Endopolygalacturonase is essential for citrus black rot caused by Alternaria citri but not brown spot caused by Alternaria alternata

Atsunori Isshiki, Kazuya Akimitsu, Mikihiro Yamamoto, Hiroyuki Yamamoto

Research output: Contribution to journalArticle

157 Citations (Scopus)

Abstract

Alternaria citri, the cause of Alternaria black rot, and Alternaria alternata rough lemon pathotype, the cause of Alternaria brown spot, are morphologically indistinguishable pathogens of citrus: one causes rot by macerating tissues and the other causes necrotic spots by producing a host-selective toxin. To evaluate the role of endopolygalacturonase (endoPG) in pathogenicity of these two Alternaria spp. pathogens, their genes for endoPG were mutated by gene targeting. The endoPGs produced by these fungi have similar biochemical properties, and the genes are highly similar (99.6% nucleotide identity). The phenotypes of the mutants, however, are completely different. An endoPG mutant of A. citri was significantly reduced in its ability to cause black rot symptoms on citrus as well as in the maceration of potato tissue and could not colonize citrus peel segments. In contrast, an endoPG mutant of A. alternata was unchanged in pathogenicity. The results indicate that a cell wall-degrading enzyme can play different roles in the pathogenicity of fungal pathogens. The role of a cell wall-degrading enzyme depends upon the type of disease but not the taxonomy of the fungus.

Original languageEnglish
Pages (from-to)749-757
Number of pages9
JournalMolecular Plant-Microbe Interactions
Volume14
Issue number6
DOIs
Publication statusPublished - Jun 2001

Keywords

  • ACR-toxin
  • Host-specific toxin
  • Pectinase

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science

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