Functional Analysis and Identification of the Pathogenicity-Related Genes and Mating-Type Genes in Rice Blast Fungi, Magnaporthe grisea.

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From our differential cDNA library of Magnaporthe grisea at appressorium formation constructed by subtracting cDNA clones expressing in mycelial growth, some candidates clones were selected by the DNA macro array and the RT-PCR methods as the pathogenicity/virulence-related genes strongly expressed at appressorium formation and/or early infection stage. Of the genes, we selected 3 genes, FMI1 (Functional gene of Magnaporthe Infection 1 ; clone #B19), FMI2 (clone #B48) and MGH61A (Magnaporthe Glycoside Hydrase family 61A ; clone #B59), which were more specifically expressed during early infection stage. These gene and genomic structures were analyzed in detail and also the gene-destructed mutants were created by homologous recombination to elucidate the potential physiological functions. The FMI1 gene encoded the serine-rich partial sequence and a signal peptide to localize in nucleus at N-terminus of the amino acid sequence, and also partial homologous sequence to sucrase/ferredoxin at … More the C-terminus. The FMI2 gene encoded a part of the active domain homologous to dual specificity phosphatase. The FMI1 and FMI2 genes-destructed mutants abnormally formed appressoria and delayed in infection, although their affects were limited during early infection stage and overcome by the visible lesion formation. The MGH61A gene provably was a secreted-type protein with a signal peptide, encoding highly homologous sequence domain to glycoside hydrase family 61 at 5'-end. The gene-destructed mutants descended significantly in appressorium formation, infection and lesion formation.Many isolates of Magnaporthe grisea were collected worldwide, mainly from Vietnam, to check the pathogenic race and natural crossing ability. Except the standard isolates found in Yunnan in China and made in USA, no isolate having high ability to cross was found, although many kinds of pathogenic races were found in our collections. Interestingly a very novel and unique double strands RNA virus was found in Vietnam isolates. The RNA virus easily infected to another healthy isolate and caused to decline the growth and virulence. Less