The β‐N‐acetylglucosaminidases NAG1 and NAG2 are essential for growth of Trichoderma atroviride on chitin

Abstract

The chitinolytic enzyme machinery of fungi consists of chitinases and β‐N‐acetylglucosaminidases. These enzymes are important during the fungal life cycle for degradation of exogenous chitin, which is the second most abundant biopolymer, as well as fungal cell‐wall remodelling. In addition, involvement of chitinolytic enzymes in the lysis of the host cell wall in mycoparasitic Trichoderma spp. has been reported. In view of the fact that fungi have on average 15–20 chitinases, but only two β‐N‐acetylglucosaminidases, the question arises how important the latter enzymes actually are for various aspects of chitin degradation. In this study, the role of two β‐N‐acetylglucosaminidases, NAG1 and NAG2, was analysed in the mycoparasitic fungus Trichoderma atroviride. No β‐N‐acetylglucosaminidase activity was detected in T. atrovirideΔnag1Δnag2 strains, suggesting that NAG1 and NAG2 are the only enzymes in T. atroviride that possess this activity. Δnag1Δnag2 strains were not able to grow on chitin and chitobiose, but the presence of either NAG1 or NAG2 was sufficient to restore growth on chitinous carbon sources in solid media. Our results demonstrated that T. atroviride cannot metabolize chitobiose but only the monomer N‐acetylglucosamine, and that N‐acetylglucosaminidases are therefore essential for the use of chitin as a nutrient source. NAG1 is predominantly secreted into the medium, whereas NAG2 mainly remains attached to the cell wall. No physiological changes or reduction of the mycoparasitic potential of T. atroviride was detected in the double knockout strains, suggesting that the use of chitin as carbon source is only of minor importance for these processes.

RNA Interference of Endochitinases in the Sugarcane Endophyte Trichoderma virens 223 Reduces Its Fitness as a Biocontrol Agent of Pineapple Disease

“…The dispensable role of N- acetyl-ß-D-glucosaminidase to biocontrol activity was proposed previously [16] and our work supports this suggestion. Our findings are also consistent with a recent study by [59] that showed that the biocontrol efficacy of T. atroviride was unaffected by single and double deletions of the nag1 and nag2 genes.…”

Self-assembly at Air/Water Interfaces and Carbohydrate Binding Properties of the Small Secreted Protein EPL1 from the fungus Trichoderma atroviride

“…Growth on chitin was tested in static liquid cultivations with SM medium, 1% chitin, and 0.1% peptone (27) and on the same medium in agar plates solidified with 1.5% agar with and without peptone. Biomass measurements from liquid cultivations and assessment of sporulation rates on agar plates were carried out as described (31). Furthermore, hydrophobicity of the mycelium was assessed by pipetting water droplets on the mycelium as has been described previously for Trichoderma reesei hydrophobin knock-out strains (32).…”

Chitinase Expression Due to Reduction in Fusaric Acid Level in an Antagonistic Trichoderma harzianum S17TH

“…Since expression of the chitinase genes, chi42 [17] and nag1 [18], have been demonstrated to contribute to disease suppression in Trichoderma, their expression during reduction in FA level was analyzed using the RNA samples. While ech42 expression was slightly repressed at 400 ppm of FA, nag1 was significantly repressed at 300 ppm.…”