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Proteins obtained from seedling shoots and floral meristems of Sorghum bicolor (L.) Moench cv. NK 1210 induced mycelial growth in the smut fungus, Sporisorium reilianum in vitro. Proteins precipitated with trichloroacetic acid and ammonium sulfate were equally effective as inducers, although there were minor variations in the pattern of mycelial growth. Hydrolysis of the protein fraction with the proteolytic enzyme pronase E resulted in considerable reduction in the proteins' ability to induce mycelial growth. Digestion of the protein fraction with driselase, resulted in a slight enhancement of biological activity. The results suggest that amino sugar moieties in glycoproteins may act as inducers of mycelial growth in Sporisorium reilianum. [ABSTRACT FROM AUTHOR]

Sporisorium reilianum, the fungus that causes sorghum head smut, was grown with sucrose, lactose, trehalose or raffinose in liquid suspension or on a solid medium. Liquid culture media were analyzed for hydrolysis products of these carbohydrates to determine extracellular enzyme activity of the fungus. Increased amounts of glucose and fructose in the culture medium of S. reilianum grown with sucrose or raffinose indicated that invertase (β-fructofuranosidase, 3.2.1.26) activity was present. No evidence of extracellular galactosidase or trehalase activity was found. Enhanced sporidial colony formation on carbohydrates that can be hydrolyzed to hexoses, and specific forms of mycelial growth on lactose, trehalose or on a carbohydrate-deficient medium might suggest that mycelial growth is a way of foraging for food sources. However, the rapid and profuse mycelial growth on the host cell wall glycoprotein appears to be in response to abundant food supply (probably of a different type). Therefore availability of different kinds of carbon sources in the environment of the growing fungus might determine dimorphism and associated pathogenesis by S. reilianum. [ABSTRACT FROM AUTHOR]