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Melanins, the pigments mainly responsible for black discoloration of weathered barley and malt after infection with dematiaceous fungi such as Alternaria spp. and Drechslera spp., are anti-stress compounds with antioxidant abilities but also function as virulence factors during invasion of the host plant (Henson et al., 1999). Other fungal pigments seem to have no known adverse effects and their exploitation as natural colorants in the food industry is hence intensively studied (Duran et al., 2002; Mapari et al., 2005, 2010).

Fungal hormones

Fungal hormones are a group of secondary metabolites to which a function can clearly be attributed. They are produced by cells as very specific molecules that have morphogenetic effects on other cells of the same or closely related species and are aimed at regulating and coordinating the temporal and spatial sequence of events leading to the pairing and fusion of nuclei of two cells during sexual reproduction (see reviews by Gooday, 1974 and by Gooday and Davis, 1993). The mechanism of selective attraction of mating partners may involve the mutual production of compounds binding specifically to hormone receptors on or in the respective partner and triggering the morphogenetic differentiations leading to sexual reproduction like in Saccharomyces cerevisiae (Herskowitz, 1988). In other species, one of the two mating partners produces a hormone that triggers morphogenetic differentiation in the other. Production of anther- idiol in the water mould Achlya spp. would be an example for this type (Gooday, 1974). The third type of mechanism is the mutual production of two different precursors by each mating partner, which mutually supplements a biosynthetic pathway in the respective mating partners resulting in the production of a compound that triggers the formation of mating organs in both partners. This type of mechanism can be found in the Mucorales such as in Mucor spp. or Rhizopus spp. (Werkman and van den Ende, 1974).

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