CHARGE CHANGES NEAR THE N-TERMINUS OF THE COAT PROTEIN OF 2 POTYVIRUSES AFFECT VIRUS MOVEMENT

Mutants of tobacco vein mottling virus (TVMV) with substitutions of Ly s or Arg for Asp in the DAG motif at position 5 in the coat protein (C P) failed to infect tobacco plants systemically, but replicated and pr oduced virions in protoplasts. Occasional systemic infections occurred when Nicotiana benthamiana or transgenic tobacco plants expressing wi ldtype TVMV CP were inoculated with these mutants, but viral progeny c ontained reversions to negatively or non-charged amino acids at positi on 5 or substitutions of Glu for Lys at position 8. The compensatory n ature of these mutations was demonstrated by recreating one of the mos t common alterations. Tobacco etch virus (TEV) mutants with substituti ons of Lys for Asp in the two DAG motifs near the CP N terminus also f ailed to infect tobacco plants systemically, and in situ histochemical analysis showed limited movement. A certain net charge evidently must be maintained near the CP N terminus for systemic movement to occur.