FIG. 3.

Schematic illustration of the Bromoviridae life cycle in a protoplast cell. The viral entry (a) to the protoplast cell can be supported via polyethylene glycol or electroporation-mediated changes in membrane permeability. Following uncoating (b) and early translation (c) of viral replication proteins, the induction of spherule formation (d), where viral RNA replication (e) occurs, has been observed (6). Newly synthesized mRNAs egress into the cytoplasm for sgRNA transcription (f) and translation of other viral products, such as MP and CP, that are engaged in virion maturation (g). The presence of viral MP triggers the formation of tubular structures that mediate virion cell-to-cell transfer via a tubule-guided mechanism (99, 109, 134). ER, endoplasmic reticulum.