Silencing , and of Potato Virus (Viroid) Using Artificial microRNA Confers Resistance to PVX, PVY and PSTVd in Transgenic Potato.

Virus infection is the key constraint to potato cultivation worldwide. Especially, coinfection by multiple viruses could exacerbate the yield loss. Transgenic plants expressing artificial microRNAs (amiRNAs) have been shown to confer specific resistance to viruses. In this study, three amiRNAs containing miR159 as a backbone, expressing genes targeting , and of potato virus X (PVX), potato virus Y (PVY) and potato spindle tuber viroid (PSTVd), were constructed. amiR-159, amiR-159 and amiR-159 were cloned into the plant expression vector pCAMBIA1301 with a CaMV35S promoter, producing the p1301-pre-amiR vector. Twenty-three transgenic plants ( cv. 'Youjin') were obtained by -mediated transformation, and ten PCR-positive transplants were chosen for further analysis. Quantitative real-time PCR results indicated that 10 transgenic plants could express amiRNAs successfully. Southern blotting hybridization proved that amiR-159 had integrated into potato genome in transgenic lines. Viral (viroid) challenge assays revealed that these transgenic plants demonstrated resistance against PVX, PVY and PSTVd coinfection simultaneously, whereas the untransformed controls developed severe symptoms. This study demonstrates a novel amiRNA-based mechanism that may have the potential to develop multiple viral resistance strategies in potato.