Study on molecular mechanism of physiological specialization in Fusarium oxysporum

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Study on transformation and cell fusion of Fusarium oxysporumTo investigate on physiological specialization of F.oxysporum, effort was made to establish the transformation system of Fusarium fungus to confer drug resistance for selection of the fused cells. The plasmid pHL1 carrying hygromycinB-resistant gene was introduced into the fungal protoplasts of F.oxysporum f. sp. lycopersici by PEG method. The resuleted hygromycin B-resistant colonies were selected in degree of tolerance and in pathogenicity to tomato plants, and R7-HygB transformant was isolated. On the other hand, F.oxysporum f. sp.cucumerinum was transformed directly into the germed spores treated with Novozyme 234 by electropolation method.Study on virulence factor in wilt fungus of tomatoThe wilt fungus F.oxysporum f. sp. lycopersici produces various kinds of pectinases as well as fusaric acid as virulence factors. One of pectinases, polygalacuturonase (PG), has been speculated as an important agent for virulence. The fungal cells were mutagenized and selected in non-pathogenicity. The obtained mutant OW932 was shown to be a very weak pathogen This mutant was slight content in PG protein as compared with the parent strain, indication that PG plays an important role pathogenicity of F.oxysporum. After purification of the enzyme, SDS-PAGE and electrophoresis analyzes showed 4 kinds of isozymes. In further study, PG was located only at vascular bundle in diseased tomato tissues when PG reaction was detected using PG-antiserum. Thus, wilt symptom caused by F.oxysporum f. sp. lycoperisici may be damage of vascular bundle cells by the fungal PG.