Tobamoviruses CP Proteins Hijack Light-Induced Protein (NbLIP1) to Promote Viral Replication by Facilitating VRO Formation.

Tobamoviruses establish viral replication organelles (VROs) on the host endoplasmic reticulum (ER) for their replication, a process demanding substantial different types of lipids. However, how viruses efficiently transfer these lipids from other compartments like chloroplasts remains incompletely understood. Fibrillin (FBN) proteins are primarily localised to chloroplasts and are intimately linked with lipid metabolism and stress responses in chloroplasts. Here, we report that NbLIP1, a light-induced FBN1 family protein in Nicotiana benthamiana, directly interacts with the coat protein (CP) of rehmannia mosaic virus (ReMV) and other related tobamoviruses (TMV, YoMV). Upon viral infection, this interaction leads to the relocalisation of NbLIP1 from chloroplasts to ER-proximal viral replication sites. Functional assays demonstrated that overexpression of NbLIP1 significantly enhanced viral replication, viral protein accumulation, and VRO formation, while silencing NbLIP1 had the opposite effects. These findings unveil a novel viral infection mechanism whereby the viral CP hijacks the host lipid transfer protein NbLIP1 and recruits it to viral replication factories to promote viral replication, potentially by modulating lipid supply or the microenvironment remodelling at the replication sites. This study not only elucidates the role of NbLIP1 as a novel pro-viral host factor but also provides new insights into how viruses exploit host resources across cellular compartments, suggesting NbLIP1 as a potential antiviral target.