Replication Organelles of Plant Positive-Strand RNA Viruses: A Boost in Knowledge Following New Imaging Approaches

As obligate intracellular parasites, viruses depend entirely on host cells for propagation, with replication being the central process in establishing their infections. Upon entry into host cells, positive-strand RNA viruses induce rearrangement of the host's cellular membranes, leading to the formation of virus replication organelles (ROs). Advancements in imaging techniques have enabled the determination of three-dimensional structures for several plant viral ROs that are associated with specific organelle membranes and display either spherule- or tubule-shaped structures. Viral replication proteins, along with diversely recruited host factors such as lipids and membrane-shaping proteins, are used to remodel cellular membranes and build ROs. These ROs not only shield viral replication templates and intermediates from host defense mechanisms but also serve as efficient machinery for the synthesis of viral RNAs. Moreover, ROs are intricately connected to other stages of the viral life cycle, often triggering stress responses and redox shifts within the cellular microenvironment, positioning the ROs as central hubs for virus–plant interactions.