The genes encoding 13 classes of pathogenesis-related (PR) proteins were examined for positive selection using maximum-likelihood (ML) models of codon substitution. The study involved 194 sequences from 54 species belonging to 37 genera. Although the sizes of the sequences examined varied from 237 bp for PR12 to 1,110 bp for PR7, most classes (9 out of 13) contained sequences made up of more th...

The synthesis of pathogenesis-related proteins (PR proteins), induced in tobacco leaves in response to infection with tobacco mosaic virus or treatment with salicylic acid, was studied with in vivo pulse-labeling experiments. PR proteins synthesis began after a lag phase of about 8 hours in leaf discs treated with salicylic acid and after more than 18 hours in those infected with tobacco mosaic...

The PR1 family of pathogenesis-related proteins from tobacco (Nicotiana tabacum L.) leaves is induced by a variety of pathogenic and chemical agents and is associated with resistance to tobacco mosaic virus. The majority of the PR1 proteins did not copurify with mesophyll protoplasts (the major cell type of the leaf) isolated from tobacco mosaic virus-infected N. tabacum cv. Xanthi-nc leaves. H...

An overview of the evolution of knowledge on the nomenclature, classification, induction, occurrence, functions, and role of pathogenesis-related proteins (PRs) is presented, covering generally the last fifteen years. The recommendations for naming and defining PRs are introduced, and the criteria required for the inclusion of new families into PRs are considered. The revision of the previous v...