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.
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This study was supported by JSPS KAKENHI Grant Number 20248005.
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Comparisons of sexual fertility and mycelial growth between F1-327 and its subcultured strains lacking the 1.6 Mb chromosome (DOCX 32 kb)
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Kusaba, M., Mochida, T., Naridomi, T. et al. 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. Curr Genet 60, 315–325 (2014). https://doi.org/10.1007/s00294-014-0437-y
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DOI: https://doi.org/10.1007/s00294-014-0437-y