Rapid response to environmental changes and abiotic stress to coordinate developmental programs is critical for plants. To accomplish this, plants use the ubiquitin proteasome pathway as a flexible and efficient mechanism to control protein stability and to direct cellular reactions. Here, we show that all three members of the R2R3 S23 MYB transcription factor subfamily, MYB1, MYB25, and MYB109, are degraded by the 26S proteasome, likely facilitated by a CUL3-based E3 ligase that uses MATH-BTB/POZ proteins as substrate adaptors. A detailed description of MYB1, MYB25, and MYB109 expression shows their nuclear localization and specific tissue specific expression patterns. It further demonstrates that elevated expression of MYB25 reduces sensitivities toward abscisic acid, osmotic and salt stress in Arabidopsis, while downregulation of all S23 members results in hypersensitivities. Transcriptional profiling in root and shoot of seedlings overexpressing MYB25 shows that the transcription factor widely affects cellular stress pathways related to biotic and abiotic stress control. Overall, the work extends our knowledge on proteins targeted by CUL3-based E3 ligases that use MATH-BTB/POZ proteins as substrate adaptors and provides first information on all members of the MYB S23 subfamily.

The turnip Brassica rapa has important economic value and represents a good model system to study gene function in crop plants. ERF/AP2 transcription factors are a major group of proteins that are often involved in regulating stress-responses and developmental programs. Some ERF/AP2 proteins are targets of CULLIN3-based E3 ligases that use BTB/POZ-MATH proteins as substrate receptors. These receptors bind the transcription factor and facilitate their ubiquitylation and subsequent degradation via the 26S proteasome. Here, we show tissue and stress-dependent expression patterns for three Brassica rapa ERF/AP2 proteins that are closely related to Arabidopsis thaliana AtRAP2.4. Cloning of the Brassica genes showed that the corresponding proteins can assemble with a BPM protein and CULLIN3, and that they are instable in a 26S proteasome dependent manner. This work demonstrates the conserved nature of the ERF/AP2-CULLIN3-based E3 ligase interplay, and represents a first step to analyze their function in a commercially relevant crop plant.

Background: Lion’s mane (Hericium erinaceus) mycelium produces erinacines, a suite of cyathane diterpenoids with established neuroactivities. While H. erinaceus fruit body tissue has its own characteristic secondary metabolites, it generally does not produce detectable amounts of erinacines. Substrate composition influences the erinacine content of H. erinaceus mycelial cultures, similar to production of secondary metabolites in other fungi. This study explored the relationship between biosynthetic gene expression and erinacine content in H. erinaceus, comparing fruit body tissue to mycelial tissue cultured in two liquid media formulations. Results: In this study, we compared erinacine production in H. erinaceus fruit body to mycelial tissue cultivated in two liquid media formulations (Complex and Minimal) by quantifying mRNA transcript levels of the erinacine biosynthetic genes eriE, eriG, eriI, eriC, eriJ, eriB, and eriM (collectively, eri genes) alongside high performance liquid chromatography (HPLC) evaluation of erinacines Q, P, A, and C. We also predicted coding sequences for these seven eri genes. The Complex media preparation yielded mycelium with significantly higher erinacine C content, while the Minimal media yielded mycelium with greater erinacine Q content, suggesting an alteration of the biosynthetic pathway related to differences in substrate composition. Despite evident differences in erinacine concentrations, mycelial eri gene transcript levels did not differ significantly between the two liquid media preparations. When evaluated by gene expression or compound concentration, erinacine biosynthesis was substantially greater in mycelia compared to fruit body tissue in H. erinaceus. Conclusions: Alongside the absence of detectable erinacines within fruit body samples, eri gene transcripts were consistently downregulated in the fruit body compared to the mycelium, particularly at early stages of the biosynthetic pathway. Substrate composition is a critical factor in production of erinacines by H. erinaceus, and large differences in mycelial erinacine content can occur without significant differences in expression of eri genes. Our data support the hypothesis that production of fungal secondary metabolites can be influenced by tissue type and substrate components, and that the expression of eri genes is enriched in the mycelium when compared to the fruit body.

Hericium erinaceus is a medicinal mushroom valued in the wellness industry for its neuroprotective, immunomodulatory, and antioxidant activities. While many extracts and bioactive compounds from both mycelium and fruit bodies have been characterized, the mechanisms driving their effects are not fully understood. Here, the transcriptomic and protein-level effects of H. erinaceus mycelium (HDLM) in human peripheral blood mononuclear cells (PBMCs) were investigated, along with antioxidant and iron chelating activity. A commercially available H. erinaceus fruit body extract (FBE) claiming high β-glucan content was included in a subset of assays to compare immune-related outcomes between mycelial and fruit body constituents. HDLM activated a wide array of immune- and oxidative stress-related transcripts and pathways, exhibited significant antioxidant activity, and consistently reduced IL-1β, TNF-α, and IL-8 during LPS challenge while maintaining low basal cytokine expression, indicating targeted immunomodulatory activity. FBE almost doubled production of IL-1β when challenged by LPS, whereas HDLM significantly decreased production of this stress mediator. HDLM also demonstrated augmented iron chelating ability when compared to FBE. Depending on tissue source and preparation methods, different H. erinaceus materials may either potentiate or quench stress responses, highlighting the need for further bioactivity and safety comparisons across H. erinaceus supplements, particularly with respect to cytokine regulation under conditions of immune challenge.

Background: Agarikon ( Fomitopsis officinalis, syn. Laricifomes officinalis ) is a fungus with millennia of traditional use across many cultures with modern research supporting the antimicrobial, antiviral, anticancer, antioxidant, and immune-modulating properties of both mycelium and fruit body. Due to the slow growth and old-growth forest habitat of agarikon fruit bodies, its mycelium represents an easily cultivated immunomodulating and stress buffering preparation, underscored by recent clinical trials of a blend of agarikon and Trametes versicolor mycelium. Methods: To provide a stronger mechanistic basis for the observed preclinical and clinical effects supported by agarikon mycelium, this preclinical study investigated the transcriptomic effects of agarikon mycelium in human peripheral blood mononuclear cells (PBMCs) under both basal and LPS-stimulated conditions ( padj < 0.05), alongside evaluations ( p < 0.05) of antioxidant, iron chelating, and kinase binding activity. Two agarikon fractions were also assessed ( p < 0.05) for effects on cell viability and proliferation and induction of select cytokine targets. Results: Under basal conditions, agarikon mycelium selectively engaged the innate immune response through IL-1 and NF-κB axes, balanced by increases in anti-inflammatory mediators such as IL-1RA and decreases in toll-like receptor transcripts. Under LPS-stimulated conditions, this innate immune response was modified, with measured increases in immune effectors (including TLR5 ) observed in response to induced stress, alongside accompanying transcript decreases in cytokine pathways that can overstimulate the immune system. Conclusion: Overall, agarikon mycelium demonstrated a coordinated, context-dependent immune response profile, supporting its stress-buffering and immune-modulating potential and warranting continued clinical validation.

Use of fungal mycelium as a vaccination adjunct may constitute a novel antiviral strategy to address newly emerging viruses. In a randomized, double-blind, placebo-controlled clinical trial, we evaluated safety and feasibility of fungal mycelium ( Fomitopsis officinalis and Trametes versicolor, FoTv) as an adjunct to human COVID-19 vaccination, as well as its impact on vaccine side-effects and anti-SARS-CoV-2 antibodies (Abs). We evaluated safety, feasibility, vaccine side-effects (across 5 days), and anti-SARS-CoV-2 Ab levels (across 6 months). Safety metrics were similar for the FoTv (N=52) and Placebo (N=38) groups and the approach was feasible. Participants with detectable Abs (from prior COVID antigen exposure) were classified as “COVID-Exposed” and those with undetectable Abs as “COVID-Naive.” FoTv, versus Placebo, significantly reduced side-effects in COVID-Naive, but not in COVID-Exposed individuals. In the COVID-Naive FoTv group, Ab responses were preserved across 6 months, an effect not observed among other groups. Adjunctive FoTv was safe, feasible, and reduced vaccine side-effects without compromising (and possibly increasing) Ab levels up to 6 months in participants without previous SARS-CoV-2 exposure. Use of fungal mycelia was successfully tested as an approach to prevent a novel pandemic virus (SARS-CoV-2), with potential application to H5N1/Bird Flu and other emerging viruses.