Insights Into Virus-Encoded RNA Silencing Suppressors Across Viral Families: A Focus on Viruses Infecting Solanaceae Crops.

Viral suppressors of RNA silencing (VSRs) are proteins that interfere with antiviral defense mechanisms and enhance infection. For plant viruses, VSRs can be encoded in viral genomes and satellite molecules and play an important role in the virus's life cycle and in overcoming host defenses. However, a comprehensive review on the multifunctionality of VSRs and their role in the worldwide spread of plant viral diseases has not been performed. Here, we aim to synthesize the current understanding of the role of VSRs in the pathogenesis of Solanaceous plants, a family that includes many crops and medicinal plants. We focus on three key areas: (1) the diversity of VSRs and the mechanisms used to suppress antiviral defense, (2) the role of VSRs in viral pathogenesis beyond interfering with host RNA-silencing, and (3) the coevolution between VSRs and plant host proteins. Additionally, we describe how VSRs promote the development of diseases by altering various steps in viral pathogenicity via induction of counter-defense mechanisms. Specifically, a substantial body of evidence suggests that VSRs induce the suppression of antiviral silencing, abrogation of phytohormone signaling, and downregulation of R-gene-mediated host defense. Furthermore, we discuss how identifying and characterizing novel interactions between VSRs and Solanaceous host factors may be leveraged for developing sustainable pathogen and pest management strategies.