title: Homologous recombination causes the spontaneous deletion of AVR-Pia in Magnaporthe oryzae.
abstract: AVR-Pia, an avirulence gene in the genome of the rice blast fungus Magnaporthe oryzae, triggers a hypersensitive reaction in rice cultivars harbouring the resistance gene Pia. The copy number of AVR-Pia was revealed to vary from one to three among M. oryzae isolates avirulent to Pia rice, and three copies of the gene were located on a single chromosome in strain Ina168, from which the gene was originally cloned. The spontaneous avr-Pia mutant originated from Ina168, named Ina168m95-1, which lacks the AVR-Pia gene, and was therefore used to elucidate the molecular mechanism of the deletion of all three copies of AVR-Pia. Screening and analysis of cosmid clones indicated that two copies of the DNA-type transposon Occan (Occan(9E12)  and Occan(3A3) ) were located on the same chromosome, and three copies of AVR-Pia were located in between the two Occan elements. Ina168m95-1 contains a conserved Occan element, named Occan(m95-1) , between sequences homologous to the 5'-flanking region of Occan(3A3)  and the 3'-flanking region of Occan(9E12) . In addition, sequence polymorphisms indicated a homologous recombination between Occan(3A3)  and Occan(9E12) , which resulted in Occan(m95-1) . Based on these observations, we propose the hypothesis that homologous recombination in the two Occan elements leads to the deletion of AVR-Pia in Ina168m95-1.
authors.affiliation: Hokkaido University, Sapporo, Japan. sonet@chem.agr.hokudai.ac.jp
authors.forename: Teruo
authors.initials: T
authors.lastname: Sone
authors.forename: Saori
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Miki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Satoh
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ohtsuka
authors.forename: Ayumi
authors.initials: A
authors.lastname: Abe
authors.forename: Kozo
authors.initials: K
authors.lastname: Asano
mesh_terms: D004251:DNA Transposable Elements; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005800:Genes, Fungal; D059765:Homologous Recombination; D020082:Magnaporthe / Q000235:genetics* / Q000472:pathogenicity; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion
chemical_list: D004251:DNA Transposable Elements; D004271:DNA, Fungal