Aspergillus niger, which is a fungal pathogen, causes rot in a variety of fruits. In this study, the cystathionine β-synthase cbsA gene was deleted by homologous recombination to study its role in sulfur metabolism and pathogenicity of A. niger. The results showed that Δ cbsA strain maintained normal mycelia growth and sporulation compared with the control strain A. niger MA 70.15, whereas the contents of cysteine and glutathione (GSH) increased significantly after cbsA deletion. However, Δ cbsA strain showed reduced endogenous H2S production. Further results showed that cbsA gene deletion induced higher resistance to cadmium stress and stronger infectivity to pears. It was also found that a stronger response of reactive oxygen species (ROS) production was induced in Δ cbsA mutant-infected pear compared with the control strain. In all, the present research suggested the important role of cbsA in sulfur metabolism and pathogenicity of A. niger in pear fruit.
Keywords: Aspergillus niger; cadmium stress; cystathionine β-synthase; pathogenicity; sulfur metabolism.