosaic(More)
In plants, transgenes are generally more sensitive against RNA silencing than endogenes are. In this study, we generated a transgene that structurally mimicks an endogene. It is composed of endogenous promoter, 5'-UTR, introns, 3'-UTR and terminator elements. Our data revealed that, in contrast to a conventional transgene, an endogene-resembling transgene(More)
Previously, we had shown that stable expression of a hairpin RNA sharing homology with the coat protein (CP) of the Cucumber mosaic virus (CMV) (hpRNA(CMV)) produced CMV resistant Nicotiana tabacum plants. However, only 17% of the hpRNA(CMV)-expressing plants generated substantial amounts of siRNAs that mediated CMV resistance (siRNAs(CMV)). Here, we(More)
In plants, endogenes are less prone to RNA silencing than transgenes. While both can be efficiently targeted by small RNAs for post-transcriptional gene silencing (PTGS), generally only transgene PTGS is accompanied by transitivity, RNA-directed DNA methylation (RdDM) and systemic silencing. In order to investigate whether a transgene could mimick an(More)
RNA-directed DNA methylation (RdDM) in plants has been extensively studied, but the RNA molecules guiding the RdDM machinery to their targets are still to be characterized. It is unclear whether these molecules require full complementarity with their target. In this study, we have generated Nicotiana tabacum (Nt) plants carrying an infectious tomato apical(More)
In South Asia, Cotton leaf curl disease (CLCuD) is caused by a complex of phylogenetically-related begomovirus species and a specific betasatellite, Cotton leaf curl Multan betasatellite (CLCuMuB). The post-transcriptional gene silencing (PTGS) suppression activities of the transcriptional activator protein (TrAP), C4, V2 and βC1 proteins encoded by Cotton(More)