4 Abstract The aim of this study was to determine whether oribatid mites affect the variety of fungi in litter of Scots pine (Pinus sylvestris), and if the dispersibility of fungi particles is related to oribatid mite species. To this end, I have prepared several semi-natural systems, in which I observed dispersion of fungi separately and in the presence of two oribatid mite species: Phthiracarus sp. and Adoristes ovatus. I assessed the experiment in two ways, by a cultivation of washed needles on agar medium and direct observation of needles under a binocular magnifier. In the next part of this study I isolated particles of fungi present on the surface and in the faeces of oribatid mites Adoristes ovatus, Porobelba spinosa and Spatiodamaeus verticillipes and compared it with the respective oribatid mite species. The most frequent needles fungi spread by oribatid mites were Oidiodendron maius var. maius, Oidiodendron muniellense, Oidiodendron setiferum, Umbelopsis ramanniana, Mucor hiemalis f. hiemalis and Mortierella hyalina. On the mites body surface the most commonly recorded fungi were Beauveria bassiana, Umbelopsis ramanniana, Cladosporium cladosporioides s.l., Cladosporium herbarum s.l. and unknown species of the genus Penicillium. Fungi species Acrodontium crateriforme, Umbelopsis ramanniana and...

Dothistromin (DOTH) is a secondary metabolite produced by the fungal peanut pathogen Passalora arachidicola and pine needle pathogen Dothistroma septosporum. The chemical structure of DOTH is similar to a precursor of aflatoxin (AF) and sterigmatocystin (ST), which are secondary metabolites produced by Aspergillus species. A size fractionated genomic library was made and 11 putative DOTH genes were identified in P. arachidicola. The DOTH genes in P. arachidicola were compared to DOTH genes in D. septosporum as well as to AF and ST genes in Aspergillus species. The DOTH gene products in P. arachidicola showed 73 - 96% amino acid identity to DOTH genes in D. septosporum and 50 - 69% amino acid identity to AF/ST genes in Aspergillus. The DOTH biosynthesis genes in P. arachidicola had similar gene organization and direction of transcription to DOTH biosynthesis genes in D. septosporum and is similar in that 11 putative DOTH genes are separated into three mini-clusters. This differs from the AF/ST clusters in which 25 AF/ST genes are tightly clustered in a 70 kb region. Identification of transcription factor binding sites upstream of DOTH genes in P. arachidicola and D. septosporum suggested similar co-regulation of DOTH gene expression in P. arachidicola and D. septosporum. Tandem and inverted repeat sequences were identified in intergenic regions in the P. arachidicola DOTH gene cluster, but the distribution of those repeats appears to be random. This suggests that the fragmentation of the DOTH biosynthesis gene cluster is not due to retrotransposon activity or recombination between repeat sequences. The DOTH biosynthesis gene clusters in P. arachidicola and D. septosporum could be ancestral to AF/ST biosynthesis clusters in Aspergillus species.

第22回名古屋大学年代測定総合研究センターシンポジウム平成21(2009)年度報告