title: The molecular characterization of two barley proteins establishes the novel PR-17 family of pathogenesis-related proteins.
abstract: Summary Two barley (Hordeum vulgare L.) cDNA clones (pBH6-12 and pBH6-17) were isolated from a cDNA library prepared from leaves 6 h after inoculation with Blumeria graminis f.sp. hordei (Bgh). The two transcripts accumulate strongly in response to Bgh, peaking around 6, 15-24 and 48-96 h after inoculation, concomitant with fungal penetration attempts, hypersensitive response and fungal growth. The encoded proteins, HvPR-17a and HvPR-17b, belong to a new family of plant pathogenesis-related proteins, designated 'PR-17'. The family also include NtPRp27 from tobacco (Okushima et al., 2000, Plant Mol. Biol.42, 479-488) and WCI-5 from wheat (Görlach et al., 1996, Plant Cell8, 629-643), responsive to viral and fungal infection, respectively. Antisera were raised to HvPR-17a and HvPR-17b, and the proteins exhibit apparent molecular weights of 26 and 24 kDa, respectively. They accumulate in the mesophyll apoplast following Bgh-inoculation, as well as in the leaf epidermis, the only tissue to be invaded by the fungus. Several homologous plant proteins exist, and a highly conserved part of the members of this new protein family show similarity to the active site and to the peptide-binding groove of the exopeptidase 'aminopeptidase N' from eukaryotes and the endopeptidase 'thermolysin' from bacteria.
authors.affiliation: Department of Plant Biology, Plant Pathology Section, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Anders B
authors.initials: AB
authors.lastname: Christensen
authors.forename: Baik Ho
authors.initials: BH
authors.lastname: Cho
authors.forename: Michael
authors.initials: M
authors.lastname: Næsby
authors.forename: Per L
authors.initials: PL
authors.lastname: Gregersen
authors.forename: Jakob
authors.initials: J
authors.lastname: Brandt
authors.forename: Kenneth
authors.initials: K
authors.lastname: Madriz-Ordeñana
authors.forename: David B
authors.initials: DB
authors.lastname: Collinge
authors.forename: Hans
authors.initials: H
authors.lastname: Thordal-Christensen