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Identifier 000434205
Title Ετερόλογη έκφραση της VIRP1 και μελέτη της ομόλογης της, GTE7, στο φυτό Arabidopsis thaliana
Alternative Title Heterologous expression of VIRP1 and study of its homolog, GTE7, in Arabidopsis thaliana
Author Φρουδάκη, Μυρσίνη Α.
Thesis advisor Καλαντίδης, Κρίτων
Reviewer Μόσχου, Παναγιώτης
Τσαγρή, Ευθυμία
Abstract Viroids constitute a special type of pathogens limited to infecting land plants. They are small, circular, monoclonal RNAs, that don’t code for any protein and therefore are completely dependent on host factors. Viroids are capable of promoting their own binding to endogenous factors, and the inability of a viroid to bind to one such factor suffices for the disruption of its biological cycle and the induction of plant resistance to it. VIRP1 (Viroid-RNA Binding Protein 1) is a highly conserved protein of the Solanaceae species with a major role in the biological cycle of Pospiviroids in those plant species. It exhibits the two characteristic domains of the BET protein family of transcription regulators, namely a bromodomain and a NET (N-Extra-Terminal) domain, plus it has a nuclear localisation. Both its endogenous role and the exact nature of its involvement in the biological cycle of Pospiviroid remain elusive. However, there is evidence supporting the involvement of VIRP1 in viroid transfer, probably at the subcellular, or even the subnuclear level. Viroid binding to VIRP1 engages two structural features: the distinctive RY motif, present in all nuclear viroids (Pospiviroidae family) and an atypical RNA binding domain (RNA-BD) found in VIRP1. Σhis domain appears to be conserved in VIRP1 homologs found in host species of Pospiviroidae. To the contrary, in the case of GTE7, the closest homolog to VIRP1 in Arabidopsis thaliana, sequence conservation remains high for the bromo and NET domains, while being greatly reduced in the region corresponding to the RNA BD. Concurrently, A.thaliana is fully resistant to viroids, despite having all the enzymatic background to support the propagation of viroids in the nucleus. In the context of the present thesis, transgenic Arabidopsis Virp1 plants, overexpressing the VIRP1 protein of tomato (Lycopersicon esculentum), were created. These plants are to be used in experiments involving their infection by viroids of Pospiviroid genus, in order to examine whether the heterologous expression of VIRP1 is capable of permitting the infection of Arabidopsis. Also, the proteins AtGTE7, LeVIRP1 and LeVIRP1Δ (lacking the RNA- binding domain) were cloned in translational fusion with the protein epitope FLAG, as to investigate, through immunoprecipitation, if GTE7 has conserved the binding capacity of its homolog, VIRP1, towards viroids. Taken together, these two experimental setups aim to clarify if the etiological agent of Arabidopsis resistance to Pospiviroid is the incapability of viroids to bind to GTE7, which represents the closest endogenous homolog to VIRP1 in Arabidopsis species. Additionally, the construction of transgenic Arabidopsis Virp1, provides a handy heterologous system for the study of the intrinsic role of VIRP1. Finally, if these transgenic plants are proven to serve as hosts for the Pospiviroid species, the present thesis will have contributed to the establishment of an advantageous biological platform for the study of those viroids, and possibly for the study of the whole Pospiviroidae family.
Language Greek
Subject BET family of transcriptional regulations
Binding of viroids
Pospiviroidae
Οικογένεια μεταγραφικών ρυθμιστών BET
Πρόσδεση ιοειδών
Issue date 2020-11-27
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/d/9/0/metadata-dlib-1606292962-749785-2769.tkl Bookmark and Share
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