The molecular genetics of cultivated mushrooms

Advancements in genetic studies of mushrooms: a comprehensive review

Genetic studies in mushrooms, driven by innovations such as CRISPR-Cas9 genome editing and RNA interference, transform our understanding of these enigmatic fungi and their multifaceted roles in agriculture, medicine, and conservation. This comprehensive review explores the rationale and significance of genetic research in mushrooms, delving into the ethical, regulatory, and ecological dimensions of this field. CRISPR-Cas9 emerges as a game-changing technology, enabling precise genome editing, targeted gene knockouts, and pathway manipulation. RNA interference complements these efforts by downregulating genes for improved crop yield and enhanced pest and disease resistance. Genetic studies also contribute to the conservation of rare species and developing more robust mushroom strains, fostering sustainable cultivation practices. Moreover, they unlock the potential for discovering novel medicinal compounds, offering new horizons in pharmaceuticals and nutraceuticals. As emerging technologies and ethical considerations shape the future of mushroom research, these studies promise to revolutionize our relationship with these fungi, paving the way for a more sustainable and innovative world.

Blue light exposure and nutrient conditions influence the expression of genes involved in simultaneous hyphal knot formation in Coprinopsis cinerea

Light and nutrients are crucial environmental factors influencing fungal sexual reproduction. Blue light induces simultaneous hyphal knot formation in Coprinopsis cinerea mycelia grown on low-glucose media but not in mycelia grown on high-glucose media. Many hyphal knots are visible in the arc near the edge of the colony one day after 15 min of blue light stimulation. These findings collectively suggest that blue light accelerates hyphal knot induction in nutrient-limited conditions. Transcriptome analysis revealed that gene expression after light exposure is divided into at least two major stages. In the first stage, genes coding for fasciclin (fas1), cyclopropane-fatty-acyl-phospholipid synthases (cfs1 and cfs2), and putative lipid exporter (nod1) are highly expressed after 1 h of light exposure in the mycelial region where the hyphal knot will be developed. These genes are upregulated by blue light and not influenced by glucose condition and mating. These results suggest that although some of the genes are critical for induction of the hyphal knots, they are not sufficient for hyphal knot development. In the second gene expression stage, genes encoding galectins (cgl1-3), farnesyl cysteine-carboxyl methyltransferases, mating pheromone-containing protein, nucleus protein (ich1), and laccase (lcc1) are specifically upregulated at 10-16 h after blue light exposure when the mycelia are cultivated on low-glucose media. These genes might be involved in the architecture of hyphal knots or signal transduction for further fruiting body development. These results contribute to the understanding of the effect of environmental factors on sexual reproduction in basidiomycetous fungi.

A rapid PCR-RFLP method for monitoring genetic variation among commercial mushroom species*

We report the development of a simplified procedure for restriction fragment length polymorphism (RFLP) analysis of mushrooms. We have adapted standard molecular techniques to be amenable to an undergraduate laboratory setting in order to allow students to explore basic questions about fungal diversity and relatedness among mushroom species. The streamlined protocols allowed students to practice important molecular techniques within the context of self-designed investigative projects. This laboratory experience provided opportunities for students to practice strategies for examining molecular diversity among species.

Cell wall-associated enzymes in fungi

This review compiles and discusses previous reports on the identity of wall-associated enzymes (WAEs) in fungi and addresses critically the widely different terminologies used in the literature to specify the type of bonding of WAEs to other entities of the cell wall compartment, the extracellular matrix (ECM). A facile and rapid fractionation protocol for catalytically active WAEs is presented, which uses crude cell walls as the experimental material, a variety of test enzymes (including representatives of polysaccharide synthases and hydrolases, phosphatases, gamma-glutamyltransferases, pyridine-nucleotide dehydrogenases and phenol-oxidising enzymes) and a combination of simple hydrophilic and hydrophobic extractants. The protocol provides four fully operationally defined classes of WAEs, with constituent members of each class displaying the same basic type of physicochemical interaction with binding partners in situ. The routine application of the protocol to different species and cell types could yield easily accessible data useful for building-up a general objective information retrieval system of WAEs, suitable as an heuristic basis both for the unravelling of the role and for the biotechnological potentialities of WAEs. A detailed account is given of the function played in the ECM by WAEs in the metabolism of chitin (chitin synthase, chitinase and beta-N-acetylhexosaminidase) and of phenols (tyrosinase).

Efficient isolation of genes differentially expressed on cellulose by suppression subtractive hybridization in Agaricus bisporus

The production of cellulases on minimal medium in the edible mushroom Agaricus bisporus is regulated by the carbon source: induced by cellulose and repressed by glucose. In order to isolate cellulose-growth specific sequences, a cDNA library from A. bisporus using suppression subtractive hybridization (SSH) was constructed. Northern blot analysis indicated that a high level of enrichment was achieved; 183 clones were isolated. A preliminary screen with cellulose-specific genes of A. bisporus (cel1, cel2, cel3 and cel4) using Southern hybridization resulted in 28 clones to be cel3, and 5 clones were cel2. The remaining 144 clones were sequenced. Partial sequences of the following genes were found: a beta-glucosidase homologue of the blvk gene of Kluyveromyces marxianus; a cellulase homologue of an endoglucanase (avicellase III) of Aspergillus aculeatus, four different xylanases homologue of the xyn genes of different fungi, and one hexose transporter homologue to the hxtA gene of Aspergillus parasiticus. The apparent full-length of two hydrophobins homologue to the abh3 gene of A. bisporus and one histone homologue to the h2a gene of Aspergillus niger were also found. The remaining sequences did not have homology to any known genes.

Filamentous fungi as cell factories for heterologous protein production

Filamentous fungi have been used as sources of metabolites and enzymes for centuries. For about two decades, molecular genetic tools have enabled us to use these organisms to express extra copies of both endogenous and exogenous genes. This review of current practice reveals that molecular tools have enabled several new developments. But it has been process development that has driven the final breakthrough to achieving commercially relevant quantities of protein. Recent research into gene expression in filamentous fungi has explored their wealth of genetic diversity with a view to exploiting them as expression hosts and as a source of new genes. Inevitably, the progress in the 'genomics' technology will further develop high-throughput technologies for these organisms.