Improved silencing suppression and enhanced heterologous protein expression are achieved using an engineered viral helper component proteinase.

Highlights: [•] RNA silencing limits transient expression of heterologous proteins in plants. [•] Co-expressed viral silencing suppressors can enhance heterologous protein yields. [•] Mutations in HCpro protein made it more efficient in silencing suppression. [•] Enhanced silencing suppression by mutated HCpro caused no harm to plant tissues. [•] Mutated HCpro proteins were superior enhancers of heterologous protein expression. [ABSTRACT FROM AUTHOR]