Introduction of dsRNA-specific ribonuclease pac1 into Impatiens walleriana provides resistance to Tomato spotted wilt virus

The production of several popular impatiens cultivars in Serbia suffers substantial losses due to high incidence of Tomato spotted wilt virus (TSWV) infections. Since TSWV, like majority of plant viruses, has RNA genome and replicates via double-stranded RNA (dsRNA) intermediates, it is a good target for dsRNA-specific endonuclease encoded by pac1 gene from Schizosaccharomyces pombe. In order to introduce resistance to TSWV, Impatiens walleriana, as well as referent species Nicotiana tabacum, were transformed with Agrobacterium tumefaciens C58C1pac1 bearing a binary vector pKT-Lpac1. The transformation and regeneration was successful in both plant species, but the transformation efficiency was higher in tobacco. The obtained pac1-transformed impatiens and tobacco lines were challenged with TSWV by manual inoculation in vitro. I. walleriana clones expressing pac1 were completely resistant to TSWV. Some of the transgenic tobacco lines also showed complete resistance, while others were infected, but with lower frequency, prolonged incubation period and milder symptoms in comparison to untransformed plants. Comparison of morphological parameters including shoot length, number of nodes, leaf length and number of axillary buds per plant between control and transformed lines revealed that pac1 expression does not alter the morphology of the transformants.