Epigenetic regulation of endogenous plant pararetroviruses

摘要: This thesis focuses on epigenetic processes involved in the regulation of gene expression endogenous pararetroviruses (EPRVs), exemplified by Petunia vein clearing virus (ePVCV-1) and its episomal form, PVCV. Since ePVCV-1/PVCV was found to have features characteristic retrotransposon retroviruses (Richert-Poggeler Shepherd, 1997), detailed analysis these retroelements different systems gives a deep insight understand interconnection elements their host cellular machinery as described chapter one. Chapter two describes silencing states ePVCV-1 distinct hybrida lines, “white 138” (W138) “rose du ciel” (Rdc). Despite integration into pericentromeric regions chromatin, we that this position still allows for low level transcription increases with increasing plant age is higher W138 than Rdc. To correlate findings marks, compared cultivars respect DNA- histone-methylation siRNA production. Using bisulfite treatment, sequences were be methylated at cytosines all contexts. Astonishingly, however, both hosts methylation rate non-coding region containing promoter relatively low. might indicate special ability viral escape complete inactivation methylation. In Rdc, nearly histones covering coding lysine 9 histone 3 (H3K9), flag heterochromatin, while about half them H3K9- H3K4-type, latter representing active chromatin. Interestingly accordance DNA data, H3K4/H3K9 ratio high cultivars. The correlates an increased induction. Furthermore, show production siRNAs three size classes (24, 22 21 nt) cultivars, of which are weaker Together our observations less efficient Rdc. In three, I investigated PVCV determined direct transgenic plants. analyzed regulatory particular comparison those other pararetrovirus promoters. studied functionality as-1 like element contribution expression. Although originally medium strength, could improved 50% strength CaMV 35S “repairing“ pair degenerated enhancer elements. We show, includes upstream downstream elements, it can considerably restoring elements. The concept creating virus-resistant plants transformation genes derived from pathogen genome well-exploited highly effective procedure fight viruses causal agents diseases (Fichen Beachy, 1993). Recently has been demonstrated RNA interference (RNAi) successfully triggered against transient inverted repeat target (Pooggin et al., 2003; Tenllado 2004). four, use technique develop RNA-mediated banana streak resistance via TGS and/or PTGS method should prevent outbreak infection upon rare spontaneous induction BSV tissue culture. Chapter five publication EMBO journal which contributed major ways. paper cloned originating directly library. Our allowed comparative horizontally vertically transmitted forms infectivity using biolistic provirus-free petunia species. Some integrants within P.hybrida arranged tandem, allowing release transcription. addition known inducers pararetroviruses, such hybridization, culture abiotic stresses, observed activation after wounding. data also support hypothesis uses control pararetrovirus. In preamble point out, part based my own experimentation interpretation.