The effects of disruption of phosphoglucose isomerase gene on carbon utilisation and cellulase production in Trichoderma reesei Rut-C30

Abstract

BackgroundCellulase and hemicellulase genes in the fungus Trichoderma reesei are repressed by glucose and induced by lactose. Regulation of the cellulase genes is mediated by the repressor CRE1 and the activator XYR1. T. reesei strain Rut-C30 is a hypercellulolytic mutant, obtained from the natural strain QM6a, that has a truncated version of the catabolite repressor gene, cre1. It has been previously shown that bacterial mutants lacking phosphoglucose isomerase (PGI) produce more nucleotide precursors and amino acids. PGI catalyzes the second step of glycolysis, the formation of fructose-6-P from glucose-6-P.ResultsWe deleted the gene pgi1, encoding PGI, in the T. reesei strain Rut-C30 and we introduced the cre1 gene in a Δpgi1 mutant. Both Δpgi1 and cre1+Δpgi1 mutants showed a pellet-like and growth as well as morphological alterations compared with Rut-C30. None of the mutants grew in media with fructose, galactose, xylose, glycerol or lactose but they grew in media with glucose, with fructose and glucose, with galactose and fructose or with lactose and fructose. No growth was observed in media with xylose and glucose. On glucose, Δpgi1 and cre1+Δpgi1 mutants showed higher cellulase activity than Rut-C30 and QM6a, respectively. But in media with lactose, none of the mutants improved the production of the reference strains. The increase in the activity did not correlate with the expression of mRNA of the xylanase regulator gene, xyr1. Δpgi1 mutants were also affected in the extracellular β-galactosidase activity. Levels of mRNA of the glucose 6-phosphate dehydrogenase did not increase in Δpgi1 during growth on glucose.ConclusionsThe ability to grow in media with glucose as the sole carbon source indicated that Trichoderma Δpgi1 mutants were able to use the pentose phosphate pathway. But, they did not increase the expression of gpdh. Morphological characteristics were the result of the pgi1 deletion. Deletion of pgi1 in Rut-C30 increased cellulase production, but only under repressing conditions. This increase resulted partly from the deletion itself and partly from a genetic interaction with the cre1-1 mutation. The lower cellulase activity of these mutants in media with lactose could be attributed to a reduced ability to hydrolyse this sugar but not to an effect on the expression of xyr1.

VIB1, a Link between Glucose Signaling and Carbon Catabolite Repression, Is Essential for Plant Cell Wall Degradation by Neurospora crassa

“…In the hyper-secreting T. reesei strain, RUT-C30, disruption of phosphoglucose isomerase gene ( pgi1 ) blocks formation of fructose-6-P from glucose-6-P and increased cellulase production on glucose. This increase relies on a genetic interaction between the Δ pgi1 mutation and the cre1-1-1 mutation in the RUT-C30 background [62] . Interestingly, both the hyper-secreting T. reesei RUT-C30 and PC-3-7 strains have mutations in cre1 and bglR/col-26 [15] , [63] , [64] , but whether a synergy exists between Δ cre1 and Δ bglR in T. reesei , as in N. crassa , and its relationship to T. reesei vib1 is unclear.…”

Analysis of al-2 Mutations in Neurospora

“…RT-PCR mixtures are detailed in Limón et al [39] . RT-PCRs were performed in an ABI 7500 (Applied Biosystems, Foster City, CA, USA) using a PCR program described by Estrada et al [13] .…”

Cellulase production from kraft hardwood pulp by Trichoderma reesei rut C‐30

“…The filamentous fungus Trichoderma reesei Rut‐C30 is most widely used for the production of cellulolytic and hemicellulolytic enzymes and has become a paradigm for research on these enzymes . Trichoderma reesei could produce a number of extracellular enzymes; however, enzyme production by T. reesei is inducer dependent.…”