Abstract: A single vector or multiple separate vectors that contain two or more non-competing replicons for transient expression of the heavy and light chains of Rituximab in Nicotiana benthamiana leaves is described. The correct assembly of these subunit proteins into functional oligomeric structures to optimize the expression is also described. This system advances plant transient expression technology by eliminating the need for non-competing viruses, and thus, enhances the realistic commercial application of the multi-replicon single vector system for producing Rituximab in plant cells.