Point Mutations in the Coat Protein Gene of Tobacco Mosaic Virus Induce Hypersensitivity in Nicotiana sylvestris. James N. Culver. Department of Plant Pathology, University of California, Riverside 92521 U.S.A. William O. Dawson. Department of Plant Pathology, University of California, Riverside 92521 U.S.A. MPMI 2:209-213. Accepted 5 April 1989. Copyright 1989 The American Phytopathological Society.

Four point mutations in different regions of the coat protein gene of tobacco mosaic virus (TMV) were created by site-directed mutagenesis. Mutations were made at nucleotide 5745 (guanine to adenine), 5773 (cytosine to uracil), 5788 (adenine to guanine), and 5850 (adenine to guanine) to alter single amino acids in the coat protein at position 11 (Val to Met), 20 (Pro to Leu), 25 (Asn to Ser), and 46 (Arg to Gly), respectively. Infectious transcripts of the four mutagenized cDNA clones produced phenotypically distinct hypersensitive reactions on Nicotiana sylvestris (N’ genotype) and systemic responses on N. tabacum ‘Xanthi’ (n genotype). The parental wild-type virus produced systemic mosaic symptoms on both hosts. Sequence data from virion RNA as well as maintenance of phenotype showed that the introduced mutations were stable. This work demonstrates that a number of sites in the coat protein gene of TMV affect host response.