Comparative study of two groups of b proteins (pathogenesis related) from the intercellular fluid of Nicotiana leaf tissue infected by tobacco mosaic virus

Abstract

A time-course study showed that the major extracellular b (pathogenesis-related) proteins were detected approximately 37 h after tobacco mosaic virus infection of Nicotiana tabacum L. cv. Xanthi-nc tobacco leaf tissue. Silver staining of b1b2 and b3 proteins in native polyacrylamide gels required previous staining with Coomassie blue. Elution profiles of b4, b5, and b6b proteins from DEAE-Sephacel columns were similar to those of b1b2, and b3 proteins. Relationships among b proteins accumulating in the intercellular fluid of hypersensitive cv. Xanthi-nc tobacco leaves infected by tobacco mosaic virus were examined on the basis of serological relationships and by comparing peptide fragments. Results showed that b4, b5, and b6b proteins share common antigenic determinants and polypeptide fragments different from those shared by b1b2, and b3 proteins. Together with the close similarity of the molecular weights of the proteins within each group, these data suggest that at least two groups of related proteins are found in the intercellular fluid extracts of tobacco plants infected by tobacco mosaic virus. It is also shown that the antigenic determinants shared within the b4, b5, and b6b group are found with the same b proteins from systemically infected N. tabacum L. cv. Samsun and with some b proteins from N. sylvestris Speg. and Comes.