REN and viral infectious disease: This feature of MCLV-encoded V2 strongly enhancing viral genome replication during viral infection is similar to that reported for begomovirus- and curtovirus-encoded C3/AC3, where the C3 protein enhances viral replication and gene expression in N. benthamiana and is a replication enhancer (REn) protein required for the efficient proliferation of viral DNA [15,19,35].