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The Significance of Hydrophobins
Mycological Research News genic Beauveria brongniartii by the use of sensitive HPLC and MS techniques (pp. 1227–1233). Conidia of another entomopathogen, Aschersonia aleyrodis, germinated to different degrees and persisted to different extents on three host plants tested ; this is reflected in the extent of mortality in the whitefly hosts (pp. 1234–1240). In Conidiobolus adiaeretus, two kinds of conidia can be produced, repetitional microconidia and capilliconidia, calling into question subdivisions of the genus based on the occurrence of one of these conidium types (pp, 1270–1275).
1154 A high α-amylase producing strain of Aspergillus oryzae has been discovered in glucose-limited continuous culture which has a higher growth rate and more sparsely branched mycelium than the parent strain (pp. 1241–1249). Rust fungi are notoriously difficult to grow in pure culture, but success in Melampsora larici-tremulae has been obtained by seeding aeciospores onto defined media (pp. 1250–1257). The organelle arrangement in ‘ gun cell ’ differentiation in the enigmatic nematophagous Haptoglossa dickii has been elegantly documented ultrastructurally (pp. 1258–1269).
THE BMP1 GENE PROVIDES A CLUE TO INFECTIVITY IN PLANT PATHOGENIC FUNGI Why some fungi are serious plant pathogens and others not is a question that has remained unanswered. New studies on mutant strains of the grey mould fungus Botrytis cinerea, the anamorph of Botryotinia fuckeliana, may provide a clue to the answer. Zheng et al. (2000) studied infectivity in strains lacking the Botrytis mitogen-activated protein (MAP) kinase gene required for pathogenesis (BMP1). Strains lacking the gene were not pathogenic to carnations, but when the wildtype gene was reinserted into the mutant strains, pathogenicity was restored. The strains lacking the gene also had a lower growth rate but produced normal conidia and mycelia. The work is of especial interest as the rice blast fungus Magnaporthe grisea also has a MAP gene essential for its pathogenicity, and the gene in Botrytis cinerea was discovered by isolating homologues of the Magnaporthe gene from the Botrytis. The sequences of the amino acids in the mitogen activated proteins in these fungi were also found to be similar to those of the same protein in a range of other plant
pathogenic fungi, notably Colletotrichum heterostrophus, C. lagenarium, Haemonectria haematococca, and Ustilago maydis. Small differences between the sequences were found and a phylogram showing these prepared. It is fascinating that the same gene or close homologues are found in such a diverse range of fungi belonging to different orders and even phyla. The genes are evidently highly conserved, originated early in fungal evolution, and seem to have been lost in some fungi but retained in others. In addition to aiding our understanding of pathogenicity in known pathogens, checking for MAP genes in other fungi has the potential to indicate the possible pathogenicity and risk posed by newly discovered or less well-studied fungi.
Zheng, L., Campbell, M., Murphy, J., Lam, S. & Wu, J.-R. (2000) The BMP1 gene is essential for pathogenicity in the gray mold fungus Botrytis cinerea. Molecular Plant-Microbe Interactions 13 : 724–732.
THE SIGNIFICANCE OF HYDROPHOBINS Hydrophobins, proteins present as rodlets on hyphal walls and sometimes secreted into the medium, have come to be appreciated as a key feature of the success of fungi, especially through the elegant studies of Joseph G. H. Wessels and his colleagues in The Netherlands. A useful and succinct synopsis of their importance has been provided by Wessels (1999). Hydrophobins have been established or suggested as having roles in an amazing array of aspects of fungal biology : the emergence of aerial structures by lowering surface tension and preventing wetting ; preventing conidia clumping when wet and so facilitating their dispersal ; protecting fungi from attack ; aiding adhesion to plant and animal surfaces ; adhesion
of germ tubes and appressorium formation ; formation of ectomycorrhizas ; facilitating lichenization by lining air spaces in lichen thalli ; eliciting plant defences ; preventing plant enzymes releasing elicitors from plant pathogenic fungi or attacks by animal immune systems ; as toxins of necrotrophic fungi ; and in hyphal wall construction. For those wanting to discover more about any of these multifarious and fascinating aspects of hydrophobins, Wessels provides an extensive entre! e into the pertinent literature. Wessels, J. G. H. (1999) Fungi in their own right. Fungal Genetics and Biology 27 : 134–145.
1154 A high α-amylase producing strain of Aspergillus oryzae has been discovered in glucose-limited continuous culture which has a higher growth rate and more sparsely branched mycelium than the parent strain (pp. 1241–1249). Rust fungi are notoriously difficult to grow in pure culture, but success in Melampsora larici-tremulae has been obtained by seeding aeciospores onto defined media (pp. 1250–1257). The organelle arrangement in ‘ gun cell ’ differentiation in the enigmatic nematophagous Haptoglossa dickii has been elegantly documented ultrastructurally (pp. 1258–1269).
THE BMP1 GENE PROVIDES A CLUE TO INFECTIVITY IN PLANT PATHOGENIC FUNGI Why some fungi are serious plant pathogens and others not is a question that has remained unanswered. New studies on mutant strains of the grey mould fungus Botrytis cinerea, the anamorph of Botryotinia fuckeliana, may provide a clue to the answer. Zheng et al. (2000) studied infectivity in strains lacking the Botrytis mitogen-activated protein (MAP) kinase gene required for pathogenesis (BMP1). Strains lacking the gene were not pathogenic to carnations, but when the wildtype gene was reinserted into the mutant strains, pathogenicity was restored. The strains lacking the gene also had a lower growth rate but produced normal conidia and mycelia. The work is of especial interest as the rice blast fungus Magnaporthe grisea also has a MAP gene essential for its pathogenicity, and the gene in Botrytis cinerea was discovered by isolating homologues of the Magnaporthe gene from the Botrytis. The sequences of the amino acids in the mitogen activated proteins in these fungi were also found to be similar to those of the same protein in a range of other plant
pathogenic fungi, notably Colletotrichum heterostrophus, C. lagenarium, Haemonectria haematococca, and Ustilago maydis. Small differences between the sequences were found and a phylogram showing these prepared. It is fascinating that the same gene or close homologues are found in such a diverse range of fungi belonging to different orders and even phyla. The genes are evidently highly conserved, originated early in fungal evolution, and seem to have been lost in some fungi but retained in others. In addition to aiding our understanding of pathogenicity in known pathogens, checking for MAP genes in other fungi has the potential to indicate the possible pathogenicity and risk posed by newly discovered or less well-studied fungi.
Zheng, L., Campbell, M., Murphy, J., Lam, S. & Wu, J.-R. (2000) The BMP1 gene is essential for pathogenicity in the gray mold fungus Botrytis cinerea. Molecular Plant-Microbe Interactions 13 : 724–732.
THE SIGNIFICANCE OF HYDROPHOBINS Hydrophobins, proteins present as rodlets on hyphal walls and sometimes secreted into the medium, have come to be appreciated as a key feature of the success of fungi, especially through the elegant studies of Joseph G. H. Wessels and his colleagues in The Netherlands. A useful and succinct synopsis of their importance has been provided by Wessels (1999). Hydrophobins have been established or suggested as having roles in an amazing array of aspects of fungal biology : the emergence of aerial structures by lowering surface tension and preventing wetting ; preventing conidia clumping when wet and so facilitating their dispersal ; protecting fungi from attack ; aiding adhesion to plant and animal surfaces ; adhesion
of germ tubes and appressorium formation ; formation of ectomycorrhizas ; facilitating lichenization by lining air spaces in lichen thalli ; eliciting plant defences ; preventing plant enzymes releasing elicitors from plant pathogenic fungi or attacks by animal immune systems ; as toxins of necrotrophic fungi ; and in hyphal wall construction. For those wanting to discover more about any of these multifarious and fascinating aspects of hydrophobins, Wessels provides an extensive entre! e into the pertinent literature. Wessels, J. G. H. (1999) Fungi in their own right. Fungal Genetics and Biology 27 : 134–145.