Abstract
Trichoderma harzianum, whose gene expression is tightly controlled by the transcription factors (TFs) XYR1 and CRE1, is a potential candidate for hydrolytic enzyme production. Here, we performed a network analysis of T. harzianum IOC-3844 and T. harzianum CBMAI-0179 to explore how the regulation of these TFs varies between these strains. In addition, we explored the evolutionary relationships of XYR1 and CRE1 protein sequences among Trichoderma spp. The results of the T. harzianum strains were compared with those of Trichoderma atroviride CBMAI-0020, a mycoparasitic species. Although transcripts encoding carbohydrate-active enzymes (CAZymes), TFs, transporters, and proteins with unknown functions were coexpressed with cre1 or xyr1, other proteins indirectly related to cellulose degradation were identified. The enriched GO terms describing the transcripts of these groups differed across all strains, and several metabolic pathways with high similarity between both regulators but strain-specific differences were identified. In addition, the CRE1 and XYR1 subnetworks presented different topology profiles in each strain, likely indicating differences in the influences of these regulators according to the fungi. The hubs of the cre1 and xyr1 groups included transcripts not yet characterized or described as being related to cellulose degradation. The first-neighbor analyses confirmed the results of the profile of the coexpressed transcripts in cre1 and xyr1. The analyses of the shortest paths revealed that CAZymes upregulated under cellulose degradation conditions are most closely related to both regulators, and new targets between such signaling pathways were discovered. Although the evaluated T. harzianum strains are phylogenetically close and their amino acid sequences related to XYR1 and CRE1 are very similar, the set of transcripts related to xyr1 and cre1 differed, suggesting that each T. harzianum strain used a specific regulation strategy for cellulose degradation. More interestingly, our findings may suggest that XYR1 and CRE1 indirectly regulate genes encoding proteins related to cellulose degradation in the evaluated T. harzianum strains. We believe that our findings are important for expanding the use of T. harzianum as an enzyme producer in biotechnological industrial applications and pave the way for further studies evaluating differences across strains of the same species.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- ABC
- ATP-binding cassette
- CAZymes
- carbohydrate-active enzymes
- CCR
- carbon catabolite repression
- CEs
- carbohydrate esterases
- CRE1
- carbon catabolite repressor 1
- GHs
- glycoside hydrolases
- GO
- Gene Ontology
- GTs
- glycosyltransferases
- HRR
- highest reciprocal rank
- iTOL
- Interactive Tree of Life
- ITS
- internal transcribed spacer
- JTT
- Jones-Taylor-Thornton
- K2P
- Kimura two-parameter
- KEGG
- Kyoto Encyclopedia of Genes and Genomes
- KO
- KEGG Orthology
- MEGA
- Molecular Evolutionary Genetics Analysis
- MFS
- major facilitator superfamily
- ML
- Maximum likelihood
- PLs
- polysaccharide lyases
- Ta0020
- Trichoderma atroviride CBMAI-0020
- tef1
- translational elongation factor 1
- TFs
- transcription factors
- Th0179
- Trichoderma harzianum CBMAI-0179
- Th3844
- Trichoderma harzianum IOC-3844
- TOM
- topological overlap matrix
- TPM
- transcripts per million
- WGCNA
- weighted correlation network analysis
- XYR1
- xylanase regulator 1