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Study of synergistic interaction between two potexviruses, Cactus virus X and Pitaya virus X

Yueh-Min Wu: Department of Plant Pathology and Microbiology, National Taiwan University

<div><em>Cactus virus X</em> (CVX) and <em>Pitaya virus X </em>(PiVX), which belong to the genus <em>Potexvirus</em>, often co-infect pitaya plants in Taiwan. To study the interaction of CVX and PiVX, the infectious clones of two viruses were constructed. Based on our northern blot analyses of protoplast and plant inoculation experiments, CVX and PiVX are beneficial to each other’s RNA accumulation. These results indicated that synergistic interaction may exist between CVX and PiVX. This is the first report of synergistic effect occurring within different species of the genus <em>Potexvirus</em>. Synergistic interactions are mostly described between unrelated viruses and have been proven due to suppression of RNA silencing in the co-infected plant. Therefore, we want to study whether the synergism between potexviruses is related to RNA silencing. By transiently co-expressing GFP in <em>Nicotiana benthamiana</em> line 16c plant, five viral proteins of CVX and PiVX were separately tested for RNA silencing suppression ability. According to our results, triple gene block protein 1 (TGBp1) and coat protein of CVX and PiVX revealed different degrees of silencing suppression ability. It is suggested that both proteins may be involved in the synergistic interaction. However, the influence of each viral gene on the other virus need further <em>in vivo</em> studies. These experimental results will provide information of how the synergistic interaction works between CVX and PiVX <em>in planta</em>.</div>