G M Ballance, L Lamari, R Kowatsch and C C Bernier.
Department of Plant Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
G M Ballance, Department of Plant Science, University of Manitoba, Winnipeg, MB
R3T 2N2, Canada
telephone: 204 474 6086 fax: 204 261 5732 email: firstname.lastname@example.org
Accepted: 9 December 1996
Pyrenophora tritici-repentis differentially induces necrosis and chlorosis in its wheat host. Necrosis-inducing (nec+) isolates produce the Ptr necrosis toxin, a 14 kD protein, responsible for the induction of necrosis in necrosis-developing wheat genotypes. A cDNA expression library was constructed and screened with anti-Ptr necrosis toxin antiserum. A 900 nucleotide cDNA clone (PtrNEC), encoding a 19.7 kD protein precursor of the Ptr necrosis toxin was isolated. In addition to the antigenicity of its product, the identity of the clone was confirmed by i) the occurrence of a series of codons which exactly describe a 24 amino acid sequence from a Ptr necrosis toxin peptide, ii) the close similarity of the clone-derived amino acid composition to that of the Ptr necrosis toxin, and iii) the identical cultivar sensitivity-range for the E. coli-expressed cDNA product to that of pathogen-produced Ptr necrosis toxin. Genomic DNA was screened from a number of fungal isolates of nec+ and nec- pathotypes using the full length PtrNEC clone. A single hybridization band was detected in nec+ isolates, but was absent from nec- isolates.