FIG. 9.

Effects of cleavage site mutations on viral infectivity. (A) Schematic representation of the infectious TYMV in vitro transcript E17 and its derivatives. Residue Cys783 is indicated by an open circle or by a filled circle when mutated to Ser. The PRO/HEL and HEL/POL cleavage sequences are represented by filled and open triangles, respectively. Deletions are indicated by broken lines and introduced stop codons by asterisks. ×, alanine substitutions resulting in impaired cleavage. (B) Arabidopsis protoplasts were transfected with wild-type or mutant in vitro transcripts, alone or in combination with expression vectors as indicated. The cells were harvested 48 h posttransfection, and the abilities of the transcripts to replicate were assessed by immunoblot analysis of equivalent amounts of proteins using anti-CP antibodies. The relative accumulation of CP is indicated below each panel.