Background:The molecular mechanism underlying the regulation of cellulase production by T. reesei is unclear. Results: The absence of sugar transporter Stp1 enhanced cellulase gene induction whereas the absence of Crt1 abolished cellulase gene expression. Conclusion: Crt1 is essential in cellulase gene induction independent of intracellular sugar delivery. Significance: These data shed light on the mechanism by which T. reesei senses and transmits cellulose signal.

Appropriate perception of cellulose outside the cell by transforming it into an intracellular signal ensures the rapid production of cellulases by cellulolytic Hypocrea jecorina. The major extracellular ␤-glucosidase BglI (CEL3a) has been shown to contribute to the efficient induction of cellulase genes. Multiple ␤-glucosidases belonging to glycosyl hydrolase (GH) family 3 and 1, however, exist in H. jecorina. Here we demonstrated that CEL1b, like CEL1a, was an intracellular ␤-glucosidase displaying in vitro transglycosylation activity. We then found evidence that these two major intracellular ␤-glucosidases were involved in the rapid induction of cellulase genes by insoluble cellulose. Deletion of cel1a and cel1b significantly compromised the efficient gene expression of the major cellulase gene, cbh1. Simultaneous absence of BglI, CEL1a, and CEL1b caused the induction of the cellulase gene by cellulose to further deteriorate. The induction defect, however, was not observed with cellobiose. The absence of the three ␤-glucosidases, rather, facilitated the induced synthesis of cellulase on cellobiose. Furthermore, addition of cellobiose restored the productive induction on cellulose in the deletion strains. The results indicate that the three ␤-glucosidases may not participate in transforming cellobiose beyond hydrolysis to provoke cellulase formation in H. jecorina. They may otherwise contribute to the accumulation of cellobiose from cellulose as inducing signals.

Th17 cells and interleukin‐17 (IL‐17) have been found to play an important role in the pathology of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Response to IL‐17, reactive astrocytes accompany with immune cells infiltration and axonal damage in MS/EAE. However, the role and the regulatory mechanism of IL‐17‐activated astrocytes in inflammation and in the EAE process still remain largely unknown. Here, we elucidated that miR‐409‐3p and miR‐1896, as co‐upregulated microRNAs in activated astrocytes and in EAE mice, targeted suppressor of cytokine signaling proteins 3 (SOCS3). Overexpression of miR‐409‐3p or miR‐1896 significantly reduced SOCS3 expression and increased phosphorylation of STAT3 as well as induced the inflammatory cytokines production (IL‐1β, IL‐6, IP‐10, MCP‐1, and KC), CD4+T cells migration and demyelination, in turn aggravating EAE development. Importantly, the effects of co‐overexpression of miR‐409‐3p and miR‐1896 in vitro or in vivo are strongly co‐operative. In contrast, simultaneously silenced miR‐409‐3p and miR‐1896 co‐operatively ameliorates inflammation and demyelination in the central nervous system of EAE mice. Collectively, our findings highlight that miR‐409‐3p and miR‐1896 co‐ordinately promote the production of inflammatory cytokines in reactive astrocytes through the SOCS3/STAT3 pathway and enhance reactive astrocyte‐directed chemotaxis of CD4+T cells, leading to aggravate pathogenesis in EAE mice. Co‐inhibition of miR‐409‐3p and miR‐1896 may be a therapeutic target for treating MS and neuroinflammation.

bLactose (1,4-O-␤-D-galacto-pyranosyl-D-glucose) induces cellulolytic enzymes in Trichoderma reesei and is in fact one of the most important soluble carbon sources used to produce cellulases on an industrial level. The mechanism underlying the induction is, however, not fully understood. In this study, we investigated the cellular functions of the intracellular ␤-glucosidases CEL1a and CEL1b in the induction of cellulase genes by lactose in T. reesei. We demonstrated that while CEL1a and CEL1b were functionally equivalent in mediating the induction, the simultaneous absence of these intracellular ␤-glucosidases abolished cbh1 gene expression on lactose. D-Galactose restored the efficient cellulase gene induction in the ⌬cel1a strain independently of its reductive metabolism, but not in the ⌬cel1a ⌬cel1b strain. A further comparison of the transcriptional responses of the ⌬cel1a ⌬cel1b strain complemented with wild-type CEL1a or a catalytically inactive CEL1a version and the ⌬cel1a strain constitutively expressing CEL1a or the Kluyveromyces lactis ␤-galactosidase LAC4 showed that both the CEL1a protein and its glycoside hydrolytic activity were indispensable for cellulase induction by lactose. We also present evidence that intracellular ␤-glucosidase-mediated lactose induction is further conveyed to XYR1 to ensure the efficiently induced expression of cellulase genes.C ost-effective conversion of plant cell wall-derived polysaccharides holds the potential for production of an environmentally clean and renewable source of energy and platform chemicals (1). Trichoderma reesei (teleomorph Hypocrea jecorina) is well known for its high capacity to secrete large amounts of lignocellulosic enzymes that release fermentable sugars and has thus been developed into one of the most prolific industrial cellulase producers. High-yield production of the bulk of the plant cell walldegrading machinery in T. reesei is, however, dependent on induction by insoluble substrates that include cellulose, hemicellulose, and mixtures of plant polymers. Considering the ease of manipulation and the complication of separating enzymes from insoluble plant cell wall materials, soluble inducing substrates are usually preferred or required (2). Among others, the disaccharide lactose (1,4-O-␤-D-galacto-pyranosyl-D-glucose) is an important and economic soluble carbon source for cellulase production by T. reesei. However, the induced cellulase yields on lactose are usually lower than those on cellulose (3, 4). Understanding the differences in the inducing efficiency and the mode by which lactose triggers cellulase formation would be helpful for improving the performance of industrial strains.In fungi, catabolism of lactose is thought to proceed either by extracellular hydrolysis and subsequent uptake of the resulting sugar monomers or by uptake of the disaccharide followed by intracellular hydrolysis (4). For T. reesei, it has been assumed that lactose metabolism relies on the first strategy, based on several findings, including the absence of appar...

Probiotics might offer an attractive alternative to prevent and control Clostridium difficile (C. difficile) infection (CDI). Limited information is available on the ability of commercially used bifidobacterial strains to inhibit C. difficile. This study examined the anti-clostridial effects of Bifidobacterium longum JDM301, a widely used commercial probiotic strain in China, in vitro and in vivo. In vitro evaluation revealed a significant reduction in C. difficile counts when JDM301 was co-cultured with C. difficile, which was correlated with the significant decrease in clostridial toxin titres (TcdA and TcdB). Furthermore, the cell-free culture supernatants (CFS) of JDM301 inhibited C. difficile growth and degraded TcdA and TcdB. Notably, the results showed that acid pH promoted the degradation of TcdA by CFS from JDM301. Furthermore, comparative studies among 10 B. longum strains were performed, which showed that the inhibitory effect of CFS from JDM301 was similar with the other 8 B. longum strains and higher than strain BLY1. However, when it was neutralized, the significant different was lost. When present together, it was suggested that the acid pH induced by probiotics not only played important roles in the growth inhibition against C. difficile resulting in the reduction of toxins titres, but also directly promoted the degradation of clostridial toxin. In vivo studies proved that JDM301 partially relieved damage to tissues caused by C. difficile and also decreased the number of C. difficile and toxin levels. In summary, our results demonstrated that the commercial strain, JDM301 could be considered a probiotic able to exert anti-toxin capability and most of the CFS from Bifidobacterium were able to inhibit the growth of C. difficile, depending on acid pH. These results highlighted a potential that JDM301 could be helpful in preventing CDI and that most of the bifidobacterial strains could (at least partially) exert protective effects by reducing toxin titres through growth inhibition against toxigenic C. difficile.