Studies of coat protein-mediated resistance to TMV. I. The PM2 assembly defective mutant confers resistance to TMV.
Tobacco mosaic virus mutant PM2 contains two amino acid changes in coat protein sequence relative to the sequence of the coat protein of TMV U1. This results in unstable infectivity, inability to cause normal systemic infection, and accumulation of elongated open helixes of coat protein. Using site-directed mutagenesis we demonstrated that the characteristics of PM2 are due to the change of Thr28-->Ile, while the second change, Glu95-->Asp, had no apparent effect on virion structure or infectivity. Transgenic Nicotiana tabacum cv Xanthi NN and Xanthi nn plants that accumulate coat protein that contains one or both of the amino acid changes are as resistant to TMV infection as transgenic plants that contain wild-type TMV coat protein. The implication of these results on a model for coat protein-mediated resistance that involves the interaction of transgenic coat protein with the challenge virus is discussed.
Clark
W G
WG
Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
Fitchen
J H
JH
Beachy
R N
RN
D000596:Amino Acids; D001483:Base Sequence; D002213:Capsid / Q000737:chemistry / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018515:Plant Leaves / Q000821:virology; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011487:Protein Conformation; D014026:Nicotiana / Q000821:virology; D014027:Tobacco Mosaic Virus / Q000235:genetics / Q000472:pathogenicity*; D015678:Viral Structural Proteins / Q000235:genetics*; D014771:Virion / Q000235:genetics / Q000648:ultrastructure
D000596:Amino Acids; D015678:Viral Structural Proteins