Transcriptomic Analysis of Two Lentinula edodes Genotypes With Different Cadmium Accumulation Ability

Synergies between Carbon Sequestration, Nitrogen Utilization, and Mushroom Quality: A Comprehensive Review of Substrate, Fungi, and Soil Interactions

Mushroom cultivation offers a sustainable approach by combining carbon sequestration, nitrogen use, and quality food production. This review synthesizes current knowledge on the synergistic interactions between substrate composition, fungal species, environmental factors, and their cumulative effects on the carbon and nitrogen cycles, mushroom yield, and nutritional quality. Key research gaps include the long-term impact of spent mushroom substrate (SMS) on soil carbon dynamics, limited use of fungal diversity, and the vulnerability of substrates and enzyme activity to climate change. To address these challenges, this review proposes strategies such as blending fast- and slow-decomposing agricultural waste, enriching substrates with biochar, and using genetically modified fungi to enhance lignin breakdown and stress tolerance. It also highlights promising species like Ganoderma lucidum and Trametes versicolor, and emphasizes interspecies microbial synergy. A systems-based approach combining C:N optimization, microbial interaction, and substrate innovation is recommended to improve productivity, reduce waste, and support carbon-neutral cultivation.

Proteomics and physiologic analysis reveal different response strategies to cadmium stress in Lentinula edodes

Lentinula edodes (L. edodes) is the second most widely cultivated edible mushroom worldwide. However, it has the ability to accumulate cadmium (Cd), which poses significant health risks. Despite its significance, the protein-level response mechanisms to Cd stress remain insufficiently understood. This study aims to investigate the differential responses of the low-Cd-accumulating strain Le4606 and the high-Cd-accumulating strain Le4625 under Cd stress by biochemical and proteomic methodologies. The results indicate that Le4625 exhibits enhanced Cd absorption, proline accumulation, and vacuolar sequestration for detoxification, with ZRC1 detected exclusively at 7 h. Conversely, Le4606 demonstrates proficiency in glutathione-mediated detoxification, thioredoxin antioxidant activity, tricarboxylic acid cycle activity, autophagy, and Cd extrusion. Overall, vacuolar sequestration and glutathione-mediated detoxification are important for the differences in Cd accumulation. The distinct response strategies offer valuable insights into the underlying mechanisms of Cd accumulation. This research establishes a theoretical foundation for the breeding of low-Cd-accumulating cultivars, benefiting human health.

Lentinan alleviates cadmium-induced kidney injury by reducing cadmium accumulation via promoting cadmium excretion and metallothionein synthesis and regulating silencing information regulator1/nuclear factor erythroid 2-related factor 2/nuclear factor kappa-B signaling pathway

Cadmium (Cd) is a widely distributed environmental heavy metal pollutant. It is extremely toxic to the kidney. This study investigated the potential mechanisms of action of lentinan (LNT), a fungal polysaccharide, on protecting against Cd-induced kidney injury in mice. Male Kunming mice were administered with CdCl2 (2.5 mg/kg/b.w.) by intragastric gavage and LNT in drinking water (1 mg/mL) for 10 weeks. Histological examination revealed that LNT reduced the glomerular atrophy, lymphocyte infiltration, tubular congestion, and collagen accumulation caused by Cd exposure. However, oral administration of LNT decreased Cd levels in kidney by promoting the excretion of Cd in feces and increasing the production of metallothionein (MT) in the kidney. In addition, LNT treatment alleviated Cd-induced kidney excessive mitophagy by upregulating silencing information regulator1 (SIRT1) and prevented subsequent oxidative stress and inflammatory responses by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2) and downregulating nuclear factor kappa-B (NF-κB) signaling pathways. Further, the protein expression levels of profibrotic factors, including Tgf-β1, alpha smooth muscle actin, and collagen type I alpha 1 chain, and the progression of fibrosis, were significantly reduced in the kidneys of mice treated with LNT. Collectively, our findings suggest that LNT can relieve the nephrotoxicity of Cd by decreasing its accumulation via promoting Cd excretion and MT synthesis and regulating the SIRT1/Nrf2/NF-κB signaling pathway.

Gene expression analysis for stem browning in the mushroom Lentinula edodes

The mushroom Lentinula edodes, is consumed worldwide and has high industrial value because of its rich content of bioactive compounds such as ergothioneine and eritadenine. Currently, mainstream artificial cultivation methods for this mushroom typically use synthetic logs. However, browning of the stem's interior (stem browning) has been observed during the cultivation in some L. edodes strains. Although browning does not affect the taste or other qualities of the mushroom, it gives consumers a perception of "poor quality", and is a major challenge for producers. To identify the genes responsible for stem browning in this mushroom, we performed differential gene expression analysis during stem browning development and quantified it using real-time PCR. Our results indicated that certain oxidoreductases, such as tyrosinase and laccase, were significantly upregulated during the progression of stem browning. The results obtained in the present study provide valuable insights to address the problem of stem browning in mushroom L. edodes.

Combined Proteomic and Metabolomic Analyses Reveal the Comprehensive Regulation of Stropharia rugosoannulata Mycelia Exposed to Cadmium Stress

The potential of Stropharia rugosoannulata as a microbial remediation material for cadmium (Cd)-contaminated soil lies in its capacity to absorb and accumulate Cd in its mycelia. This study utilized the TMT and LC-MS techniques to conduct integrated proteomic and metabolomic analyses with the aim of investigating the mycelial response mechanisms of S. rugosoannulata under low- and high-Cd stresses. The results revealed that mycelia employed a proactive defense mechanism to maintain their physiological functions, leading to reduced sensitivity to low-Cd stress. The ability of mycelia to withstand high levels of Cd stress was influenced primarily by the comprehensive regulation of six metabolic pathways, which led to a harmonious balance between nitrogen and carbohydrate metabolism and to reductions in oxidative stress and growth inhibition caused by Cd. The results provide valuable insights into the molecular mechanisms involved in the response of S. rugosoannulata mycelia to Cd stress.

Safe Production Strategies for Soil-Covered Cultivation of Morel in Heavy Metal-Contaminated Soils

Morel is a popular edible mushroom with considerable medicinal and economic value which has garnered global popularity. However, the increasing heavy metal (HM) pollution in the soil presents a significant challenge to morels cultivation. Given the susceptibility of morels to HM accumulation, the quality and output of morels are at risk, posing a serious food safety concern that hinders the development of the morel industry. Nonetheless, research on the mechanism of HM enrichment and mitigation strategies in morel remains scarce. The morel, being cultivated in soil, shows a positive correlation between HM content in its fruiting body and the HM content in the soil. Therefore, soil remediation emerges as the most practical and effective approach to tackle HM pollution. Compared to physical and chemical remediation, bioremediation is a low-cost and eco-friendly approach that poses minimal threats to soil composition and structure. HMs easily enriched during morels cultivation were examined, including Cd, Cu, Hg, and Pb, and we assessed soil passivation technology, microbial remediation, strain screening and cultivation, and agronomic measures as potential approaches for HM pollution prevention. The current review underscores the importance of establishing a comprehensive system for preventing HM pollution in morels.

Transcriptome analysis reveals insight into the protective effect of N-acetylcysteine against cadmium toxicity in Ganoderma lucidum (Polyporales: Polyporaceae)

Ganoderma lucidum is widely cultivated and used as traditional medicine in China and other Asian countries. As a member of macrofungi, Ganoderma lucidum is also prone to bioaccumulation of cadmium and other heavy metals in a polluted environment, which affects the growth and production of Ganoderma lucidum, as well as human health. N-Acetyl-L-cysteine (NAC) is considered a general antioxidant and free radical scavenger that is involved in the regulation of various stress responses in plants and animals. However, whether NAC could regulate cadmium stress responses in macrofungi, particularly edible fungi, is still unknown. In this work, we found that the exogenous NAC could alleviate Cd-induced growth inhibition and reduce the cadmium accumulation in Ganoderma lucidum. The application of the NAC cloud also inhibit cadmium-induced H₂O₂ production in the mycelia. By using transcriptome analysis, 2920 and 1046 differentially expressed unigenes were identified in "Cd100 vs CK" and "NAC_Cd100 vs Cd100," respectively. These differential unigenes were classified into a set of functional categories and pathways, which indicated that various biological pathways may play critical roles in the protective effect of NAC against Cd‑induced toxicity in Ganoderma lucidum. Furthermore, it suggested that the ATP-binding cassette transporter, ZIP transporter, heat shock protein, glutathione transferases, and Cytochrome P450 genes contributed to the increased tolerance to cadmium stress after NAC application in Ganoderma lucidum. These results provide new insight into the physiological and molecular response of Ganoderma lucidum to cadmium stress and the protective role of NAC against cadmium toxicity.

Morphophysiological, proteomic and metabolomic analyses reveal cadmium tolerance mechanism in common wheat (Triticum aestivum L.)

Soil cadmium (Cd) contamination can reduce wheat yield and quality, thus threatening food security and human health. Herein, morphological physiology, Cd accumulation and distribution, proteomic and metabolomic analyses were performed (using wheat cultivars 'Luomai23' (LM, Cd-sensitive) and 'Zhongyu10' (ZY, Cd-tolerant) at the seedling stage with sand culture) to reveal Cd tolerance mechanism. Cd inhibited wheat growth, caused oxidative stress, hindered carbon and nitrogen metabolism, and altered the quantity and composition of root exudates. The root Cd concentration was lower in ZY than in LM by about 35% under 15 μM Cd treatments. ZY reduced Cd uptake through root exudation of amino acids and alkaloids. ZY also reduced Cd accumulation through specific up-regulation (twice) of major facilitator superfamily (MFS) proteins. Furthermore, ZY enhanced Cd cell wall fixation and vacuolar compartmentalization by increasing pectin contents, hemicellulose1 contents, and adenosine triphosphate binding cassette subfamily C member 1 (ABCC1) transporter expression, thus reducing the Cd organelle fraction of ZY by about 12% and 44% in root and shoot, respectively, compared with LM. Additionally, ZY had enhanced resilience to Cd due to increased antioxidant capacity, plasma membrane stability, nitrogen metabolism, and endoplasmic reticulum homeostasis, indicating that the increased Cd tolerance could be because of multi-level coordination. These findings provide a reference for exploring the molecular mechanism of Cd tolerance and accumulation, providing a basis for safe utilization of Cd-contaminated soil by breeding Cd-tolerant and low Cd-accumulating wheat varieties.

Transcriptome analysis of the response of Hypomyces chrysospermus to cadmium stress

Hypomyces chrysospermus is a fungal parasite that grows on Boletus species. One isolated strain of H. chrysospermus from B. griseus was obtained and proved of strong ability to tolerate and absorb cadmium (Cd) by previous research. However, the molecular mechanisms of underlying the resistance of H. chrysospermus to Cd stress have not been investigated. This study aimed to assess the effect of Cd stress on the global transcriptional regulation of H. chrysospermus. A total of 1,839 differentially expressed genes (DEGs) were identified under 120 mg/l Cd stress. Gene ontology (GO) enrichment analysis revealed that large amounts of DEGs were associated with cell membrane components, oxidoreductase activity, and transport activity. KEGG enrichment analysis revealed that these DEGs were mainly involved in the translation, amino acid metabolism, transport and catabolism, carbohydrate metabolism, and folding/sorting and degradation pathways under Cd stress. Moreover, the expression of DEGs encoding transporter proteins, antioxidant enzymes, nonenzymatic antioxidant proteins, detoxification enzymes, and transcription factors was associated with the Cd stress response. These results provide insights into the molecular mechanisms underlying Cd tolerance in H. chrysospermus and serve as a valuable reference for further studies on the detoxification mechanisms of heavy metal-tolerant fungi. Our findings may also facilitate the development of new and improved fungal bioremediation strategies.