The putative protein methyltransferase LAE1 controls cellulase gene expression in Trichoderma reesei

Abstract

Summary Trichoderma reesei is an industrial producer of enzymes that degrade lignocellulosic polysaccharides to soluble monomers, which can be fermented to biofuels. Here we show that the expression of genes for lignocellulose degradation are controlled by the orthologous T. reesei protein methyltransferase LAE1. In a lae1 deletion mutant we observed a complete loss of expression of all seven cellulases, auxiliary factors for cellulose degradation, β-glucosidases and xylanases were no longer expressed. Conversely, enhanced expression of lae1 resulted in significantly increased cellulase gene transcription. Lae1-modulated cellulase gene expression was dependent on the function of the general cellulase regulator XYR1, but also xyr1 expression was LAE1-dependent. LAE1 was also essential for conidiation of T. reesei. Chromatin immunoprecipitation followed by high-throughput sequencing (“ChIP-seq”) showed that lae1 expression was not obviously correlated with H3K4 di- or trimethylation (indicative of active transcription) or H3K9 trimethylation (typical for heterochromatin regions) in CAZyme coding regions, suggesting that LAE1 does not affect CAZyme gene expression by directly modulating H3K4 or H3K9 methylation. Our data demonstrate that the putative protein methyltransferase LAE1 is essential for cellulase gene expression in T. reesei through mechanisms that remain to be identified.

Quantitative proteomics reveals the mechanism and consequence of gliotoxin-mediated dysregulation of the methionine cycle in Aspergillus niger

“…In Trichoderma reesei, LAE1 (A. nidulans LaeA ortholog) has been shown to regulate the expression of genes involved in lignocellulose degradation whereby in a lae1 deletion mutant, a number of cellulases and xylanases were no longer expressed. Additionally, XYR1, the cellulase and hemicellulase transcriptional regulator, was shown to be dependent on LaeA and vice versa [58]. The deletion of vel1, which is the T. reesei ortholog of A. nidulans veA, also diminished the expression of xylanases, cellulases and XYR1 when grown on lactose [59].…”

Trichoderma Research in the Genome Era

“…The T. virens veA ortholog vel1 is involved in regulation of gliotoxin biosynthesis and many other secondary metabolism-related genes, including polyketide synthases (PKSs), NRP synthetases (NRPSs), and methyl transferases, as well as conidiation, hydrophobicity, mycoparasitism, and biocontrol. The T. reesei ortholog (LAE1) of the Aspergillus protein methyltransferase LaeA regulates genes for lignocellulose degradation and secondary metabolism, among others (63,119).…”

Transcription factor Xpp1 is a switch between primary and secondary fungal metabolism

“…The industrially used, cellulase-producing fungus T. reesei secretes a typical yellow pigment on a range of carbon sources (35)(36)(37). The pigment is a mixture of different sorbicillin derivatives, of which biosynthesis results from a gene cluster that is present in a range of not closely related ascomycetes (38,39).…”

“…The global carbon assimilation profiles were evaluated by using Biolog FF MicroPlate (Biolog, Inc.) following a previously described protocol (51), with minor modifications as follows: the inoculum was prepared from cultures on MEX plates incubated at 30°C; mycelial growth was measured after 18,24,30,36,42,48,66,72, and 90 h using biological triplicates.…”