Identification of a basic pathogenesis-related, thaumatin-like protein of virus-infected tobacco as osmotin

Abstract

A basic PR protein was isolated and characterized from Samsun NN tobacco leaves infected with tobacco mosaic virus. The protein is serologically-related to the pathogenesis-related (PR) proteins R and S, the thaumatin-like (TL) proteins so-called because of their high level of homology with thaumatin, a sweet-tasting protein from the West African shrub Thaumatococcus daniellii Benth. Its amino acid composition and its NH 2 -terminal sequence indicate that this PR protein is in fact osmotin, a protein known to accumulate in tobacco cells in response to osmotic stress. A specific serum was obtained and used in immunoblotting experiments to study the serological relationships of TL-proteins of tobacco and to compare the induction of osmotin and acidic PR proteins R and S during the hypersensitive reaction of tobacco to tobacco mosaic virus.