Heterologous RNA silencing suppressors from both plant- and animal-infecting viruses support Plum pox virus infection

Abstract

[EN] HCPro, the RNA silencing suppressor (RSS) of viruses belonging to the Potyvirus genus in the Potyviridae family, is a multifunctional protein presumably involved in all essential steps of the viral infection cycle. Recent studies have shown that Plum pox potyvirus (PPV) HCPro can be successfully replaced by Cucumber vein yellowing ipomovirus P1b, a sequence unrelated RSS from a virus of the same family. In order to gain insight into the requirement of a particular RSS to establish a successful potyviral infection, we tested the ability of different heterologous RSSs from both plant- and animal-infecting viruses to substitute HCPro. Making use of engineered PPV chimeras, we show that PPV HCPro can be functionally replaced by some, but not all, unrelated RSSs, including the NS1 protein of the mammalian-infecting Influenza A virus. Interestingly, the capacity of a particular RSS to replace HCPro does not strictly correlate with its RNA silencing suppression strength. Altogether, our results suggest that not all suppression strategies are equally suitable for an efficient escape of PPV from the RNA silencing machinery. The approach followed here based on using PPV chimeras in which an under-consideration RSS substitutes for HCPro could further help to study the function of diverse RSSs in a ¿highly-sensitive¿ RNA silencing context, such as that taking place in plant cells during the process of a viral infection.