The Cerato-Platanin EPL2 from Trichoderma reesei Is Not Directly Involved in Cellulase Formation but in Cell Wall Remodeling.

Trichoderma reesei is a saprophytic fungus that produces large amounts of cellulases and is widely used for biotechnological applications. Cerato-platanins (CPs) are a family of proteins universally distributed among Dikarya fungi and have been implicated in various functions related to fungal physiology and interaction with the environment. In T. reesei , three CPs are encoded in the genome: Trire2_111449 , Trire2_123955, and Trire2_82662 . However, their function is not fully elucidated. In this study, we deleted the Trire2_123955 gene (named here as epl2 ) in the wild-type QM6aΔ tmus53 Δ pyr4 (WT) strain and examined the behavior of the Δ epl2 strain compared with WT grown for 72 h in 1% cellulose using RNA sequencing. Of the 9143 genes in the T. reesei genome, 760 were differentially expressed, including 260 only in WT, 214 only in Δ epl2 , and 286 in both. Genes involved in oxidative stress, oxidoreductase activity, antioxidant activity, and transport were upregulated in the Δ epl2 mutant. Genes encoding cell wall synthesis were upregulated in the mutant strain during the late growth stage. The Δ epl2 mutant accumulated chitin and glucan at higher levels than the parental strain and was more resistant to cell wall stressors. These results suggest a compensatory effect in cell wall remodeling due to the absence of EPL2 in T. reesei . This study is expected to contribute to a better understanding of the role of the EPL2 protein in T. reesei and improve its application in biotechnological fields.