title: Loss of a 1.6 Mb chromosome in Pyricularia oryzae harboring two alleles of AvrPik leads to acquisition of virulence to rice cultivars containing resistance alleles at the Pik locus.
abstract: A small and extra chromosome of 1.6 Mb was previously identified in a Pyricularia oryzae strain, 84R-62B. To understand a role of the 1.6 Mb chromosome in the pathogenic changeability of P. oryzae, we performed experiments designed to characterize the 1.6 Mb chromosome in the present study. A gene family encoding secreted protein Pex31s in P. oryzae consists of five homologs, Pex31-A to -E. Among them, Pex31-A and -D are known to be recognized by Pik-m and Pik/Pik-m/Pik-p, respectively. In the present study, we identified Pex31-A and -D in the genome of 84R-62B. Segregation analyses using an F1 population between 84R-62B and another rice blast strain, Y93-245c-2, revealed a strong linkage between the two homologs and the 1.6 Mb chromosome of 84R-62B. A CHEF-Southern analysis revealed an association between the 1.6 Mb chromosome and the homologs, indicating that both homologs are located on the 1.6 Mb chromosome of 84R-62B. The loss of the 1.6 Mb chromosome was observed in subcultures of a F1 progeny, F1-327. These subcultures concomitantly acquired virulence on Pik, Pik-m, and Pik-p. The present study is the first report showing that loss of a small and extra chromosome leads to pathogenic mutation of P. oryzae and may provide a new insight into the mechanisms generating pathogenic variation of this fungus.
authors: Laboratory of Plant Pathology, Faculty of Agriculture, Saga University, Saga, Saga, 840-8502, Japan, mkusaba@cc.saga-u.ac.jp.
authors: Motoaki
authors: M
authors: Kusaba
authors: Taiga
authors: T
authors: Mochida
authors: Takeshi
authors: T
authors: Naridomi
authors: Yoshikatsu
authors: Y
authors: Fujita
authors: Izumi
authors: I
authors: Chuma
authors: Yukio
authors: Y
authors: Tosa
mesh_terms: D000483:Alleles; D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D001483:Base Sequence; D002869:Chromosome Aberrations; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal / Q000235:genetics*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D025282:Mycelium; D012275:Oryza / Q000382:microbiology*; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D014774:Virulence
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D010940:Plant Proteins