Cerato 4

[John]

Theceratosaur was a carnivorous, swift-running North American theropod dinosaur of the Jurassic Period. It had a large skull with a short horn between the nostrils and a bony knob in front of each eye.

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Dutch elm disease is caused by the aggressive Ophiostoma novo-ulmi and the nonaggressive O. ulmi. Both secrete the protein cerato-ulmin (CU). To determine what role CU plays in the pathology of Dutch elm disease, we constructed a CU overexpression mutant of the nonaggressive O. ulmi H5. Stable integration of a single copy of the cu gene from the aggressive O. novo-ulmi into the genome of the nonaggressive isolate resulted in increased secretion of CU protein. Trials with American elm, Ulmus americana, suggested no alteration of virulence of this overexpressing transformant. Using aggressive and nonaggressive wild types, the cu overexpressing mutant, and our cu- mutant (Bowden et al., 1996), we have demonstrated that CU production is correlated with an altered phenotype and more hydrophobic and adherent yeast-like cells. Our results also demonstrate that CU has a role in protecting infectious propagules from desiccation. These biological roles for CU would affect transmission of Dutch elm disease, and we therefore propose that this hydrophobin acts as a parasitic fitness factor.

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THE recognition of aggressive strains of Ceratocystis ulmi associated with the epidemic of Dutch elm disease in Britain directed attention to the importance of variation in the pathogenicity of the causal fungus1,2. British workers3,4 have provided evidence of a correlation between pathogenicity and certain cultural characters such as colony appearance and growth rate. Here I describe a correlation between pathogenicity of certain strains of C. ulmi and the production of a metabolite named cerato-ulmin which, when introduced to elm seedlings, is capable of producing many of the symptoms of the disease.

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