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Alternaria species are mainly saprophytic fungi, but some are plant pathogens. Seven pathotypes of Alternaria alternata use secondary metabolites of host-specific toxins as pathogenicity factors. These toxins kill host cells prior to colonization. Genes associated with toxin synthesis reside on conditionally dispensable chromosomes, supporting the notion that pathogenicity might have been acquired several times by A. alternata. Alternaria brassicicola, however, seems to employ a different mechanism. Evidence on the use of host-specific toxins as pathogenicity factors remains tenuous, even after a diligent search aided by full-genome sequencing and efficient reverse-genetics approaches. Similarly, no individual genes encoding lipases or cell wall-degrading enzymes have been identified as strong virulence factors, although these enzymes have been considered important for fungal pathogenesis. This review describes our current understanding of toxins, lipases, and cell wall-degrading enzymes and their roles in the pathogenesis of A. brassicicola compared to those of other pathogenic fungi. It also describes a set of genes that affect pathogenesis in A. brassicicola. They are involved in various cellular functions that are likely important in most organisms and probably indirectly associated with pathogenesis. Deletion or disruption of these genes results in weakly virulent strains that appear to be sensitive to the defense mechanisms of host plants. Finally, this review discusses the implications of a recent discovery of three important transcription factors associated with pathogenesis and the putative downstream genes that they regulate.

In search for novel metabolites from the culture broth of the mushroom Stereum hirsutum, three new tricyclic sesquiterpenes named hirsutenols A (1), B (2), and C (3) have been isolated. Their structures were assigned on the basis of various spectroscopic studies.

Free radicals are involved in the pathogenesis of various human diseases. There is growing interest in new free radical scavengers having the potential as protective agents against active oxygen-related human diseases1,2).In search for new antioxidants3-5), we have discovered a basidiomycete strain of Stereum hirsutum as a producer of antioxidative compounds. The genus Stereum is known to produce various sesquiterpenes, benzaldehydes and benzofurans6-8). We herein describe the fermentation of the producing strain, isolation, structure determination and antioxidative activity of sterins A and B.The sterins-producing strain was generated from tissue culture of the fruiting body of Stereum hirsutum collected at Dukyu-National Park, Korea and was confirmed as a basidiomycete strain by formation of clamp-connection.The strain grown on potato sucrose agar medium was used to inoculate two 500ml Erlenmeyer flasks containing 100ml of the seed medium consisting of yeast extract 0.4%, malt extract 1.0% and glucose 0.4% (pH 6.0 before sterilization The above NMR spectral analyses indicated that the aglycone of sterin A was closely related to 6-methoxy-2,2-dimethylchromene, a fungal metabolite from the mushrooms Lactarius fuliginosus and L. picinus9). The furanose was assigned by the 1H-1H COSY experiment, and its chemical shifts and 1H coupling constants suggested to be ribose10). The structure of sterin A was assigned by the HMBC experiment, which showed the long-range 150.3 (Table 1). Therefore the structure of sterin A was determined as a chromene glycoside. The deduced structure was supported by ESI-mass measurement in positive ion mode showing a molecular ion peak at m/z 331 (M+Na)+.The molecular formula of sterin B was established as C12H14O3 by high-resolution EI-mass measurement (m/z 206.0949 M+ +0.6mmu). Sterin B was readily decomposed in room temperature. The 1H NMR spectrum of sterin B showed the signals attributable to an aldehyde

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