Intracellular membranes are critical for replication of positive-strand RNA viruses. To dissect the roles of various lipids, we have developed an artificial phosphatidylethanolamine (PE) vesicle-based Tomato bushy stunt virus (TBSV) replication assay. We demonstrate that the in vitro assembled viral replicase complexes (VRCs) in artificial PE vesicles can support a complete cycle of replication and asymmetrical RNA synthesis, which is a hallmark of (+)-strand RNA viruses. Vesicles containing ∼85% PE and ∼15% additional phospholipids are the most efficient, suggesting that TBSV replicates within membrane microdomains enriched for PE. Accordingly, lipidomics analyses show increased PE levels in yeast surrogate host and plant leaves replicating TBSV. In addition, efficient redistribution of PE leads to enrichment of PE at viral replication sites. Expression of the tombusvirus p33 replication protein in the absence of other viral compounds is sufficient to promote intracellular redistribution of PE. Increased PE level due to deletion of PE methyltransferase in yeast enhances replication of TBSV and other viruses, suggesting that abundant PE in subcellular membranes has a proviral function. In summary, various (+)RNA viruses might subvert PE to build membrane-bound VRCs for robust replication in PE-enriched membrane microdomains.
Keywords: host factor; phospholipid; plant virus; viral replicase complex; virus–host interaction.