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Rapid evolution of avirulence genes in rice blast fungus Magnaporthe oryzae

Ju Huang, Weina Si, Qiming Deng

  • 1State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, China. liping6575@163.com.

BMC Genetics
|April 15, 2014
PubMed
Abstract

Insights

Avirulence (Avr) genes in rice blast fungus rapidly evolve through gene gain/loss and nucleotide variation, driving pathogen virulence. These evolutionary patterns help identify new Avr-genes and differentiate fungal strains.

Area of Science:

  • Plant Pathology
  • Molecular Evolution
  • Genetics

Background:

  • Magnaporthe oryzae causes devastating rice blast disease.
  • Avirulence (Avr) genes in M. oryzae interact with rice resistance (R) genes.
  • Evolutionary dynamics of Avr-genes in M. oryzae remain largely unexplored.

Purpose of the Study:

  • Investigate genetic variations in Avr-genes.
  • Understand evolutionary patterns of Avr-genes in rice blast fungus.
  • Identify potential indicators for new Avr-genes and strain differentiation.

Main Methods:

  • Analyzed six characterized Avr-genes and seven non-Avr control genes.
  • Studied genetic variation in 62 rice blast strains from China.
  • Assessed nucleotide variation, substitution ratios, and gene presence/absence.

Main Results:

  • Avr-genes exhibited frequent presence/absence polymorphisms and ~10-fold higher nucleotide variation than non-Avr genes.
  • High non-synonymous to synonymous substitution ratios and shared non-synonymous substitutions were observed.
  • Avr-genes were often associated with diverse repeated sequences, explaining polymorphisms.

Conclusions:

  • Frequent Avr-gene deletion/gain and rapid non-synonymous variations drive pathogen adaptation and virulence.
  • These evolutionary features can serve as indicators for identifying novel Avr-genes.
  • High nucleotide polymorphism levels aid in distinguishing genetic groups among M. oryzae strains.

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