Evidence for the requirement of extracellular protease in the pathogenic interaction of Pyrenopeziza brassicae with oilseed rape
1991
Ball, A.M. | Ashby, A.M. | Daniels, M.J. | Ingram, D.S. | Johnstone, K.
Using a detached cotyledon test for pathogenicity, a UV-induced, non-pathogenic mutant of Pyrenopeziza brassicae was isolated which was also deficient in extracellular protease production in vitro. The proteolytic activity in the wild type was apparently due to a single cysteine protease with a mol. wt of 34 k, a temperature optimum of 40 degrees C and a pH optimum of 8. When the mutant was crossed with a wild-type isolate of P. brassicae, the non-proteolytic and non-pathogenic traits co-segregated in the resulting progeny. The protease-mutant was transformed with clones from a genomic library of P. brassicae and a transformant obtained which had a single cosmid insert and showed concomitant restoration of pathogenicity and proteolytic activity in vitro. These results suggest that extracellular protease is a pathogenicity determinant of P. brassicae and possible functions for this protease in the disease process are discussed.
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