A native promoter and inclusion of an intron is necessary for efficient expression of GFP or mRFP in Armillaria mellea

Protocol for generating protoplasts of Trichoderma koningiopsis and transformation of plasmid DNA

Trichoderma koningiopsis is a filamentous fungus that produces numerous bioactive molecules and has the potential to be used as a biological control and plant growth-promoting agent. Here, we present a protocol for generating protoplasts of T. koningiopsis. We then describe four techniques for the stable transformation of plasmid DNA: polyethylene glycol (PEG)-mediated transformation of protoplasts, Agrobacterium-mediated transformation, electroporation of spores, and lipofection of mycelia. We then detail procedures for confirming the expression of a spCas9 gene using fluorescence microscopy.

Establishment of an efficient Agrobacterium tumefaciens-mediated transformation system for an Armillaria species, a host of the fully mycoheterotrophic plant Gastrodia elata

The genus Armillaria (Basidiomycota, Agaricales, Physalacriaceae) comprises pathogenic fungi that cause root-rot disease in plants, as well as species with low pathogenicity, some of which are hosts of the fully mycoheterotrophic orchid plant Gastrodia elata (Orchidaceae). To investigate the mechanisms underlying such special interactions between Armillaria fungi and G. elata, it is crucial to establish genetic transformation platforms for the Armillaria fungi and G. elata. In this study, an Armillaria strain Arm37 was isolated from G. elata, which can form symbiosis with G. elata in axenic culture under laboratory conditions. A vector pYT-EV containing a cassette for hygromycin-resistance selection and a cassette for expressing or silencing target genes was constructed. An Agrobacterium tumefaciens-mediated transformation (ATMT) system for Arm37 was successfully developed and optimized to achieve a transformation efficiency of 32%. The ATMT system was successfully used to express the reporter genes eGFP encoding enhanced green fluorescent protein and GUS encoding β-glucuronidase and to effectively silence the endogenous gene URA3 encoding orotidine-5'-phosphate decarboxylase in Arm37. This ATMT system established for Arm37 provides an efficient genetic tool for exploring the Arm37 genes that are involved in the unique interaction between the Armillaria fungi and fully mycoheterotrophic plant G. elata.

Development of a 2A peptide-based multigene expression system and its application for enhanced production of ganoderic acids in Ganoderma lucidum

Ganoderma has received much attention for its medicinal value, but the manipulation of multiple genes remains a challenge, hindering the genetic engineering of this species for the development of cell factories. Here, we first showed that the presence of an intron is necessary for the efficient expression of the endogenous cDNA of carboxin-resistant gene (cbx) in G. lucidum. Then, the self-cleaving function of 2 A peptide was investigated in G. lucidum by linking cbx cDNA to the codon-optimized hygromycin B-resistant gene (ophph) using the 2A-peptide sequence. The results showed that cbx cDNA and ophph can be successfully expressed in G. lucidum in a bicistronic manner from a single transcript. Moreover, the expression of both genes was not affected by the order within the 2 A cassette. In addition, simultaneous expression of cbx cDNA, ophph, and codon-optimized yellow fluorescent protein gene (opyfp) was conducted for the first time in G. lucidum using the 2 A peptide-based approach. The developed method was successfully applied to express both cDNA of the 3-hydroxy-3-methylglutaryl coenzyme A reductase (hmgr) and squalene epoxidase gene (se) for enhanced production of ganoderic acids (GAs) in G. lucidum. The engineered strain produced the maximum content of GA-Mk, GA-T, GA-S, and GA-Me were 26.56±3.53,39.58±3.75, 16.54±2.16, and 19.1±1.87 μg/100 mg dry weight, respectively. These values were 3.85-, 4.74-, 3.65-, and 3.23-fold higher than those produced by the control strain. The developed method will be useful for the manipulation of complex metabolic or regulatory pathways involving multiple genes in Ganoderma.

Synthetic enhancers including TFREs improve transgene expression in CHO cells

The human cytomegalovirus major immediate early gene (CMV) promoter is currently the most preferred promoter for recombinant therapeutic proteins (RTPs) production in CHO cells. To enhance the production of RTPs, five synthetic enhancers including multiple transcription factor regulatory elements (TFREs) were evaluated to enhance recombinant protein level in transient and stably transfected CHO cells. Compared with the control, four elements can enhance the report genes expression under both two transfected states. Further, the function of these four enhancers on human serum albumin (HSA) were investigated. We found that the transient expression can increase by up to 1.5 times, and the stably expression can maximum increase by up to 2.14 times. The enhancement of transgene expression was caused by the boost of their corresponding mRNA levels. Transcriptomics analysis was performed and found that transcriptional activation and cell cycle regulation genes were involved. In conclusion, optimization of enhancers in the CMV promoter could increase the production yield of transgene in transfected CHO cells, which has significance for developing high-yield CHO cell expression system.

Construction of nucleus-directed fluorescent reporter systems and its application to verification of heterokaryon formation in Morchella importuna

INTRODUCTION

Morchella importuna (M. importuna) is a rare fungus with high nutrition value and distinct flavor. Despite the successful artificial cultivation, its genetic characteristics and biological processes such as life cycle, reproductive system, and trophic mode remain poorly understood.

METHODS

Considering this, we constructed pEH2B and pMH2B vectors by fusing M. importuna endogenous histone protein H2B with fluorescent proteins eGFP or mCherry, respectively. Based on the constructed pEH2B and pMH2B vectors, nuclear fluorescence localization was performed via Agrobacterium tumefaciens-mediated transformation (ATMT). These two vectors were both driven by two endogenous promoters glyceraldehyde 3-phosphate dehydrogenase (GPD) and ubiquitin (UBI). The vector-based reporter systems were tested by the paired culture of two genetically modified strains pEH2B-labeled M04M24 (24e, MAT1-1-1) and pMH2B-abeled M04M26 (26m, MAT1-2-1).

RESULTS

The fluorescence observation and molecular identification results indicated the successful hyphal fusion and heterokaryon formation. We found that the expression of the reporter genes was stable, and it did not interfere with the growth of the fungus.

DISCUSSION

Our constructed nucleus-directed fluorescent systems in M. importuna can be used for monitoring the dynamic development and reproductive processes in living cells and also for monitoring the interaction between morels and plant roots. Therefore, morels exhibit the potential to be a candidate organism used for the research on basic biology and genetics of ascomycetes.

Stemphylium lycopersici Nep1-like Protein (NLP) Is a Key Virulence Factor in Tomato Gray Leaf Spot Disease

The fungus Stemphylium lycopersici (S. lycopersici) is an economically important plant pathogen that causes grey leaf spot disease in tomato. However, functional genomic studies in S. lycopersici are lacking, and the factors influencing its pathogenicity remain largely unknown. Here, we present the first example of genetic transformation and targeted gene replacement in S. lycopersici. We functionally analyzed the NLP gene, which encodes a necrosis- and ethylene-inducing peptide 1 (Nep1)-like protein (NLP). We found that targeted disruption of the NLP gene in S. lycopersici significantly compromised its virulence on tomato. Moreover, our data suggest that NLP affects S. lycopersici conidiospore production and weakly affects its adaptation to osmotic and oxidative stress. Interestingly, we found that NLP suppressed the production of reactive oxygen species (ROS) in tomato leaves during S. lycopersici infection. Further, expressing the fungal NLP in tomato resulted in constitutive transcription of immune-responsive genes and inhibited plant growth. Through gene manipulation, we demonstrated the function of NLP in S. lycopersici virulence and development. Our work provides a paradigm for functional genomics studies in a non-model fungal pathogen system.

Nucleus-directed fluorescent reporter system for promoter studies in the ectomycorrhizal fungus Laccaria bicolor

Currently ectomycorrhizal research suffers from a lack of molecular tools specifically adapted to study gene expression in fungal symbionts. Considering that, we designed pReNuK, a cloning vector for transcriptional promoter studies in the ectomycorrhizal basidiomycete Laccaria bicolor. The pReNuK vector offers the use of a nuclear localizing and chromatin incorporating histone H2B-mCherry fluorescent reporter protein and it is specifically optimized for efficient transgene expression in Laccaria. Moreover, pReNuK is designed to work in concert with Agrobacterium-mediated transformation under hygromycin B resistance selection. The functionality of the pReNuK reporter system was tested with the constitutive Laccaria glyceraldehyde 3-phosphate dehydrogenase gene promoter and further validated with the nitrogen source regulated nitrate reductase gene promoter. The expression of the nucleus-directed H2B-mCherry reporter is highly stable in time. Moreover, the transformation of Laccaria with pReNuK and the expression of the reporter do not have negative effects on the growth of the fungus. The pReNuK offers a novel tool for studying in vivo gene expression regulation in Laccaria, the leading fungal model for ectomycorrhizal research.

Efficient expression of heterologous genes by the introduction of the endogenous glyceraldehyde-3-phosphate dehydrogenase gene intron 1 in Ganoderma lucidum

Background

Ganoderma lucidum, a well-known medicinal mushroom, has received wide attention as a promising cell factory for producing bioactive compounds. However, efficient expression of heterologous genes remains a major challenge in Ganoderma, hindering metabolic regulation research and molecular breeding of this species.

Results

We show that the presence of glyceraldehyde-3-phosphate dehydrogenase gene (gpd) intron 1 at the 5′ end of, the 3′ end of, or within the heterologous phosphinothricin-resistant gene (bar) is efficient for its expression in G. lucidum. The enhanced expression of bar is exhibited by the higher accumulation of mRNA and increased amounts of protein. Moreover, the insertion of the gpd intron 1 in the β-glucuronidase gene (gus) elevates its mRNA accumulation and enzyme activity, which facilitates the use of this reporter gene in Ganoderma.

Conclusions

This study has demonstrated the importance of the introduction of gpd intron 1 for the efficient expression of bar and gus in G. lucidum. The presence of the gpd intron 1 in heterologous genes increases levels of mRNA accumulation and protein expression in basidiomycete Ganoderma. The developed method may be utilized in upregulating the expression of other heterologous genes in Ganoderma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01654-8.

Enhanced polyethylene glycol (PEG)-mediated protoplast transformation system for the phytopathogenic fungus, Ganoderma boninense

The basidiomycete fungus, Ganoderma boninense, has been identified as the main causal agent of oil palm basal stem rot (BSR) disease which has caused significant economic losses to the industry especially in Malaysia and Indonesia. Various efforts have been initiated to understand the disease and this plant pathogen especially at the molecular level. This is the first study of its kind on the development of a polyethylene glycol (PEG)-mediated protoplast transformation system for G. boninense. Based on the minimal inhibitory concentration study, 60 µg/mL and above of hygromycin were effective to completely inhibit G. boninense growth. Approximately 5.145 × 10⁷ cells/mL of protoplasts with the viability of 97.24% was successfully obtained from G. boninense mycelium tissue. The PEG-mediated G. boninense protoplast transformation using 1 µg of transformation vector, 25% of PEG solution, 10 min of pre-transformation incubation, and 30 min of post-transformation incubation has improved the transformation rate as compared with the previous reported protocols for other basidiomycete fungi. Optimization of four transformation parameters has improved the transformation efficiency of G. boninense from an average of 2 to 67 putative transformants. The presence of hygromycin phosphotransferase (hpt) and enhanced green fluorescent protein (eGFP) genes in the putative transformants was detected by PCR and verified by gene sequence analysis. Southern hybridization result further confirmed the integration of hpt gene in G. boninense transformants, and the green fluorescent signal was detected in the G. boninense transformants under the microscopic analysis. The establishment of this transformation system will accelerate the gene function studies of G. boninense especially those genes that may contribute to the pathogenesis of this fungus in oil palm.

Epidemiology, Biotic Interactions and Biological Control of Armillarioids in the Northern Hemisphere

Armillarioids, including the genera Armillaria, Desarmillaria and Guyanagaster, represent white-rot specific fungal saprotrophs with soilborne pathogenic potentials on woody hosts. They propagate in the soil by root-like rhizomorphs, connecting between susceptible root sections of their hosts, and often forming extended colonies in native forests. Pathogenic abilities of Armillaria and Desarmillaria genets can readily manifest in compromised hosts, or hosts with full vigour can be invaded by virulent mycelia when exposed to a larger number of newly formed genets. Armillaria root rot-related symptoms are indicators of ecological imbalances in native forests and plantations at the rhizosphere levels, often related to abiotic environmental threats, and most likely unfavourable changes in the microbiome compositions in the interactive zone of the roots. The less-studied biotic impacts that contribute to armillarioid host infection include fungi and insects, as well as forest conditions. On the other hand, negative biotic impactors, like bacterial communities, antagonistic fungi, nematodes and plant-derived substances may find applications in the environment-friendly, biological control of armillarioid root diseases, which can be used instead of, or in combination with the classical, but frequently problematic silvicultural and chemical control measures.

The CAG promoter maintains high-level transgene expression in HEK293 cells

The vast majority of therapeutic recombinant proteins are produced in mammalian cell lines. However, proteins generated in nonhuman cell lines, such as Chinese hamster ovary (CHO) cells, are decorated with human‐like glycan structures that differ from those of human cells, and these may induce immunogenic responses in human cells. Human embryonic kidney cells (HEK293F) are also extensively used as hosts for the expression of recombinant therapeutic proteins, but their utility is limited by the low expression of transgenes in these cells. Here, we investigated recombinant protein expression from eight frequently used promoters in transfected HEK293F cells. The expression levels and stability of the transgenes were evaluated by flow cytometry and qRT‐PCR. The most efficient expression (in terms of both mRNA and protein yields) was achieved using a cytomegalovirus (CMV) major immediate‐early enhancer combined with the chicken beta‐actin promoter (CAG) promoter, as compared to all other tested promoters under both transient and stable transfection conditions. In addition, application of mild hypothermia (i.e., 33 °C) after transfection improved the positive effect of the CMV enhancer fused to the chicken beta‐actin promoter (CAG promoter) on enhanced green fluorescent protein (eGFP) expression. Although the temperature sensitivity of the CMV promoter is greater than that of CAG promoter, recombinant protein levels were still highest when expression was driven by the CAG promoter. When eGFP was replaced with hepatitis B surface antigen, the CAG promoter still showed the highest transgene expression. In conclusion, our data show that the CAG promoter is a strong promoter for recombinant protein expression in HEK293F cells.

Recent developments of tools for genome and metabolome studies in basidiomycete fungi and their application to natural product research

Basidiomycota are a large and diverse phylum of fungi. They can make bioactive metabolites that are used or have inspired the synthesis of antibiotics and agrochemicals. Terpenoids are the most abundant class of natural products encountered in this taxon. Other natural product classes have been described, including polyketides, peptides, and indole alkaloids. The discovery and study of natural products made by basidiomycete fungi has so far been hampered by several factors, which include their slow growth and complex genome architecture. Recent developments of tools for genome and metabolome studies are allowing researchers to more easily tackle the secondary metabolome of basidiomycete fungi. Inexpensive long-read whole-genome sequencing enables the assembly of high-quality genomes, improving the scaffold upon which natural product gene clusters can be predicted. CRISPR/Cas9-based engineering of basidiomycete fungi has been described and will have an important role in linking natural products to their genetic determinants. Platforms for the heterologous expression of basidiomycete genes and gene clusters have been developed, enabling natural product biosynthesis studies. Molecular network analyses and publicly available natural product databases facilitate data dereplication and natural product characterisation. These technological advances combined are prompting a revived interest in natural product discovery from basidiomycete fungi.This article has an associated Future Leader to Watch interview with the first author of the paper.

Fluorescent protein expression in the ectomycorrhizal fungus Laccaria bicolor: a plasmid toolkit for easy use of fluorescent markers in basidiomycetes

For long time, studies on ectomycorrhiza (ECM) have been limited by inefficient expression of fluorescent proteins (FPs) in the fungal partner. To convert this situation, we have evaluated the basic requirements of FP expression in the model ECM homobasidiomycete Laccaria bicolor and established eGFP and mCherry as functional FP markers. Comparison of intron-containing and intronless FP-expression cassettes confirmed that intron-processing is indispensable for efficient FP expression in Laccaria. Nuclear FP localization was obtained via in-frame fusion of FPs between the intron-containing genomic gene sequences of Laccaria histone H2B, while cytosolic FP expression was produced by incorporating the intron-containing 5' fragment of the glyceraldehyde-3-phosphate dehydrogenase encoding gene. In addition, we have characterized the consensus Kozak sequence of strongly expressed genes in Laccaria and demonstrated its boosting effect on transgene mRNA accumulation. Based on these results, an Agrobacterium-mediated transformation compatible plasmid set was designed for easy use of FPs in Laccaria. The four cloning plasmids presented here allow fast and highly flexible construction of C-terminal in-frame fusions between the sequences of interest and the two FPs, expressed either from the endogenous gene promoter, allowing thus evaluation of the native regulation modes of the gene under study, or alternatively, from the constitutive Agaricus bisporus gpdII promoter for enhanced cellular protein localization assays. The molecular tools described here for cell-biological studies in Laccaria can also be exploited in studies of other biotrophic or saprotrophic basidiomycete species susceptible to genetic transformation.

Dual sgRNA-directed gene deletion in basidiomycete Ganoderma lucidum using the CRISPR/Cas9 system

Ganoderma lucidum is an important medicinal mushroom in traditional Chinese medicine. However, the lack of adequate genetic tools has hindered molecular genetic research in and the genetic modification of this species. Here, we report that the presence of an intron is necessary for the efficient expression of the heterologous phosphinothricin-resistance and green fluorescent protein genes in G. lucidum. Moreover, we improved the CRISPR/Cas9-mediated gene disruption frequency in G. lucidum by adding an intron upstream of the Cas9 gene. Our results showed that the disruption frequency of the orotidine 5'-monophosphate decarboxylase gene (ura3) in transformants containing the glyceraldehyde-3-phosphate dehydrogenase gene intron in the Cas9 plasmid is 14-18 in 10⁷ protoplasts, which is 10.6 times higher than that in transformants without any intron sequence. Furthermore, genomic fragment deletions in the ura3 and GL17624 genes were achieved via a dual sgRNA-directed CRISPR/Cas9 system in G. lucidum. We achieved a ura3 deletion frequency of 36.7% in G. lucidum. The developed method provides a powerful platform to generate gene deletion mutants and will facilitate functional genomic studies in G. lucidum.

Bovistol B, bovistol D and strossmayerin: Sesquiterpene metabolites from the culture filtrate of the basidiomycete Coprinopsis strossmayeri

Basidiomycete fungi are a rich source of natural products with a diverse array of potentially exploitable bioactivities. Two dimeric sesquiterpenes, bovistol B (1) and D (2), and one monomeric sesquiterpene, strossmayerin (7), were isolated from the culture filtrate of the basidiomycete fungus Coprinopsis strossmayeri. The structures were determined through a combination of MS and 1D/2D NMR spectroscopic techniques. Likely monomeric precursors, identified on the basis of HRMS analysis, allow a plausible biosynthetic pathway to be proposed for the biosynthesis of 1 and 2, involving the dimerisation of the monomer through a hetero-Diels-Alder mechanism. A gene cluster, including a putative sesquiterpene 1-11 cyclase, was identified through phylogenetic and RNA-seq analysis, and is proposed to be responsible for the biosynthesis of 1 and 2.

Fhl1p protein, a positive transcription factor in Pichia pastoris, enhances the expression of recombinant proteins

Background

The methylotrophic yeast Pichia pastoris is well-known for the production of a broad spectrum of functional types of heterologous proteins including enzymes, antigens, engineered antibody fragments, and next gen protein scaffolds and many transcription factors are utilized to address the burden caused by the high expression of heterologous proteins. In this article, a novel P. pastoris transcription factor currently annotated as Fhl1p, an activator of ribosome biosynthesis processing, was investigated for promoting the expression of the recombinant proteins.

Results

The function of Fhl1p of P. pastoris for improving the expression of recombinant proteins was verified in strains expressing phytase, pectinase and mRFP, showing that the productivity was increased by 20–35%. RNA-Seq was used to study the Fhl1p regulation mechanism in detail, confirming Fhl1p involved in the regulation of rRNA processing genes, ribosomal small/large subunit biogenesis genes, Golgi vesicle transport genes, etc., which contributed to boosting the expression of foreign proteins. The overexpressed Fhl1p strain exhibited increases in the polysome and monosome levels, showing improved translation activities.

Conclusion

This study illustrated that the transcription factor Fhl1p could effectively enhance recombinant protein expression in P. pastoris. Furthermore, we provided the evidence that overexpressed Fhl1p was related to more active translation state.

Armillaria

Lingering in forests around the world, some of the largest and oldest terrestrial organisms on earth hide in plain sight. In this Quick Guide, Sipos et al. shed light on the biology of the Armillaria fungi.

Exploring molecular tools for transformation and gene expression in the cultivated edible mushroom Agrocybe aegerita

Agrocybe aegerita is a cultivated edible mushroom in numerous countries, which also serves as a model basidiomycete to study fruiting body formation. Aiming to create an easily expandable customised molecular toolset for transformation and constitutive gene of interest expression, we first created a homologous dominant marker for transformant selection. Progeny monokaryons of the genome-sequenced dikaryon A. aegerita AAE-3 used here were identified as sensitive to the systemic fungicide carboxin. We cloned the wild-type gene encoding the iron-sulphur protein subunit of succinate dehydrogenase AaeSdi1 including its up- and downstream regions, and introduced a single-point mutation (His237 to Leu) to make it confer carboxin resistance. PEG-mediated transformation of protoplasts derived from either oidia or vegetative monokaryotic mycelium with the resulting carboxin resistance marker (Cbx^R) plasmid pSDI1E3 yielded carboxin-resistant transformants in both cases. Plasmid DNA linearised within the selection marker resulted in transformants with ectopic multiple insertions of plasmid DNA in a head-to-tail repeat-like fashion. When circular plasmid was used, ectopic single integration into the fungal genome was favoured, but also gene conversion at the homologous locus was seen in 1 out of 11 analysed transformants. Employing Cbx^R as selection marker, two versions of a reporter gene construct were assembled via Golden Gate cloning which allows easy recombination of its modules. These consisted of an eGFP expression cassette controlled by the native promoter P_AaeGPDII and the heterologous terminator T_nos, once with and once without an intron in front of the eGFP start codon. After protoplast transformation with either construct as circular plasmid DNA, GFP fluorescence was detected with either transformants, indicating that expression of eGFP is intron-independent in A. aegerita. This paves the way for functional genetics approaches to A. aegerita, e.g., via constitutive expression of fruiting-related genes.

Use of green fluorescent protein to monitor fungal growth in biomass hydrolysate

A reporter gene encoding green fluorescent protein (GFP) was introduced into the ascomycete Coniochaeta ligniaria NRRL30616, and fluorescence of cultures was monitored as a measure of cell growth. Fluorescence in the GFP-expressing strain was measured during growth of cells in defined and complex media as well as in the liquor derived from pretreatment of corn stover, an agricultural residue. Fluorescence mirrored growth of cultures, as measured by optical density and counts of colony forming units. Because traditional methods to monitor growth cannot be used in biomass liquors due to its fibrous, dark-colored nature, the speed and convenience of using GFP to monitor growth is advantageous. Fluorescence of cultures in biomass hydrolysate also correlated with the concentration of furfural in hydrolysate. Furfural and other compounds, present in hydrolysate due to physico-chemical pretreatment of biomass, are inhibitory to fermenting microbes. Therefore, measurement of fluorescence in GFP-expressing C. ligniaria is a proxy for measures of microbial growth and furfural consumption, and serves as a convenient indicator of metabolism of fermentation inhibitors in biomass hydrolysate.

Frequent diploidisation of haploid Armillaria ostoyae strains in an outdoor inoculation experiment

Very little is known about the biology and ecology of haploid Armillaria strains in nature. In this outdoor inoculation experiment, we assessed the virulence of six haploid Armillariaostoyae strains along with their diploid parent towards 2-year-old seedlings and 4-year-old saplings of Norway spruce (Picea abies), and determined their ability to colonise freshly cut stumps. As inoculum source an Armillaria-colonised hazelnut (Corylus avellana) stem segment was inserted into the soil substrate. Re-isolations from mycelial fans at the root collar of infected trees or stumps were made. Surprisingly, not a single haploid re-isolate could be recovered. Microsatellite genotyping of 133 re-isolates suggests that the inoculated haploid strains were diploidised either by mating propagules (basidiospores or haploid mycelia) already present in the soil substrate or naturally disseminated in the course of the experiment from nearby forests. Consequently, no conclusion about the infectious ability of haploid Armillaria mycelia under natural conditions can be drawn. Nonetheless, the diploid half-sib families resulting from the diploidisation showed varying degrees of virulence, with a high correlation between the experiment with 2-year-old seedlings and 4-year-old saplings. Despite extensive genotyping of re-isolates, no evidence for somatic recombination between haploid mating propagules and diploidised mycelia was detected, suggesting that this is an uncommon phenomenon in A. ostoyae.

A silver bullet in a golden age of functional genomics: the impact of Agrobacterium-mediated transformation of fungi

The implementation of Agrobacterium tumefaciens as a transformation tool revolutionized approaches to discover and understand gene functions in a large number of fungal species. A. tumefaciens mediated transformation (AtMT) is one of the most transformative technologies for research on fungi developed in the last 20 years, a development arguably only surpassed by the impact of genomics. AtMT has been widely applied in forward genetics, whereby generation of strain libraries using random T-DNA insertional mutagenesis, combined with phenotypic screening, has enabled the genetic basis of many processes to be elucidated. Alternatively, AtMT has been fundamental for reverse genetics, where mutant isolates are generated with targeted gene deletions or disruptions, enabling gene functional roles to be determined. When combined with concomitant advances in genomics, both forward and reverse approaches using AtMT have enabled complex fungal phenotypes to be dissected at the molecular and genetic level. Additionally, in several cases AtMT has paved the way for the development of new species to act as models for specific areas of fungal biology, particularly in plant pathogenic ascomycetes and in a number of basidiomycete species. Despite its impact, the implementation of AtMT has been uneven in the fungi. This review provides insight into the dynamics of expansion of new research tools into a large research community and across multiple organisms. As such, AtMT in the fungi, beyond the demonstrated and continuing power for gene discovery and as a facile transformation tool, provides a model to understand how other technologies that are just being pioneered, e.g. CRISPR/Cas, may play roles in fungi and other eukaryotic species.

Impact of different promoters, promoter mutation, and an enhancer on recombinant protein expression in CHO cells

In the present study, six commonly used promoters, including cytomegalovirus major immediate-early (CMV), the CMV enhancer fused to the chicken beta-actin promoter (CAG), human elongation factor-1α (HEF-1α), mouse cytomegalovirus (mouse CMV), Chinese hamster elongation factor-1α (CHEF-1α), and phosphoglycerate kinase (PGK), a CMV promoter mutant and a CAG enhancer, were evaluated to determine their effects on transgene expression and stability in transfected CHO cells. The promoters and enhancer were cloned or synthesized, and mutation at C-404 in the CMV promoter was generated; then all elements were transfected into CHO cells. Stably transfected CHO cells were identified via screening under the selection pressure of G418. Flow cytometry, qPCR, and qRT-PCR were used to explore eGFP expression levels, gene copy number, and mRNA expression levels, respectively. Furthermore, the erythropoietin (EPO) gene was used to test the selected strong promoter. Of the six promoters, the CHEF-1α promoter yielded the highest transgene expression levels, whereas the CMV promoter maintained transgene expression more stably during long-term culture of cells. We conclude that CHEF-1α promoter conferred higher level of EPO expression in CHO cells, but the CMV promoter with its high levels of stability performs best in this vector system.

The good, the bad and the tasty: The many roles of mushrooms

Fungi are often inconspicuous in nature and this means it is all too easy to overlook their importance. Often referred to as the "Forgotten Kingdom", fungi are key components of life on this planet. The phylum Basidiomycota, considered to contain the most complex and evolutionarily advanced members of this Kingdom, includes some of the most iconic fungal species such as the gilled mushrooms, puffballs and bracket fungi. Basidiomycetes inhabit a wide range of ecological niches, carrying out vital ecosystem roles, particularly in carbon cycling and as symbiotic partners with a range of other organisms. Specifically in the context of human use, the basidiomycetes are a highly valuable food source and are increasingly medicinally important. In this review, seven main categories, or 'roles', for basidiomycetes have been suggested by the authors: as model species, edible species, toxic species, medicinal basidiomycetes, symbionts, decomposers and pathogens, and two species have been chosen as representatives of each category. Although this is in no way an exhaustive discussion of the importance of basidiomycetes, this review aims to give a broad overview of the importance of these organisms, exploring the various ways they can be exploited to the benefit of human society.