Cloning and characterization of a novel chitinase gene (chi46) from Chaetomium globosum and identification of its biological activity.

Chitinases play a major role in the defensive strategies of plants against fungal pathogens. In the current study, the gene for a 46-kDa endochitinase (chi46) was cloned from Chaetomium globosum, an important biocontrol fungus. The corresponding complementary deoxyribonucleic acid sequence was 1,350 bp in length, encoding 449 amino acid residues. The temporal expression of chi46, in response to the treatments of cell walls of six pathogens and confrontation against two fungal pathogens, was measured in C. globosum using real-time reverse transcription polymerase chain reaction. The expression of chi46 can be highly induced by exposure to the cell walls of plant pathogens and living pathogens, suggesting a role in plant disease resistance. The chi46 gene was inserted into the pPIC9 vector and transferred into the cells of Pichia pastoris GS115 for heterologous expression. The optimal reaction conditions for chitinase CHI46 activity were: 45 degrees C, pH of 5.0, and 5 mmol l(-1) of Cu2+. The maximum enzyme activity was 1.42 U ml(-1) following exposure to the cell wall chitin of Septoria tritici. The CHI46 enzyme can efficiently degrade cell walls of the phytopathogenic Rhizoctonia solani, Fusarium oxysporum, Sclerotinia sclerotiorum, Valsa sordida, S. tritici, and Phytophthora sojae, demonstrating that it may be involved in the biocontrol mechanism of C. globosum.