Complex sentence: Some viruses have developed proteins called Silencing Suppressors in response to RNAi, the mechanism is unknown, but mutation in those proteins allow the plant to recover from viral infection and prevents systemic infections.
Split into simpler sentences: Some viruses have developed proteins called Silencing Suppressors in response to RNAi. The mechanism is unknown, but mutation in those proteins allow the plant to recover from the viral infection and prevents systemic infections.