Comparative analysis of the Trichoderma reeseitranscriptome during growth on the cellulase inducing substrates wheat straw and lactose

Abstract

BackgroundRenewable lignocellulosic biomass is an advantageous resource for the production of second generation biofuels and other biorefinery products. In Middle Europe, wheat straw is one of the most abundant low-cost sources of lignocellulosic biomass. For its efficient use, an efficient mix of cellulases and hemicellulases is required. In this paper, we investigated how cellulase production by T. reesei on wheat straw compares to that on lactose, the only soluble and also cheap inducing carbon source for enzyme production.ResultsWe have examined and compared the transcriptome of T. reesei growing on wheat straw and lactose as carbon sources under otherwise similar conditions. Gene expression on wheat straw exceeded that on lactose, and 1619 genes were found to be only induced on wheat straw but not on lactose. They comprised 30% of the CAZome, but were also enriched in genes associated with phospholipid metabolism, DNA synthesis and repair, iron homeostatis and autophagy. Two thirds of the CAZome was expressed both on wheat straw as well as on lactose, but 60% of it at least >2-fold higher on the former. Major wheat straw specific genes comprised xylanases, chitinases and mannosidases. Interestingly, the latter two CAZyme families were significantly higher expressed in a strain in which xyr1 encoding the major regulator of cellulase and hemicellulase biosynthesis is non-functional.ConclusionsOur data reveal several major differences in the transcriptome between wheat straw and lactose which may be related to the higher enzyme formation on the former and their further investigation could lead to the development of methods for increasing enzyme production on lactose.

WITHDRAWN: Identification of an endogenous redox partner for lytic polysaccharide monooxygenase-based oxidative cleavage of polysaccharides

“…For gene-specific qRT-PCR, primer pairs were designed with an amplicon size of 150bp ( Table 5). The Actin rRNA housekeeping gene was used as a reference gene (44). Each 20-µl qRT-PCR mixture contained 10 µl of Power SYBR green master mix (Applied Biosystems Inc. CA, USA), 1 µl of cDNA, and 1 µl each of 2.5 μM forward and reverse primers.…”

Transcriptomic Profile of Lignocellulose Degradation from Trametes versicolor on Poplar Wood

“…It could also be useful for the production of second-generation bioethanol or for the decoloration, decontamination, and degradation of other macromolecular compounds (Patt et al2006;Alexieva et al2010;Bischof et al 2013;Nguyen et al 2014). T. versicolor is a common fungi species native to temperate climate zones that can secrete PODs, laccases, and carbohydrate-active enzymes.…”

Transcriptional Regulation and Responses in Filamentous Fungi Exposed to Lignocellulose

“…Genes involved in asexual sporulation and autolytic cell wall recycling were induced in A. niger after exposure to wheat straw for 24 hours, suggesting the fungus indeed experiences carbon limitation or starvation when growing on wheat straw [42]. Also in T. reesei grown on wheat straw, autophagy was induced and cell wall remodelling enzymes were up-regulated [121], indicating nutrient limitation. With regard to iron limitation, growth in the presence of lignocellulose can lead to stress due to lack of available iron.…”

“…Wheat straw binds iron thereby decreasing its availability to the fungus. Furthermore, iron consumption by T. reesei is ~ 3-fold higher on wheat straw compared to growth on lactose [121]. In response to the iron limitation, growth of T. reesei on wheat straw was accompanied by increased expression of genes encoding proteins involved in iron transport, siderophore transporters and siderophore biosynthesis as well as ferric reductases [121].…”

“…Most of the relevant transporters are sugar transporters belonging to the major facilitator superfamily (MFS) which includes hexose and pentose sugar and short oligosaccharide transporters [120]. Other relevant transporters include those involved in iron homeostasis which were induced on lignocellulose in T. reesei [121]. The transporter classification database (www.tcdb.org/) provides an extensive classification system for transporters [122].…”