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The ubiquitin–proteasome system is a highly conserved machinery that plays a crucial role in plant defense against viruses. However, the number of E3 ligases targeting viral proteins remains limited. Although RING‐between‐RING (RBR)‐type E3 ligases are evolutionarily conserved across organisms, their functions in plant responses to biotic stress remain largely unknown. Herein, it is found that the triple gene block 1 (TGB1) protein of the barley stripe mosaic virus (BSMV) undergoes ubiquitination during viral infection. Immunoprecipitation combined with mass spectrometry identified an RBR‐type E3 ligase that interacted with TGB1 in vivo and in vitro. The overexpression of Ariadne‐like protein 8 (ARI8) inhibits, whereas its knockout enhances, the local and systemic spread of BSMV. ARI8 mediated the ubiquitination of TGB1, and its Cys311 residue is required for the ARI8‐mediated degradation of TGB1 and inhibition of BSMV infection. In addition to BSMV, ARI8 negatively regulates infection by other TGB‐containing viruses, including potato virus X and beet necrotic yellow vein virus. Collectively, the findings identified a new E3 ligase that targets a plant viral protein and reveals a previously uncharacterized role for RBR‐type E3 ligases in plant responses to biotic stress, providing a potential molecular target for the development of antiviral strategies in plants. The plant RING‐between‐RING (RBR)‐type E3 ligase, Ariadne‐like protein 8 (ARI8), ubiquitinates and degrades a viral movement protein, restricting virus spread. ARI8 also inhibits other triple gene block 1 (TGB1)‐containing viruses, revealing a broad‐spectrum antiviral role. This study uncovers a previously unknown function of RBR‐type E3 ligases in plant immunity and offers a potential target for antiviral crop improvement.

The aim of this short review was to summarize recent advances in the field of viral cell-to-cell movement mediated by the triple gene block (TGB). The growing body of new research has uncovered links between virus cell-to-cell trafficking and replication, silencing suppression, virus spread over the plant, as well as suggested the roles of nucleus/nucleolus in plant virus transport and revealed protein-membrane associations occurring during subcellular targeting and cell-to-cell movement. In this context, our review briefly summarized current views on several potentially important functions of TGB proteins and on the development of new experimental systems that improved understanding of the molecular events during TGB-mediated virus movement.