XVI International Botanical Congess

We have reported the post transcriptional gene silenced lines of Nicotiana benthamiana plants transformed with the coat protein (CP) gene of sweet potato feathery mottle potyvirus1. Among them, line 4.28 showed the high expression of the trasgene in Northern blot. However, a few plants exhibited complete resistance against the recombinant PVX harboring the same sequence of the CP gene, suggesting post transcriptional gene silencing. We investigated the line in more detail. It was found that the activation of gene silencing in 4.28 was delayed compared to those in the other silenced lines. The level of transgene methylation was increased de novo in the course of development. The characters of delayed gene silencing and developmentally increased methylation were inherited to the next generation.