Cloning Of A Gene Controlling Hyphal Growth In Magnaporthe Grisea

Magnaporthe grisea, which can infect many grasses, is the pathogenic fungus causing rice blast disease. It has been used as a model for studying interactions between plant and phytopathogenic fungi.Isolate S2514 that obtained by screening REMI transformant library is a slow-growth mutant. On the CM solid medium, hyphal growth rate of S2514 is 45% of the wild type strain P131. Also, Isolate S2514 is not only a mutant with slow hyphal growth rate but also with abnormal conidia and pathogenic deficiency. Compared with the wild strain P131, the conidia of S2514 is shorter and wider; and is completely lost its pathogenicity to the susceptible cultivar. The result of genetic analysis indicated that the change in hyphal growth, conidia morphology and pathogenicity is caused by the insertion of the plasmid through REMI.Southern blot analysis revealed that the mutant had a single site insertion of the marked plasmid in its genome and a 18kb sequence flanking the right side of insertion plasmid was yield. By comparing the flanking sequence with that of the rice blast genome, it was found that the flanking sequence was located on contig2.1938 of the Chromosome V. However the flanking sequence on left side of the insertion is located on contig2.610 of the Chromosome VII. The reason that two flanking sequences is located on different Chromosomes may be due to DNA deletion or DNA recombination during REMI. GENSCAN with the right side flanking sequence revealed a gene encodes a protein with predicted 656 amino acids was inactivate. To confirm the gene function, the flanking sequence was used as a probe to screen the genomic TAC library of the wild type strain Y34, and 9 positive clones were obtained. A fragment containing the whole gene from the positive clone was cut by Sac I and Xho I and was cloned into the vector 7afNeu with Neuomycin resistance to transform the mutant. Complementation test are in process.