Viruses that infect plants invade cells in methods that are distinct from those used by viruses that infect animals. Plant viruses need to attach to the cell wall, and then punch holes in it before they can fuse with the cell membrane and release their genetic material. This is a very costly invasion in terms of energy. Tobacco mosaic virus and wheat mosaic virus both have evolved coat proteins. The proteins that make up the coat of the wheat mosaic virus are tightly wound around each other like bit-helixes, and the viral RNA is in between the folds.