Expression of extracellular peroxidases and catalases in mesophilic and thermophilic Chaetomia in response to environmental oxidative stress stimuli

Abstract

Peroxidases and catalases are well-known antioxidant enzymes produced in almost all living organisms for the elimination of reactive oxygen species (ROS) and thus they prevent the occurrence of oxidative stress. In our study we focused on two soil fungi of the family Chaetomiaceae (mesophilic Chaetomium cochliodes and its thermophilic counterpart C. thermophilum var. dissitum) in order to explore the presence of peroxidase and catalase genes, formation of their native transcripts and protective effect of corresponding translation products in a case study. Predicted genes of our interest were confirmed by genomic PCR and their inducible transcripts by RT-PCR. We were able to quantify the expression levels of newly discovered fungal heme peroxidases and catalases with the reverse-transcription quantitative real-time PCR method. We compared obtained quantitative levels of mRNA production with the level of corresponding extracellular protein occurrence as detected with monitoring their specific peroxidase and catalase activities directly in the cultivation media at optimal growth temperatures. The presence of secretory Catalase 2 from C. thermophilum var. dissitum was detected and identified with mass spectrometry approach directly in the growth medium. This unique catalase is phylogenetically closely related with a previously described catalase-phenol oxidase thus representing an effective and versatile antioxidant in the environment of the fungal mycelia also involved in the catabolism of recalcitrant phenolic substances.

Keywords: Catalases; Chaetomiaceae; Oxidative stress; Peroxidases; Real-time quantitative PCR; Thermophiles.