Chen, D. - School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China.
Li, G. - School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China.
Liu, J. - Chongqing Key Laboratory of Economic Plant Biotechnology, Collaborative Innovation Centre of Special Plant Industry in Chongqing, College of Forestry and Life Science, Institute of Special Plants, Chongqing University of Arts and Sciences, Yongchuan, 402160, China.
Wisniewski, M. - United States Department of Agriculture-Agricultural Research Service, Kearneysville, WV, United States.
Huang, S. - School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China.
Liu, Y. - School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China; School of Horticulture, Anhui Agricultural University, Hefei, 230036, China; Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
Penicillium expansum is a destructive phytopathogen causing postharvest decay on many stored fruits. To develop effective and safe management strategies, it is important to investigate its pathogenicity-related mechanisms. In this study, a bioinformatic pipeline was constructed and 50 core effector genes were identified in P. expansum using multiple RNA-seq data sets and their putative functions were implicated by comparatively homologous analyses using pathogen–host interaction database. To functionally characterize P. expansum LysM domain proteins during infection, null mutants for the 15 uncharacterized putative LysM effectors were constructed and the fungal growth rate on either PDA or Cazpek medium or lesion expansion rate on the infected apple fruits was evaluated. The results showed the growth rate of knockout mutants from PeLysM5, PeLysM12 and PeLysM15 was retarded on PDA medium. No significant difference in growth rate was observed between wild type and all mutants on solid Cazpek medium. Nevertheless, the hypha of wild type displayed deeper yellow on the back of Cazpek medium than those of knockout mutants. On the infecting apples fruits, the knockout mutants from PeLysM5, PeLysM7, PeLysM8, PeLysM9, PeLysM10, PeLysM11, PeLysM14, PeLysM15, PeLysM16, PeLysM18 and PeLysM19 showed enhanced fungal virulence, with faster decaying on infected fruits than those from wild type. By contrast, the knockout mutation at PeLysM12 locus led to reduced lesion expansion rate on the infected apple fruits. In addition, P. expansum-apple interaction RNA-seq experiment was performed using apple fruit tissues infected by the wild type and knockout mutant ΔPeLysM15, respectively. Transcriptome analyses indicated that deletion of PeLysM15 could activate expression of several core effector genes, such as PEX2_055830, PEX2_036960 and PEX2_108150, and a chitin-binding protein, PEX2_064520. These results suggest PeLysM15 may play pivotal roles in fungal growth and development and involve pathogen–host interaction by modulating other effector genes’ expression. Our results could provide solid data reference and good candidates for further pathogen-related studies in P. expansum.
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