• Arabidopsis thaliana
• Caenorhabditis elegans
• crop protection
• micro RNA
• RNA interference
• SID1
• small RNA
• transporter

RNA interference is a biological process in which RNA molecules, generally known as small RNAs, are able to induce suppression of gene expression, by acting transcriptionally or post-transcriptionally in a sequence-specific way. In plants it is involved in defending cells against viruses, transposons, but also in plant signaling and development processes.
This phenomenon could be exploited for agriculture to create green alternative solutions in crop protection, by designing double stranded RNAs (dsRNAs) active to repress vital genes, both of pests and weed. As the uptake of these molecules also occurs through leaves or root surface, one of the open challenges is to overcome physical and chemical barriers by developing efficient delivery and release strategies. In this work different delivery compounds have been evaluated for improving dsRNAs uptake in plants, among them the transfection reagent DOTAP, the cationic dendrimer polylysine and the surfactant Silwet.
In addition to these experiments, the thesis work has been focused on the study of small RNAs movement in plant tissues. To this point, we know that it occurs principally through plasmodesmata in a cell-to-cell movement, and through phloem, over long distances. However, the mechanism underneath the translocation of small RNAs and their selection before phloem access, is still unknown. Differently, in Caenorhabditis elegans and in other invertebrates, specific transporters responsible for RNAi have been discovered. In particular, SID-1 (systemic interference deficiency) covers an important role in dsRNAs import and translocation between cells. So far, no similar orthologous proteins have been identified in plants. In this work, an optimized sequence encoding for SID-1 has been cloned in Arabidopsis plants in order to characterize this protein in a heterologous context. Its subcellular localization in protoplasts and functionality in homozygous plants have been further evaluated by microscopy and feeding experiments.
The potentialities of this study could be sought in the possibility to make plants naturally more able to uptake external dsRNAs. Moreover, analyzing the mutant phenotype of these transgenic plants, could provide insights on a better understanding of small RNAs movement and physiological role in plants.