Purification, Characterization, and Molecular Cloning of Basic PR-1-Type Pathogenesis-Related Proteins from Barley. Tomas Bryngelsson. Department of Plant Breeding Research, The Swedish University of Agricultural Sciences, S-268 31 Svalov, Sweden. Jens Sommer-Knudsen(2), Per L. Gregersen(2), David B. Collinge(2), Bo Ek(3), and Hans Thordal-Christensen(2). (2)Department of Plant Biology, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark; 3)Department of Cell Research, The Swedish University of Agricultural Sciences, P. O. Box 7055, S-750 07 Uppsala, Sweden. MPMI 7:267-275. Accepted 10 December 1993. Copyright 1994 The American Phytopathological Society.

Partial amino acid sequences of two proteins, purified from barley leaves reacting hypersensitively to the powdery mildew fungus, showed a high degree of amino acid identity to the PR-1 proteins originally described in tobacco. The proteins, subsequently designated HvPR-la and HvPR-lb, show apparent pl values of approximately 10.5 und ll, respectively and apparent M_r 15,000. Independently, differential screening of a cDNA library prepared from barley leaves, exhibiting a compatible interaction with the powdery mildew fungus, resulted in isolation of cDNA species representing two PR-1 homologs. With the exception of one amino acid, the partial amino acid sequences of HvPR-la and HvPR-lb are identical to internal sequences of the polypeptides derived from the two cDNA species. These derived polypeptides are each 164 amino acids long and both have putative N-terminal leader sequences of 24 amino acids. That these proposed leader sequences are functional is indicated by the observed occurrence of both proteins in the intercellular fluid. The proposed mature proteins (calculated M_r 14,490 and 15,204) share 91% identical amino acids with each other and 56 to 74% with other PR-1 proteins. Northern blot hybridization and Immunoblotting, respectively, show that both transcripts and both proteins accumulate following inoculation of susceptible and hypersensitively resistant barley leaves with the powdery mildew fungus.