Detection of pathogenesis-related proteins (PR or b) and of other proteins in the intercellular fluid of hypersensitive plants infected with tobacco mosaic virus

Abstract

In tobacco mosaic virus infected hypersensitive Nicotiana species, the pathogenesis-related (PR) or b proteins were found with other proteins in the intercellular fluid of leaf tissue. Analysis of leaves from mock-inoculated plants did not reveal the presence of detectable amounts of proteins in the intercellular fluid. The presence of proteins in the intercellular fluid seems to be widespread since 10 proteins were detected in tobacco mosaic virus infected Chenopodium quinoa Willd. These proteins were found not only in inoculated tissue but also in the intercellular fluid of uninoculated upper leaves. A two-dimensional gel electrophoretic analysis of intercellular fluid proteins from N. tabacum L. cv. Xanthi-nc infected leaves showed that the relative molecular weight of protein b2 is larger (14 700) than the one of b1 and b3 (14 200). Other proteins, ranging in molecular weights from 12 500 to 36 300, could also be detected. We postulate that the presence of rather large amounts of proteins, including the well-characterized b proteins, in the intercellular fluid of infected hypersensitive leaves reflects overall changes in cell-to-cell interactions and in the cell wall metabolism.