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Use of a Tobacco mosaic virus-based vector for the identification of 16SrIII-J phytoplasma effector proteins

Alan Zamorano: University of Chile

<div>16SrIII-J phytoplasma is a pathogenic bacteria with an extensive distribution in Chile and South America, and it is associated to several diseases in woody and herbaceous hosts. Regarding the importance of these phytoplasma, it is necessary to understand the mechanisms of pathogenicity involved in the symptom induction. Many phytoplasma belonging to different ribosomal groups, are able to induce symptoms in plants by a single protein that interferes in gene expression. Thus, in this work we propose to determine the impact of the transient expression of two potential 16SrIII-J phytoplasma effectors, orthologs to SAP54 and SAP05, using a viral vector based in a hypovirulent strain of TMV (pBSG-1057). After vector construction by sticky-end ligation and T7 polymerase <em>in vitro</em> transcription, 10 plants of <em>Nicotiana benthamiana</em> and <em>Arabidopsis thaliana</em> ecotype Shahdara were inoculated with viral RNA using bentonite protocol. Phytoplasma genes were detected in non-inoculated leaves 7 days post-inoculation. 4 weeks post-inoculation, plants exhibited symptoms of leafy-flower and leaf alterations in SAP54-like and SAP05-like inoculations, respectively. No symptoms were observed in TMV-GFP inoculated plants. This is the first identification of effector proteins in a phytoplasma belonging to 16SrIII ribosomal group. This work also represents the initial step for the understanding of the mechanisms underlying the pathogenicity and polyphagia associated 16SrIII-J phytoplasma</div>