Molecular characterization of messenger RNAs for ‘pathogenesis-related’ proteins 1a, 1b and 1c, induced by TMV infection of tobacco

Abstract

A cDNA library was made to poly(A)‐containing RNA from tobacco mosaic virus (TMV)‐infected Samsun NN tobacco plants and clones corresponding to mRNAs for the ‘pathogenesis‐related’ (PR) proteins 1a, 1b and 1c were identified. One clone was found to contain a complete copy of PR‐1b mRNA. The structural organization of this RNA is: a leader sequence of 29 nucleotides, an open reading frame of 504 nucleotides encoding a 30 amino acid long signal peptide and a 138 amino acid long mature protein, and a 3′‐non‐coding region of 235 nucleotides. Two other clones were found to contain partial copies of PR‐1a and PR‐1c mRNAs. The data indicate an ∼90% homology between the amino acid sequences of PR‐1a, ‐1b and ‐1c. Using one of the clones as probe it was shown that in the TMV‐inoculated lower leaves and the non‐inoculated upper leaves of a tobacco plant, the PR‐1 mRNAs become detectable from 2 and 8 days after inoculation, respectively.