For investigators engaged in the study of toxins generally, and host-specific toxins in particular, it is a rare treat to attend a meeting in which toxins involved in plant pathogenesis are emphasized. A gathering of this type provides opportunity to consider the discovery of new toxins, their chemical structures, genes encoding enzymes that control their biosyntheses, their sites of action and physiological effects on plants, and their roles (if any) in pathological processes. Having acknowledged the inspiration fostered by a 'toxin meeting', however, it is important to point out that the program of this symposium was generously sprinkled with 'nontoxin' talks. These contributions generated cross-disciplinary discussion and promoted new ways of thinking about relationships among factors required for plant disease development. The point can be illustrated by considering just one example. We have in the past often regarded diseases mediated by host-specific toxins and diseases involving 'gene-for-gene' relationships as representing two different classes of fungal/plant interaction. This is largely because the key molecular recognition event in so-called 'toxin' diseases leads to compatibility, whereas the corresponding event in 'gene-for-gene' diseases leads to incompatibility. Yet the race specific elicitors produced by the 'gene-for-gene' fungi Cladosporium fulvum (De Wit, Adv. Bot. Res. 21:147- 185, 1995) and Rhynchosporium secalis (Rohe et a1. , EMBO J.

Zusammenfassung
Proceedings of the 3rd Tottori International Symposium on Host-Specific Toxins, Daisen, Tottori, Japan, August 24-29, 1997

Inhalt
Toxin Biosynthesis.- A mechanistic view of the fungal/plant interaction based on host-specific toxin studies.- Function and biosynthesis of trichothecenes produced by Fusarium species.- Enzymology, molecular genetics, and regulation of biosynthesis of the host-selective toxin HC-toxin.- Host-specific toxin deficient mutants of the tomato pathotype of Alternaria alternata obtained by restriction enzyme-mediated integration.- Molecular analysis of AK-toxin biosynthesis in the Japanese pear pathotype of Alternaria alternata.- A catalytic domain of a cyclic peptide synthetase that is specific for the apple pathotype of Alternaria alternata and its possible involvement in host-specific AM-toxin production.- Involvement of host factors in the production of a protein host-specific toxin produced by Alternaria brassicicola.- Structures and biosyntheses of phytotoxins in Cochliobolus spicifer and Bipolaris sorokiniana: C3 Unit addition reaction in phytotoxin biosyntheses.- Versatile synthetic route for AAL-toxins and fumonisins.- Characterization of the thiotemplate mechanisms of syringomycin and syringopeptin synthesis by Pseudomonas syringae pv. syringae.- Effects of Toxins on Plants.- HC-toxin: Does inter-species chromatin remodeling confer host-pathogen compatibility?.- Victorin-induced oat cell death.- Primary effect of a host-selective toxin from Magnaporthe grisea to mitochondria of rice leaves.- The accelerated effects of AK-toxin I on exocytosis and endocytosis of susceptible Japanese pear leaves.- Isolation and mode of action of Ptr chlorosis toxin from Pyrenophora tritici-repentis.- Syringolide derivatives for receptor studies.- Lethal logic in apoptosis: toxins trigger programmed cell death during disease in eukaryotic cells.- Evolution and Genetics of Toxin Production and Pathogenesis.- Evolution of pathogenic and reproductive strategies in Cochliobolus and related genera.- On the phylogenetic correlations of phytotoxins and related metabolites among blast disease fungi.- Cloning and expression of the ToxA gene in Pyrenophora tritici-repentis.- The Ptr necrosis toxin and necrosis toxin gene from Pyrenophora tritici-repentis.- The genetics of pathogenicity in Cochliobolus heterostrophus.- Toxins and other metabolites of Phoma tracheiphila involved in pathogenesis of mal secco disease of citrus trees.- Ergopeptine toxins and peptide synthetase genes in clavicipitaceous pathogens and symbionts of plants.- Genetical and physiological studies on the species-specific parasitism of Magnaporthe grisea in gramineous plants with a special reference to a cross between the Triticum isolate and the Setaria isolate.- Sensing, Penetration and Host Degradation.- Signal transduction and gene expression during early stages of fungal phytopathogenesis in the rice blast fungus.- Cell wall degrading enzymes in HST-producing fungal pathogens.- Expression and regulation of melanin biosynthetic genes during appressorium formation of Colletotrichum lagenarium.- Mechanics of invasive fungal growth and the significance of turgor in plant infection.- The involvement of fungal cutinase in early processes of plant infection.- Biochemical and molecular roles of HST and enzymes produced by pathogen of citrus brown spot disease.- Infection behavior of Venturia nashicola and supposed involvement of cell-wall degrading enzymes in the pathogenesis on Japanese pear.- Host components and a complex bacterial sensor kinase, RtpA, determine the pathogenic process of Pseudomonas tolaasii on a cultivated mushroom, Pleurotus ostreatus.- Mechanisms of Plant Resistanceand Susceptibility.- Molecular analysis of the polygalacturonase-inhibiting protein(PGIP) gene family in Phaseolus vulgaris L..- Saponin detoxification and fungal pathogenesis.- The interaction of Alternaria alternata f. sp. lycopersici and its AAL-toxins with tomato.- The oxidative burst system in plants: a strategic signal transduction system for triggering active defense and for parasites to overcome.- Plant cell wall with the suppressor may play a crucial role in determining specificity.- Characterization of the interaction between fungal pathotoxins and URF13, the cms-T maize mitochondrial T-toxin receptor.- Identification of receptor site of the suppressor isolated from Phytophthora infestans in potato plasma membrane by using surface plasmonl biosensor.- Detoxification of mycotoxins in planta as a strategy for improving grain quality and disease resistance: identification of fumonisin-degrading microbes from maize.- Molecular cloning, expression and characterization of recombinant antibody against mycotoxins.- Selection of a resistant mutant to Alternaria blotch in apple and analysis of proteins associated with the susceptibility by 2-D gel electrophoresis.- Several strategies for dissecting and controlling functions in plant cells.