Abstract
We defined the role of the transcriptional factor—XYR1—in the filamentous fungus Trichoderma reesei during cellulosic material degradation. In this regard, we performed a global transcriptome analysis using RNA-Seq of the Δxyr1 mutant strain of T. reesei compared with the parental strain QM9414 grown in the presence of cellulose, sophorose, and glucose as sole carbon sources. We found that 5885 genes were expressed differentially under the three tested carbon sources. Of these, 322 genes were upregulated in the presence of cellulose, while 367 and 188 were upregulated in sophorose and glucose, respectively. With respect to genes under the direct regulation of XYR1, 30 and 33 are exclusive to cellulose and sophorose, respectively. The most modulated genes in the Δxyr1 belong to Carbohydrate-Active Enzymes (CAZymes), transcription factors, and transporters families. Moreover, we highlight the downregulation of transporters belonging to the MFS and ABC transporter families. Of these, MFS members were mostly downregulated in the presence of cellulose. In sophorose and glucose, the expression of these transporters was mainly upregulated. Our results revealed that MFS and ABC transporters could be new players in cellulose degradation and their role was shown to be carbon source-dependent. Our findings contribute to a better understanding of the regulatory mechanisms of XYR1 to control cellulase gene expression in T. reesei in the presence of cellulosic material, thereby potentially enhancing its application in several biotechnology fields.
Highlights
Our dependence on fossil fuels and concerns surrounding its impacts on the environment has generated worldwide interest in establishing new fuel and energy sources (Borin et al, 2015)
T. reesei QM9414 and the mutant strain ∆xyr1 were cultivated in cellulose, sophorose, and glucose as unique carbon sources (Figure S1) and three biological replicates of each condition were submitted for RNA sequencing using Illumina HiseqTM 2000
The quality of data generated in sequencing was evaluated by the DESeq2 package and a high Pearson correlation was obtained when comparing the corresponding replicates of QM9414 (R ≥ 0.71) and ∆xyr1 (R ≥ 0.67) for the three studied conditions (Figures S2, S3)
Summary
Our dependence on fossil fuels and concerns surrounding its impacts on the environment has generated worldwide interest in establishing new fuel and energy sources (Borin et al, 2015). Reduction in fossil fuel consumption using alternate energy sources is a major challenge that humankind will face in the coming decades. Bioethanol production using lignocellulosic biomass, is a viable option for addressing this challenge (Ulaganathan et al, 2015). Lignocellulosic biomass is among the most abundant renewable resources on the planet and is an alternative. Frontiers in Microbiology | www.frontiersin.org dos Santos Castro et al. The Role of the Master Regulator “XYR1” in Trichoderma reesei sustainable energy source for the production of secondgeneration biofuels. Simple or complex carbohydrates can be extracted from lignocellulosic biomass that is fermented by microorganisms during bioethanol production (Kricka et al, 2015)
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