Abstract
BackgroundIn the biotechnological workhorse Trichoderma reesei (Hypocrea jecorina) transcription of cellulase genes as well as efficiency of the secreted cellulase mixture are modulated by light. Components of the heterotrimeric G-protein pathway interact with light-dependent signals, rendering this pathway a key regulator of cellulase gene expression.ResultsAs regulators of heterotrimeric G-protein signaling, class I phosducin-like proteins, are assumed to act as co-chaperones for G-protein beta-gamma folding and exert their function in response to light in higher eukaryotes. Our results revealed light responsive transcription of the T. reesei class I phosducin-like protein gene phlp1 and indicate a light dependent function of PhLP1 also in fungi. We showed the functions of PhLP1, GNB1 and GNG1 in the same pathway, with one major output being the regulation of transcription of glycoside hydrolase genes including cellulase genes in T. reesei. We found no direct correlation between the growth rate and global regulation of glycoside hydrolases, which suggests that regulation of growth does not occur only at the level of substrate degradation efficiency.Additionally, PhLP1, GNB1 and GNG1 are all important for proper regulation of light responsiveness during long term exposure. In their absence, the amount of light regulated genes increased from 2.7% in wild type to 14% in Δphlp1. Besides from the regulation of degradative enzymes, PhLP1 was also found to impact on the transcription of genes involved in sexual development, which was in accordance with decreased efficiency of fruiting body formation in Δphlp1. The lack of GNB1 drastically diminished ascospore discharge in T. reesei.ConclusionsThe heterotrimeric G-protein pathway is crucial for the interconnection of nutrient signaling and light response of T. reesei, with the class I phosducin-like protein PhLP1, GNB1 and GNG1 acting as important nodes, which influence light responsiveness, glycoside hydrolase gene transcription and sexual development.
Highlights
In the biotechnological workhorse Trichoderma reesei (Hypocrea jecorina) transcription of cellulase genes as well as efficiency of the secreted cellulase mixture are modulated by light
T. reesei was grown on microcrystalline cellulose for 72 hours in constant light and constant darkness, since the fungus is in its active phase of growth and enzyme production at this time
Transcription of the light regulatory protein encoding env1, the photolyase gene phr1 and the peptide pheromone precursor encoding gene hpp1 correlated with earlier data under similar conditions and confirm that growth conditions were appropriate for our analysis
Summary
In the biotechnological workhorse Trichoderma reesei (Hypocrea jecorina) transcription of cellulase genes as well as efficiency of the secreted cellulase mixture are modulated by light. Light has an effect on almost all metabolic pathways in fungi, such as carotenoid metabolism [4], fatty acid metabolism [5], cAMP levels [6], sulfur metabolism [7] and carbohydrate metabolism [8]. It was reported already more than 40 years ago that consuming. One prominent mechanism for achievement of this task is the heterotrimeric G-protein signaling pathway [16,17], which is interconnected with the light response pathway in Trichoderma reesei [18,19,20,21]
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