Increased ribonuclease activity in Solanum tuberosum L. transformed with heterologous genes of apoplastic ribonucleases as a putative approach for production of virus resistant plants.

Viral pathogens seriously decrease the yield of potato (Solanum tuberosum L.) -an important agricultural crop. Therefore, there is a demand for potato cultivars resistant to multiple viruses. Ribonucleases (RNases) are supposed to be engaged to antiviral response in plants. Heterologous RNase gene expression provides a tool for production of cultivars with multiple resistance to viruses and viroids. Transgenic potato cultivars Luhivs'ka and Lasynak with heterologous genes bov and ZRNase II of apoplastic RNases from Bos taurus and Zinniaelegans respectively were obtained via Agrobacterium-mediated transformation. The presence of bov and ZRNase II transgenes was confirmed by PCR analysis. RNase activity was examined by modified Oleshko method. Plants with heterologous ribonuclease genes had higher level of RNase activity compared to nontransgenic ones. Transgenic plants inoculated with Potato virus Y, PVY (genus Potyvirus, family Potyviridae) demonstrated delayed and less severe symptoms of viral infection. DAS-ELISA confirmed the presence of viral antigens both in transformed and control plants. Visual manifestations of viral infection in transgenic potatoes were milder than in control plants and their development was delayed, but complete elimination of the virus did not occur.