A molecular approach to analyze factors affecting the mode of conidiogenesis and its diversity.

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The mode of conidiogenesis has been employed for a taxonomic criterion of higher taxa in the present taxonomy of fungi including mushrooms and basidiomycetous yeasts, however, recent numerous phylogenetic studies showed that some of these do not reflect the phylogeny. Ballistoconidium, which is made on the tip of the sterigma from the mother cell and discharged when it matures, is a one of these. When the ballistoconidium-forming activity was studied between species and among strains belonging to the same species in the genus Dioszegia, mainly D. crocea and related species, it does not necessarily reflect the phylogeny and its strength varied among strains even in the same species, indicating that formation of ballistoconidium is not a stable characteristic. Therefore, this characteristic is not appropriate as a taxonomic criterion of higher taxa, and should not be used when the reconstruction of the systematics of fungi is made.Suppression subtraction hybridization between the ballistoconidium-forming condition (media kept on a workbench in the laboratory) and the condition under which ballistoconidium not formed (media kept in a plastic container covered tightly with a lid) was performed using Bullera oryzae JCM 5281, and the difference was observed in mitochondrial gene. The morphological observation by a fluorescence microscopy showed that the mother cells with sterigma and ballistoconidia demonstrated stronger intensity than those of vegetative cells. In such mother cells and ballistoconidia, mitochondria seemed to exist near the surface of cells and occasionally cohere like particles. Based on these observations, the formation of ballistoconidium is assumed to be related to the quantitative change of mitochondria accompanied with their morphological changes.