Expression analysis of the α-1,2-mannosidase from the mycoparasitic fungus Trichoderma harzianum

A range of hydrolytic enzymes are involved in mycoparasitism, including chitinases, β-glucanases and proteases. Recent studies of Trichoderma harzianum interaction with certain phytopathogens have shown that other enzymes may also be involved in this mechanism, among them α-1,2-mannosidases. These enzymes play an essential role in glycoprotein recycling in filamentous fungi, but nothing is known about their role in mycoparasitism. The aim of this work was to study the expression of the α-1,2-mannosidase gene from T. harzianum (Th) after growth on cell walls of Sclerotinia sclerotiorum (CWSS), Fusarium solani (CWFS) and Fusarium oxysporum (CWFO). The expression of this gene was also analyzed during the interaction between T. harzianum and these phytopathogens in dual culture. A significant increase in expression was observed when T. harzianum was grown in the presence of CWSS (4.5-fold), CWFS (18-fold) and CWFO (75-fold), compared to the control. In dual culture experiments a marked upregulation (58-fold) was observed during Th x F. oxysporum confrontation. These data suggest that the composition of the cell wall of F. oxysporum is an important inducer of expression of the α-1,2-mannosidases gene from T. harzianum.