Antagonistic within‐host interactions between plant viruses: molecular basis and impact on viral and host fitness

Abstract

Double infections of related or unrelated viruses frequently occur in single plants, the viral agents being inoculated into the host plant simultaneously (co-infection) or sequentially (super-infection). Plants attacked by viruses activate sophisticated defence pathways which operate at different levels, often at significant fitness costs, resulting in yield reduction in crop plants. The occurrence and severity of the negative effects depend on the type of within-host interaction between the infecting viruses. Unrelated viruses generally interact with each other in a synergistic manner, whereas interactions between related viruses are mostly antagonistic. These can incur substantial fitness costs to one or both of the competitors. A relatively well-known antagonistic interaction is cross-protection, also referred to as super-infection exclusion. This type of interaction occurs when a previous infection with one virus prevents or interferes with subsequent infection by a homologous second virus. The current knowledge on why and how one virus variant excludes or restricts another is scant. Super-infection exclusion between viruses has predominantly been attributed to the induction of RNA silencing, which is a major antiviral defence mechanism in plants. There are, however, presumptions that various mechanisms are involved in this phenomenon. This review outlines the current state of knowledge concerning the molecular mechanisms behind antagonistic interactions between plant viruses. Harmful or beneficial effects of these interactions on viral and host plant fitness are also characterized. Moreover, the review briefly outlines the past and present attempts to utilize antagonistic interactions among viruses to protect crop plants against destructive diseases.

The Coat Protein and NIa Protease of Two Potyviridae Family Members Independently Confer Superinfection Exclusion

“…However, virusvirus interactions in hosts that facilitate superinfection exclusion (SIE) between related viruses or synergistic interactions between unrelated viruses have received less attention (4,5). Synergistic interactions are facilitative virus-virus interactions between two or more unrelated viruses, and these interactions often cause increased virus accumulation of one or both viruses that could lead to severe disease compared to infection by individual viruses (4).…”

A Framework for the Evaluation of Biosecurity, Commercial, Regulatory, and Scientific Impacts of Plant Viruses and Viroids Identified by NGS Technologies

“…The biological characterization of new viruses may be particularly challenging with complex of different viruses, where the combination of two or more viruses can significantly modify their pathogenic potential through synergistic or antagonistic interactions (Martin and Elena, 2009; Syller and Grupa, 2016). Mixture of virus species is indeed very frequent, especially in woody plants like grapevine (Jooste et al, 2015), often leading to unpredictable variations in symptoms, infectivity, accumulation, and/or vector transmissibility.…”

Grapevine–virus–environment interactions: an intriguing puzzle to solve

“…Vegetative propagation, use of infected rootstocks and vector transmission can contribute to multiple infection events in vineyards. In these situations, some eventual relationships established among different viruses could result in synergistic or antagonistic (competitive) interactions (Syller & Grupa, ). (4) Human selection.…”