CRZ1 regulator and calcium cooperatively modulate holocellulases gene expression in Trichoderma reesei QM6a

Abstract

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p><jats:italic>Trichoderma reesei</jats:italic> is the main filamentous fungus used in industry to produce cellulases. Over the last decades, there have been a strong increase in the understanding of the regulatory network controlling cellulase-coding gene expression in response to a number of inducers and environmental signals. In this sense, the role of calcium and the Calcineurin-responsive protein (CRZ1) has been investigated in industrially relevant strains of <jats:italic>T. reesei</jats:italic> RUT-C30, but this system has not been investigated in wild-type reference strain of this fungus.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Here, we investigated the role of CRZ1 and Ca<jats:sup>2+</jats:sup> signaling in the fungus <jats:italic>T. reesei</jats:italic> QM6a. For this, we first searched for potential CRZ1 binding sites in promoter regions of key genes coding holocellulases, as well as transcriptional regulators and sugar and calcium transporters. Using a nearly constructed <jats:italic>T. reesei</jats:italic> Δ<jats:italic>crzl</jats:italic> strain, we demonstrated that most of the genes expected to be regulated by CRZ1 were affected in the mutant strain induced with sugarcane bagasse (SCB) and cellulose. In particular, our data demonstrate that Ca<jats:sup>2+</jats:sup> acts synergistically with CRZ1 to modulate gene expression, but also exerts CRZ1-independent regulatory role in gene expression in <jats:italic>T. reesei</jats:italic>, suggesting the existence of additional Ca<jats:sup>2+</jats:sup> sensing mechanisms in this fungus.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>This work presents new evidence on the regulatory role of CRZ1 and Ca<jats:sup>2+</jats:sup> sensing in the regulation of cellulolytic enzymes in <jats:italic>T. reesei</jats:italic>, evidencing significant and previously unknown function of this Ca<jats:sup>2+</jats:sup> sensing system in the control key transcriptional regulators (XYR1 and CRE1) and on the expression of genes related to sugar and Ca<jats:sup>2+</jats:sup> transport. Taken together, the data obtained here provide new evidence on the regulatory network of <jats:italic>T. reesei</jats:italic> related to plant biomass deconstruction.</jats:p></jats:sec>

Induction of cellulase production by Sr2+ in Trichoderma reesei via calcium signaling transduction

“…Increased concentrations of the second messenger Ca 2+ in the cytosol lead to a response in the downstream calcium pathway (Li et al 2019;Liu et al 2019). Crz1, a critical activator of the calcium signal transduction terminal, plays an essential role in calcium signal transduction pathways (Chen et al 2016;Martins-Santana et al 2020). The transcription level of the transcriptional regulator crz1 detected using RT-qPCR was upregulated after Sr 2+ induction (Fig.…”

“…The intracellular calcium signaling components include free Ca 2+ , calmodulin (CaM), calcineurin (CnA), and calcineurin-responsive zinc finger transcription factor 1 (Crz1) (Bootman et al 2002). Increases in cytosolic Ca 2+ levels lead to the activation of Crz1 via Ca 2+ /CaM/ CnA, which activates downstream genes with different functions by binding to their promoter regions (Martins-Santana et al 2020). Chen et al (2016) reported that the cytosolic Ca 2+ concentration activates the binding of the transcription factor Crz1 to the cellulase gene cbh1 and main transcriptional activator of cellulase genes xyr1, thereby upregulating cellulase gene expression.…”

Mechanistic insights into the role of Ca2+-stimulated AMPK in the secretion of cellulases during carbon stress

“…Similar to archetypical GAL4 transcription factor in yeast, CLR-1, CLR-2, and XYR1 are members of the Zn(II) 2 Cys 6 family of transcription factors having binuclear Zn-Cys binuclear cluster-type DNA-binding domain and activators of genes of secondary carbon sources. Beside these, homologs of ACE3, BGL-R, CRZ1, VIB1, etc., have also been identified as transcriptional activators of lignocellulase in filamentous fungi 15,[18][19][20][21] .…”