Abstract |
The Cucurbit yellow stunting disorder virus (CYSDV) infects plants of the Cucurbitaceae family, causing large-scale disasters in their cultures. These plants play an important role in the human nutrition and their production significantly contributes to the global agricultural economy. The mechanism of RNA silencing is used for the defense of the plants against viruses. However, the majority of viruses possess suppressors of RNA silencing which enable them to counteract the anti-viral mechanism of the plants. The aim of the present thesis was the functional study of the CYSDV p25 suppressor of RNA silencing, with in vivo and in vitro experimental approaches. For the in vivo approach, transgenic plants were developed that constantly over-expressed the protein. These plants showed chlorotic phenotype and retardation in growth. According to northern analyses, the suppressor CYSDV p25 did not interact with the biogenesis pathway of the endogenous miRNAs: miR159 and miR167. Moreover, the stable over-expression of the CYSDV p25 protein seemed to strongly suppresses the S-PTGS. The in vitro approach included testing the ability of the suppressor CYSDV p25 to bind double stranded RNA molecules. The failure of heterologous expression of the protein in E. coli bacterial cells did not allow the purification of the protein and the completion of the in vitro experiment. The study of the suppressor CYSDV p25 could uncover a new repression mechanism of RNA silencing, due to the lack of conserved domains and homology with other previously studied viruses. The development of CYSDV p25 transgenic plants is the first step that gives the opportunity to conduct experiments for the investigation of the suppressor. Furthermore, transgenic plants could be used as “factories” for heterologous protein production.
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