Molecular cloning and sequence analysis of the cellobiohydrolase I gene from Trichoderma koningii G-39

Cloning, sequencing and expression analysis of the first cellulase gene encoding cellobiohydrolase 1 from a cold-adaptive Penicillium chrysogenum FS010

A cellobiohydrolase 1 gene (cbh1) was cloned from Penicillium chrysogenum FS010 by a modified thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR). DNA sequencing shows that cbh1 has an open reading frame of 1590 bp, encoding a putative protein of 529 amino acid residues. The deduced amino acid sequence revealed that CBHI has a modular structure with a predicted molecular mass of 56 kDa and consists of a fungal type carbohydrate binding module separated from a catalytic domain by a threonine rich linker region. The putative gene product is homologous to fungal cellobiohydrolases in Family 7 of the glycosyl hydrolases. A novel cbh1 promoter (1.3 kb) was also cloned and sequenced, which contains seven putative binding sites (5'-SYGGRG-3') for the carbon catabolite repressor CRE1. Effect of various carbon sources to the cbh1 transcription of P. chrysogenum was examined by Northern analysis, suggesting that the expression of cbh1 is regulated at transcriptional level. The cbh1 gene in cold-adaptive fungus P. chysogenum was expressed as an active enzyme in Saccharomyces cerevisiae H158. The recombinant CBHI accumulated intracellularly and could not be secreted into the medium.

The effect of self-designed bifunctional RGD-containing fusion protein on the behavior of human keratinocytes and dermal fibroblasts

In this study, self-designed bifunctional RGD-containing fusion protein (BFP) was grafted on the petri dish to evaluate its cytotoxicity and attachment efficiency on primary cultured keratinocytes and dermal fibroblasts. Two lengths of the GRGDS sequences were separately fused to the N-terminus and C-terminus of the Trichoderma koningii cellobiohydrolase I gene cellulose-binding domain, to serve as linking molecule between the cell and the substrate. The grafting procedure was no more labor-intensive and could be done just in aqueous condition itself. The epidermal keratinocytes and dermal fibroblasts, harvested and separated from human foreskin, were cultured in serum-free keratinocyte culture medium and DMEM, respectively. The BFP was dissolved in double-deionized water, and was prepared at different concentrations. The BFP solution was subsequently added into the petri dish for grafting. MTT assay, total DNA measurement, and lactate dehydrogenase analysis were used to evaluate the cell viability, cell proliferation, and cytotoxicity. The immunochemical stain and SEM examination were chosen to make sure that the cultured cells still kept in phenotype. The results showed that the self-designed BFP was successfully coated on the petri dish to improve the cells' adhesion. The whole coating procedure was just done in aqueous solution without any organic solvent being involved. This method was much simpler than the traditional one, and there was no possibility to damage the immobilized biomolecules. From the results of the study, BFP could enhance attachment of keratinocytes and dermal fibroblasts without losing normal cell morphology and keep keratinocytes on the desired differentiation pathway. We believe that coating BFP on petri dish not only enhanced the keratinocyte attachment but also promoted keratinocytes proliferation. We suggest that the self-designed BFP has a great potential to apply on surface modification for the tissue-engineering scaffolds in the future.

Reidentification of cellulolytic enzyme-producing Trichoderma strains W-10 and G-39

Strain W-10, originally identified as Trichoderma koningii, and its supposed mutant G-39, published for production and gene expression of cellulase and xylanase, demonstrated morphological characteristics distinct from those of T. koningii, respectively. To clarify the identification derived from morphological characteristics, several methods were used, including electrophoretic karyotyping, internal transcribed spacer (ITS) analysis of rDNA, and polymerase chain reaction (PCR) fingerprinting using the universal primer L45. All the molecular characteristics showed that strains G-39 and W-10 were identical to T. reesei and T. longibrachiatum, respectively. The results strongly supported that T. koningii G-39 and W-10 should be reassigned as T. reesei and T. longibrachiatum, respectively. Strain G-39 should be considered a mutant from T. reesei QM9414 whose spores were contaminated with those of strain W-10 during a laboratory operation. According to this, we declare that T. koningii G-39 and W-10 must be renamed as T. reesei and T. longibrachiatum, respectively.Key words: PCR fingerprinting, electrophoretic karyotypes, ITS, Trichoderma.

An oligonucleotide barcode for species identification in Trichoderma and Hypocrea

One of the biggest obstructions to studies on Trichoderma has been the incorrect and confused application of species names to isolates used in industry, biocontrol of plant pathogens and ecological surveys, thereby making the comparison of results questionable. Here we provide a convenient, on-line method for the quick molecular identification of Hypocrea/Trichoderma at the genus and species levels based on an oligonucleotide barcode: a diagnostic combination of several oligonucleotides (hallmarks) specifically allocated within the internal transcribed spacer 1 and 2 (ITS1 and 2) sequences of the rDNA repeat. The barcode was developed on the basis of 979 sequences of 88 vouchered species which displayed in total 135 ITS1 and 2 haplotypes. Oligonucleotide sequences which are constant in all known ITS1 and 2 of Hypocrea/Trichoderma but different in closely related fungal genera, were used to define genus-specific hallmarks. The library of species-, clade- and genus-specific hallmarks is stored in the MySQL database and integrated in the TrichOKey v. 1.0 - barcode sequence identification program with the web interface located on . TrichOKey v. 1.0 identifies 75 single species, 5 species pairs and 1 species triplet. Verification of the DNA-barcode was done by a blind test on 53 unknown isolates of Trichoderma, collected in Central and South America. The obtained results were in a total agreement with phylogenetic identification based on tef1 (large intron), NCBI BLAST of vouchered records and postum morphological analysis. We conclude that oligonucleotide barcode is a powerful tool for the routine identification of Hypocrea/Trichoderma species and should be useful as a complement to traditional methods.

In vitro water activity and pH dependence of mycelial growth and extracellular enzyme activities of Trichoderma strains with biocontrol potential

AIMS

Water activity (aw) and pH are probably the most important environmental parameters affecting the activities of mycoparasitic Trichoderma strains. Therefore it is important to collect information on the effects of these factors on mycelial growth and on the in vitro activities of extracellular enzymes involved in nutrient competition (e.g. beta-glucosidase, cellobiohydrolase and beta-xylosidase) and mycoparasitism (e.g. N-acetyl-beta-glucosaminidase, trypsin-like protease and chymotrypsin-like protease) of Trichoderma strains with biocontrol potential.

METHODS AND RESULTS

Water activity and pH dependence of the linear mycelial growth of five examined Trichoderma strains belonging to three different species groups was examined on yeast extract and soil extract media. Maximal growth rates were observed at aw 0.997 and pH 4.0 in the case of all strains. The activities of the examined extracellular enzymes at different aw and pH values were determined spectrophotometrically after incubation with chromogenic p-nitrophenyl and p-nitroaniline substrates. Maximal enzyme activities were measured at aw 0.950 for beta-glucosidase, trypsin-like protease and chymotrypsin-like protease, at 0.910 for cellobiohydrolase and at 0.993 for beta-xylosidase and N-acetyl-beta-glucosaminidase enzymes. Optimal pH values are suggested to be at 5.0 for beta-glucosidase, cellobiohydrolase and N-acetyl-beta-glucosaminidase, at 3.0 for beta-xylosidase, at 6.0 for trypsin-like protease and between 6.0 and 7.0 for chymotrypsin-like protease activities, respectively.

CONCLUSIONS

Extracellular enzymes of the examined mycoparasitic Trichoderma strains are able to display activities under a wider range of aw and pH values than those allowing mycelial growth.

SIGNIFICANCE AND IMPACT OF THE STUDY

Data about the effects of aw and pH on mycelial growth and extracellular enzyme activities of Trichoderma reveal useful information about the applicability of biocontrol strains in agricultural soils with specific water and pH relations.

Genetic engineering for improved xylose fermentation by yeasts

Xylose utilization is essential for the efficient conversion of lignocellulosic materials to fuels and chemicals. A few yeasts are known to ferment xylose directly to ethanol. However, the rates and yields need to be improved for commercialization. Xylose utilization is repressed by glucose which is usually present in lignocellulosic hydrolysates, so glucose regulation should be altered in order to maximize xylose conversion. Xylose utilization also requires low amounts of oxygen for optimal production. Respiration can reduce ethanol yields, so the role of oxygen must be better understood and respiration must be reduced in order to improve ethanol production. This paper reviews the central pathways for glucose and xylose metabolism, the principal respiratory pathways, the factors determining partitioning of pyruvate between respiration and fermentation, the known genetic mechanisms for glucose and oxygen regulation, and progress to date in improving xylose fermentations by yeasts.

The regulation of the vanadium chloroperoxidase from Curvularia inaequalis

The effects of carbon and nitrogen source on the regulation of the vanadium chloroperoxidase secreted by the fungus Curnularia inaequalis were investigated. The addition of glucose showed a repressing effect on both the observed messenger RNA level and the measured enzyme activities, whereas the addition of glutamate as nitrogen source and the addition of both glutamate and glycerol had no effect. Addition of vanadate had no effect on the level of mRNA. Eight hundred base pairs of the upstream promoter region of vCPO were sequenced and various features of interest are highlighted. Closer inspection of the mycelium revealed that once secreted, vCPO probably remains tightly associated with the hyphae in two forms, one of which may be a proform of the enzyme. A possible cleavage event at the C-terminus may lower its potential for hyphal association and permit its disassociation into the growth medium. A putative role for the vanadium chloroperoxidase is put forward.

Cel1, probably encoding a cellobiohydrolase lacking the substrate binding domain, is expressed in the initial infection phase of Claviceps purpurea on Secale cereale

At the host-pathogen interface of hyphae penetrating host cell walls in the rye ovary, a lack of cellulase-gold labeling of beta-1, 4-glucan in host cell walls indicates that enzymatic degradation of cellulose might be an important factor during the infection of rye by Claviceps purpurea. Using cbh1 from Trichoderma reesei as a probe, a putative cellulase gene (cel1) was isolated from a genomic library of the C. purpurea strain T5. The coding region of 1,616 bp contains two introns and a putative signal peptidase cleavage site, leaving a coding capacity of 437 amino acids for the mature protein. The derived amino acid sequence shares significant homology with other fungal cellobiohydrolases and lacks the substrate binding domain. Expression analysis using reverse transcriptase-polymerase chain reaction (RT-PCR) shows that cel1 is induced during the first days of infection of rye by C. purpurea. It may be involved in the penetration and degradation of host cell walls by depolymerizing plant beta-1, 4-glucan and, therefore, play a role in the infection process.

Analysis of Cre1 binding sites in the Trichoderma reesei cbh1 upstream region

A 1.5-kb XbaI-SacII fragment containing the upstream region of the Trichoderma reesei cellobiohydrolase I gene (cbh1) has been sequenced. The 1.5-kb fragment contains eight 6-bp sites having an identical or similar sequence to the consensus sequence for binding a catabolite repressor, Aspergillus nidulans CreA. Results of binding assays with the maltose-binding protein::Cre1(10-131) fusion protein (Cre1 is a catabolite repressor of T. reesei) and the cbh1 upstream region revealed that a 504-bp XbaI-NspV fragment (nucleotide position -1496 to -993) bearing three 6-bp sites, A1, A2, and A3, and a 356-bp NspV-MunI fragment (nucleotide position -994 to -639) bearing three 6-bp sites, B1, B2, and B3, were shifted in the electrophoretic mobility shift assay. DNase I footprinting experiments showed that the 6-bp sites A2, B1, B2, and B3 were protected from DNase I digestion.

Cloning, sequencing, and expression of the cellulase genes of Humicola grisea var. thermoidea

We have cloned an endoglucanase (EGI) gene and a cellobiohydrolase (CBHI) gene of Humicola grisea var. thermoidea using a portion of the Trichoderma reesei endoglucanase I gene as a probe, and determined their nucleotide sequences. The deduced amino acid sequence of EGI was 435 amino acids in length and the coding region was interrupted by an intron. The EGI lacks a hinge region and a cellulose-binding domain. The deduced amino acid sequence of CBHI was identical to the H. grisea CBHI previously reported, with the exception of three amino acids. The H. grisea EGI and CBHI show 39.8% and 37.7% identity with T. reesei EGI, respectively. In addition to TATA box and CAAT motifs, putative CREA binding sites were observed in the 5' upstream regions of both genes. The cloned cellulase genes were expressed in Aspergillus oryzae and the gene products were purified. The optimal temperatures of CBHI and EGI were 60 degrees C and 55-60 degrees C, respectively. The optimal pHs of these enzymes were 5.0. CBHI and EGI had distinct substrate specificities: CBHI showed high activity toward Avicel, whereas EGI showed high activity toward carboxymethyl cellulose (CMC).