Cloning of genes concerned in pathogenicity of plant pathogens

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The aim of this project is to analyze the pathogenicity of plant pathogens at molecular lecel, and to lay the foundation of disease control.1. The analysis of essential factors for penetration of colletorichum laqenarium. Three mutants of C. lagenarium, with appressoria that could not penetrate nitrocellulose. From the results of scanning electron microscopic observation, one mutant (83182) formed a penetration peg and restored appressorial penetration swithout halo formation in the presence of Czapek liquid medium. Therefore, it found that mutant 83182 is deficient in secretion system for cellulase.2. Purification of a melanin biosyunthesis enzyme converting scytalon to THN. a melanin biosynthe-tic enzyme, scytalone dehydratase, which converts scytalone to thn was purified from mycelia of cochliobolus miyabeanus. This enzyme had an optimum pH near 8.2 and mol w 23,000 Da. The amino acid sequence of N"terminal of this enzyme was decided using an amino acid analyzer and origonucleotides … More corresponded to the amino acid sequence were synthesized. The origonucleotide was used for screening of cDNA of mRNA and 12 clones were obteined.3. Genetic analysis of genes involved in melanin biosynthesis of cochliobolus miyabeanus. color mutants of C. miyabeanus defective in melanin biosynthesis were isolated. Although the wild-type strain KU-13 formed dark green colonies, color mutants formed white,brown, and gray or white colonies with red pigment secretion. From the white mutant which secreted red pigment, designated scy, a melanin precoursor which restored melanization of albino mutants alm-l was isolated and identified as scytalone. This indicated that scy mutant was defective in the convertion of scytalone to THN and that melanin of this fungus is of pentaketide origin formed from 1,8-DHN. Grown mutant brm were considered to be defective in the convertion of 1,3,8-THN to yermelone. Albino mutant alm-2 whose coloration was not restored by application of scytalone were also isolated. From crossing experiments among the color mutants, it was indicated that alm-1. alm-2 and brm were liked and that scy segregates independently regulating the pentaketide cyclization and vonversion of scytalone. Less