The presence of a thaumatin-like protein, a chitinase and a glucanase among the pathogenesis-related proteins of potato (Solanum tuberosum)

Spraying the leaves of young potato plants with salicylate induces the appearance of eight major intercellular proteins that resemble the pathogenesis-related (PR) proteins of tobacco leaves. Three of these, with mol wts of approximately 21000, 26500 and 34500 have been purified to near homogeneity by chromatofocussing. Evidence from amino acid sequences, from immuno-reactivity and from absorptive properties indicates that these are, respectively, a thaumatin-like protein, an acid chitinase, and, probably a 1:3-β-glucanase. These PR-proteins also appear in the leaves of plants maturing in the glasshouse without deliberate induction.