Development of a powerful synthetic hybrid promoter to improve the cellulase system of Trichoderma reesei for efficient saccharification of corncob residues

Abstract Background The filamentous fungus Trichoderma reesei is a widely used workhorse for cellulase production in industry due to its prominent secretion capacity of extracellular cellulolytic enzymes. However, some key components are not always sufficient in this cellulase cocktail, making the conversion of cellulose-based biomass costly on the industrial scale. Development of strong and efficient promoters would enable cellulase cocktail to be optimized for bioconversion of biomass. Results In this study, a synthetic hybrid promoter was constructed and applied to optimize the cellulolytic system of T. reesei for efficient saccharification towards corncob residues. Firstly, a series of 5’ truncated promoters in different lengths were established based on the strong constitutive promoter Pcdna1. The strongest promoter amongst them was Pcdna1-3 (− 640 to − 1 bp upstream of the translation initiation codon ATG), exhibiting a 1.4-fold higher activity than that of the native cdna1 promoter. Meanwhile, the activation region (− 821 to − 622 bp upstream of the translation initiation codon ATG and devoid of the Cre1-binding sites) of the strong inducible promoter Pcbh1 was cloned and identified to be an amplifier in initiating gene expression. Finally, this activation region was fused to the strongest promoter Pcdna1-3, generating the novel synthetic hybrid promoter Pcc. This engineered promoter Pcc drove strong gene expression by displaying 1.6- and 1.8-fold stronger fluorescence intensity than Pcbh1 and Pcdna1 under the inducible condition using egfp as the reporter gene, respectively. Furthermore, Pcc was applied to overexpress the Aspergillus niger β-glucosidase BGLA coding gene bglA and the native endoglucanase EG2 coding gene eg2, achieving 43.5-fold BGL activity and 1.2-fold EG activity increase, respectively. Ultimately, to overcome the defects of the native cellulase system in T. reesei, the bglA and eg2 were co-overexpressed under the control of Pcc promoter. The bglA-eg2 double expression strain QPEB70 exhibited a 178% increase in total cellulase activity, whose cellulase system displayed 2.3- and 2.4-fold higher saccharification efficiency towards acid-pretreated and delignified corncob residues than the parental strain, respectively. Conclusions The synthetic hybrid promoter Pcc was generated and employed to improve the cellulase system of T. reesei by expressing specific components. Therefore, construction of synthetic hybrid promoters would allow particular cellulase genes to be expressed at desired levels, which is a viable strategy to optimize the cellulolytic enzyme system for efficient biomass bioconversion.

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Development of a Powerful Synthetic Hybrid Promoter to Improve the Cellulase System of Trichoderma Reesei for Efficient Saccharification of Corncob Residues

10.21203/rs.3.rs-584234/v1 ◽

2021 ◽

Author(s):

Yifan Wang ◽

Ruiyan Liu ◽

Hong Liu ◽

Xihai Li ◽

Linjing Shen ◽

...

Keyword(s):

Gene Expression ◽

Trichoderma Reesei ◽

Cellulase Activity ◽

Inducible Promoter ◽

Cellulase Production ◽

Cellulolytic Enzymes ◽

Cellulolytic Enzyme ◽

Activity Increase ◽

Hybrid Promoter ◽

Saccharification Efficiency

Abstract Background: The filamentous fungus Trichoderma reesei is a widely used workhorse for cellulase production in industry due to its prominent secretion capacity of extracellular cellulolytic enzymes. However, some key components are not always sufficient in this cellulase cocktail, making the conversion of cellulose-based biomass costly on the industrial scale. Development of strong and efficient promoters would enable cellulase cocktail to be optimized for bioconversion of biomass.Results: In this study, a synthetic hybrid promoter was constructed and applied to optimize the cellulolytic system of T. reesei for efficient saccharification towards corncob residues. Firstly, a promoter library was established by sequence truncation based on the strong constitutive promoter Pcdna1. The strongest promoter amongst them was Pcdna1-3, exhibiting a 1.4-fold higher activity than that of the native cdna1 promoter. Meanwhile, the activation region (-821 to -622 bp upstream of the translation initiation codon ATG and devoid of the Cre1-binding sites) of the strong inducible promoter Pcbh1 was cloned and identified to be an amplifier in initiating gene expression. Finally, this activation region was fused to the strongest promoter Pcdna1-3, generating the novel synthetic hybrid promoter Pcc. This engineered promoter Pcc drove strong gene expression by displaying 1.6- and 1.8-fold stronger fluorescence intensity than Pcbh1 and Pcdna1 under the inducible condition using egfp as the reporter gene, respectively. Furthermore, Pcc was applied to overexpress the Aspergillus niger β-glucosidase BGLA coding gene bglA and the native endoglucanase EG2 coding gene eg2, achieving a 43.5-fold BGL activity and 1.2-fold EG activity increase, respectively. Ultimately, to overcome the defects of the native cellulase system in T. reesei, the bglA and eg2 were co-overexpressed under the control of Pcc promoter. The bglA-eg2 double expression strain QPEB70 exhibited a 178% increase in total cellulase activity, whose cellulase system displayed 2.3- and 2.4-fold higher saccharification efficiency towards acid-pretreated and delignified corncob residues than the parental strain, respectively.Conclusions: The synthetic hybrid promoter Pcc was generated and employed to improve the cellulase system of T. reesei by expressing specific components. Therefore, construction of synthetic hybrid promoters would allow particular cellulase genes to be expressed at desired levels, which is a viable strategy to optimize the cellulolytic enzyme system for efficient biomass bioconversion.

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Loss of the Gata1 Gene IE Exon Leads to Variant Transcript Expression and the Production of GATA1 Protein Lacking the N-Terminal Domain.

Blood ◽

10.1182/blood.v114.22.3648.3648 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3648-3648

Author(s):

Eri Kobayashi ◽

Ritsuko Shimizu ◽

Yuko Kikuchi ◽

Satoru Takahashi ◽

Masayuki Yamamoto

Keyword(s):

Gene Expression ◽

Translation Initiation ◽

Knockout Mice ◽

Conflicts Of Interest ◽

Hematopoietic Cells ◽

Full Length ◽

Initiation Codon ◽

Severe Thrombocytopenia ◽

Exon 2 ◽

Translation Initiation Codon

Abstract Abstract 3648 Poster Board III-584 GATA1 is a transcription factor essential for the differentiation of erythroid cells and megakaryocytes. Since GATA1 regulates genes related to the survival, proliferation and differentiation of hematopoietic cells, regulation of the Gata1 gene expression is critically important for the understanding of hematopoiesis. The Gata1 locus contains multiple untranslated first exons plus five common coding exons. Of these first exons, erythroid first exon (IE exon) is important for the Gata1 gene expression in the hematopoietic lineages. However, due to the embryonic lethality of this IE exon knockdown mice, less is understood about the contribution of the IE exon to adult hematopoiesis. Here, we achieved specific deletion of the IE exon in adulthood by crossing the IE-floxed mice with the interferon-inducible Mx1-Cre transgenic mice. This conditional IE-deletion mouse (ΔIE mouse) showed severe thrombocytopenia with increased premature megakaryocytes similarly to the phenotypes reported in the conditional Gata1 knockout mice in which the entire Gata1 gene was deleted in adulthood. In addition, the ΔIE mice showed severe anemia with skewed erythroid maturation, and importantly this erythroid phenotypes substantially differed from those observed in the conditional Gata1 knockout mice. Further analyses revealed that the Gata1 mRNA level in the megakaryocytic lineage was significantly downregulated. By contrast, in the erythroid lineage, Gata1 mRNA was retained at a comparable level to that in control mice utilizing two alternative first exons; one was the IEb/c, which was previously reported as a first exon rarely used in hematopoietic cells, and the other was newly identified IEd exon located within the second intron. Surprisingly, in the ΔIE mice these transcripts failed to produce full-length GATA1 protein, but instead inefficiently yielded GATA1 lacking the N-terminal 83 amino acids. This form of GATA1 is often observed in Down syndrome-associated transient myeloproliferative disorder and acute megakaryoblastic leukemia. Of note, the transcript derived from exon IEb/c preserved the first translation initiation codon in exon 2 but lost the potential to select the first translation initiation codon or failed to produce full-length GATA1. The present study demonstrates that the IE exon is instrumental to adult erythropoiesis by regulating the proper level of transcription and by selecting the correct translation start site for production of adequate full-length GATA1 protein. Disclosures: No relevant conflicts of interest to declare.

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