Differential gene expression profiling analysis in Pleurotus ostreatus during interspecific antagonistic interactions with Dichomitus squalens and Trametes versicolor

Geniposide suppresses thermogenesis via regulating PKA catalytic subunit in adipocytes

Geniposide has been widely found to ameliorate many metabolic diseases. The recruitment and activation of brown/beige adipocytes are effective and promising methods for counteracting obesity and related diseases. However, the effect of geniposide on thermogenesis of adipocytes and its underlying mechanism have not yet been investigated. Here, we demonstrate that geniposide (25 mg/kg) reduces body temperature and cold tolerance of mice via suppressing thermogenic genes in interscapular brown adipose tissue (iBAT) and inguinal white adipose tissue (iWAT). Consistently, geniposide (20 mg/mL) suppresses thermogenic capacity of adipocytes (brown adipocytes and 3T3L1 preadipocyte cells) in vitro. Mechanistically, geniposide reduces the level of protein kinase A (PKA) catalytic subunit and further suppresses transcription activity and protein stability of uncoupling protein 1 (UCP1), leading to reduction of thermogenic capacity in adipocytes. Moreover, pharmacological PKA activation reverses geniposide-induced UCP1 inhibition, which indicated that geniposide suppresses thermogenesis of adipocytes via regulating PKA signaling. Together, our findings suggest that geniposide is an inhibitor of fat thermogenesis, establishing a novel function characteristic of geniposide.

Coprinopsis cinerea uses laccase Lcc9 as a defense strategy to eliminate oxidative stress during fungal-fungal interactions

Frequently, laccases are triggered during fungal cocultivation for overexpression. The function of these activated laccases during coculture has not been clarified. Previously, we reported that Gongronella sp. w5 (w5) (Mucoromycota, Mucoromycetes) specifically triggered the laccase Lcc9 overexpression in Coprinopsis cinerea (Basidiomycota, Agaricomycetes). To systematically analyze the function of the overexpressed laccase during fungal interaction, C. cinerea mycelia before and after the initial Lcc9 overexpression were chosen for transcriptome analysis. Results showed that accompanied by specific utilization of fructose as carbohydrate substrate, oxidative stress derived from antagonistic compounds secreted by w5 appears to be a signal critical for laccase production in C. cinerea. Reactive oxygen species (ROS) decrease in the C. cinerea wild-type strain followed the increase in laccase production and then, lcc9 transcription and laccase activity stopped. By comparison, increased H₂O₂ content and mycelial ROS levels were observed during the entire cocultivation in lcc9 silenced C. cinerea strains. Moreover, lcc9 silencing slowed down the C. cinerea mycelial growth, affected hyphal morphology, and decreased the asexual sporulation in coculture. Our results showed that intracellular ROS acted as signal molecules to stimulate defense responses by C. cinerea with the expression of oxidative stress response regulator Skn7 and various detoxification proteins. Lcc9 takes part as a defense strategy to eliminate oxidative stress during the interspecific interaction with w5. Importance: The overproduction of laccase during interspecific fungal interactions is notoriously known. However, the exact role of the up-regulated laccases remains underexplored. Based on comparative transcriptomic analysis of C. cinerea and gene silencing of laccase Lcc9, here we show that oxidative stress derived from antagonistic compounds secreted by Gongronella sp. w5 was a signal critical for laccase Lcc9 production in Coprinopsis cinerea. Intracellular ROS acted as signal molecules to stimulate defense responses by C. cinerea with the expression of oxidative stress response regulator Skn7 and various detoxification proteins. Ultimately, Lcc9 takes part as a defense strategy to eliminate oxidative stress and help cell growth and development during the interspecific interaction with Gongronella sp. w5. These findings deepened our understanding of fungal interactions in their natural population and communities.

Enhancement of laccase production by Cerrena unicolor through fungal interspecies interaction and optimum conditions determination

The present study aimed to identify a pair of fungal strains that promote laccase production in the co-cultivation of white-rot basidiomycetes and to determine the optimum conditions to enhance enzyme synthesis under co-fermentation of mandarin peels. Co-cultivation of Cerrena unicolor with Trametes versicolor, Lenzites betulina, and Panus lecomtei led to up-regulation of laccase activity. Moreover, interspecific interaction of Cerrena unicolor and Trametes versicolor induced the production of two new laccase isoenzymes. By contrast, interactions of Cerrena unicolor with Trametes coccineus and Trametes hirsuta resulted in a multiple decreased ability of Cerrena unicolor to produce laccase. Co-cultivation of Cerrena unicolor with other fungi 3- to 12-fold down-regulated manganese peroxidase (MnP) activity. The outcomes of these fungal interactions are closely related to the initial concentration and availability of the nutrients, the partners' inoculum ratio, time, and sequence of their inoculation. Co-cultivation of Cerrena unicolor and Trametes versicolor in fermenter resulted in the accumulation of 476 U/mL laccase and 1.12 U/mL MnP.

Morpho-physiological and transcriptome analysis provide insights into the effects of zinc application on nitrogen accumulation and metabolism in wheat (Triticum aestivum L.)

Nitrogen (N) is the essential nutrient for wheat growth and development, its accumulation and metabolism controlled by many other elements. Zinc (Zn) is one of the important elements which tends to have effects on plant N homeostasis. Here in our study, 0 μM and 5 μM Zn was applied to the wheat seedlings culturing in 5 mM (+N) and 0.5 mM (-N) N treatments, respectively. The results showed that the shoot and root length growth performance, total N, NO₃^-, and amino acid concentrations, glutamine synthetase (GS) activity of wheat were facilitated by 5 μM Zn application under + N and -N conditions. Quantitative real-time PCR (qRT-PCR) analysis indicated that several NO₃^- transporters genes (TaNRT2.1, TaNPF7.1 and TaNPF7.2) and the genes encoding GS (TaGS1 and TaGS2) were induced by 5 μM Zn. In addition, transcriptional changes in wheat shoots and roots with Zn application were tested by RNA-seq techniques. A total of 147/551 induced and 36/2162 reduced differentially expression genes (DEGs) was detected in wheat shoots/roots, respectively. GO and KEGG enrichment analyses showed that 5 μM Zn mainly affected the glutathione (GSH) metabolism, phenylpropanoid biosynthesis and amino acid metabolism, involving in N homeostasis. Furthermore, the relative expression of genes related to phenylalanine, cysteine and methionine metabolism was induced by 5 μM Zn to promote the amino acid accumulation. Overall, these results highlight the facilitating of N accumulation by low level Zn, and provide an insight into the effects of Zn on N metabolism in wheat.

Seeking the Roles for Fungal Small-Secreted Proteins in Affecting Saprophytic Lifestyles

Small secreted proteins (SSPs) comprise 40–60% of the total fungal secretome and are present in fungi of all phylogenetic groups, representing the entire spectrum of lifestyles. They are characteristically shorter than 300 amino acids in length and have a signal peptide. The majority of SSPs are coded by orphan genes, which lack known domains or similarities to known protein sequences. Effectors are a group of SSPs that have been investigated extensively in fungi that interact with living hosts, either pathogens or mutualistic systems. They are involved in suppressing the host defense response and altering its physiology. Here, we aim to delineate some of the potential roles of SSPs in saprotrophic fungi, that have been bioinformatically predicted as effectors, and termed in this mini-review as “effector-like” proteins. The effector-like Ssp1 from the white-rot fungus Pleurotus ostreatus is presented as a case study, and its potential role in regulating the ligninolytic system, secondary metabolism, development, and fruiting body initiation are discussed. We propose that deciphering the nature of effector-like SSPs will contribute to our understanding of development and communication in saprophytic fungi, as well as help, to elucidate the origin, regulation, and mechanisms of fungal-host, fungal-fungal, and fungal-bacterial interactions.

Comparative transcriptomics and transcriptional regulation analysis of enhanced laccase production induced by co-culture of Pleurotus eryngii var. ferulae with Rhodotorula mucilaginosa

The co-culturing of Pleurotus eryngii var. ferulae and Rhodotorula mucilaginosa was confirmed in our previous studies to be an efficient strategy to improve laccase production by submerged fermentation. To determine the possible regulation principles underlying this behaviour, comparative transcriptomic analysis was performed on P. eryngii var. ferulae to investigate the differential expression of genes in co-culture. RNA-seq analysis showed that genes concerning xenobiotic biodegradation and expenditure of energy were upregulated. However, genes related to oxidative stress were downregulated. In addition, the transcription levels of laccase isoenzymes were not consistent in the co-culture system: 3 laccase genes (lacc1, lacc2, lacc12) were upregulated, and 3 laccase genes (lacc4, lacc6, lacc9) were downregulated. The enhancement in laccase activity can be due to upregulation of a laccase heterodimer encoded by the genes lacc2 and ssPOXA3a (or ssPOXA3b), whose expression levels were increased by 459% and 769% (or 585% for ssPOXA3b) compared with those of a control, respectively. β-Carotene produced by R. mucilaginosa upregulated the transcription of lacc2 only. Combining these results with an analysis of cis-acting responsive elements indicated that four transcription factors (TFs) had potential regulatory effects on the transcription of laccase genes. It was supposed that TFa regulated lacc transcription by binding with methyl jasmonate and heat shock response elements. The expression of TFb, TFc, and TFd was regulated by β-carotene. However, β-carotene had no effect on TFa expression. These results provide a possible mechanism for the regulation of laccase gene transcription in the co-culture system and are also beneficial for the future intensification of fungal laccase production.

Manipulating the Expression of Small Secreted Protein 1 (Ssp1) Alters Patterns of Development and Metabolism in the White-Rot Fungus Pleurotus ostreatus

The function of small secreted proteins (SSPs) in saprotrophic fungi is, for the most part, unknown. The white-rot mushroom Pleurotus ostreatus produces considerable amounts of SSPs at the onset of secondary metabolism, during colony development, and in response to chemical compounds such as 5-hydroxymethylfurfural and aryl alcohols. Genetic manipulation of Ssp1, by knockdown (KDssp1) or overexpression (OEssp1), indicated that they are, in fact, involved in the regulation of the ligninolytic system. To elucidate their potential involvement in fungal development, quantitative secretome analysis was performed during the trophophase and the idiophase and at a transition point between the two growth phases. The mutations conferred a time shift in the secretion and expression patterns: OEssp1 preceded the entrance to idiophase and secondary metabolism, while KDssp1 was delayed. This was also correlated with expression patterns of selected genes. The KDssp1 colony aged at a slower pace, accompanied by a slower decline in biomass over time. In contrast, the OEssp1 strain exhibited severe lysis and aging of the colony at the same time point. These phenomena were accompanied by variations in yellow pigment production, characteristic of entrance of the wild type into idiophase. The pigment was produced earlier and in a larger amount in the OEssp1 strain and was absent from the KDssp1 strain. Furthermore, the dikaryon harboring OEssp1 exhibited a delay in the initiation of fruiting body formation as well as earlier aging. We propose that Ssp1 might function as a part of the fungal communication network and regulate the pattern of fungal development and metabolism in P. ostreatus IMPORTANCE Small secreted proteins (SSPs) are common in fungal saprotrophs, but their roles remain elusive. As such, they comprise part of a gene pool which may be involved in governing fungal lifestyles not limited to symbiosis and pathogenicity, in which they are commonly referred to as "effectors." We propose that Ssp1 in the white-rot fungus Pleurotus ostreatus regulates the transition from primary to secondary metabolism, development, aging, and fruiting body initiation. Our observations uncover a novel regulatory role of effector-like SSPs in a saprotroph, suggesting that they may act in fungal communication as well as in response to environmental cues. The presence of Ssp1 homologues in other fungal species supports a common potential role in environmental sensing and fungal development.

Geniposide Improves Glucose Homeostasis via Regulating FoxO1/PDK4 in Skeletal Muscle

It is well-known that imbalance state of glucose metabolism triggers many metabolic diseases and glucose uptake in skeletal muscle accounts for 90% of body weight. Geniposide is one of the major natural bioactive constituents of gardenia fruit, and the regulation of geniposide on glucose metabolism in skeletal muscle has not yet been investigated. Here, on the basis of microarray analysis, we discovered that geinposide decreased pyruvate dehydrogenase kinase 4 (PDK4) expression in skeletal muscle of mice and subsequently found that geniposide inhibited the expressions of forkhead box O1 (FoxO1), PDK4, and phosphorylated pyruvate dehydrogenase in vitro and in vivo. Moreover, geniposide promoted a switch of slow-to-fast myofiber type and glucose utilization, suggesting that geniposide improved glucose homeostasis. In addition, mechanistic studies revealed that geniposide played above roles by regulating FoxO1/PDK4, which controlled fuel selection via pyruvate dehydrogenase. Meanwhile, effects of geniposide mentioned above could be reversed by FoxO1 overexpression. Together, these results establish that geniposide confers controls on fuel usage and glucose homeostasis through FoxO1/PDK4 in skeletal muscle.

Gongronella sp. w5 elevates Coprinopsis cinerea laccase production by carbon source syntrophism and secondary metabolite induction

When sucrose was used as the carbon source, the Basidiomycete Coprinopsis cinerea showed poor growth and low laccase activity in pure culture, but greatly enhanced the level of laccase activity (>1800 U/L) during coculture with the Mucoromycete Gongronella sp. w5. As a result, the mechanism of laccase overproduction in coculture was investigated by starting from clarifying the function of sucrose. Results demonstrated that Gongronella sp. w5 in the coculture system hydrolyzed sucrose to glucose and fructose by an intracellular invertase. Fructose rather than glucose was supplied by Gongronella sp. w5  as the readily available carbon source for C. cinerea, and contributed to an alteration of its growth behavior and a basal laccase secretion of 110.6 ± 3.3 U/L. On the other hand, separating Gongronella sp. w5 of C. cinerea by transfer into dialysis tubes yielded the same level of laccase activity as without separation, indicating that enhanced laccase production probably resulted from the metabolites in the fermentation broth. Further investigation showed that the ethyl acetate-extracted metabolites generated by Gongronella sp. w5 induced C. cinerea laccase production. One of the laccase-inducing compounds namely p-hydroxybenzoic acid (HBA) was purified and identified from the extract. When using HBA as the inducer and fructose as the carbon source in monoculture, C. cinerea observed similar high laccase activity to that in coculture, and zymograms revealed the same expression of laccase Lcc9 as the main and Lcc1 and Lcc5 as the minor enzymes. Overall, our experiments verified that Gongronella sp. w5 elevates Coprinopsis cinerea laccase production by carbon source syntrophism and secondary metabolite induction.

Label-free differentially proteomic analysis of interspecific interaction between white-rot fungi highlights oxidative stress response and high metabolic activity

The laccase production by mycelial antagonistic interaction among white-rot fungi is a very important pathway for lignin degradation research. To gain a better understanding of competitive mechanisms under mycelial antagonistic interaction among three lignin-degrading white-rot basidiomycetes of Trametesversicolor (Tv), Pleurotusostreatus (Po) and Dichomitussqualens (Ds), mycelial morphology and proteins in three co-culture combinations TvPo (Tv cocultivated with Po), PoDs (Po cocultivated with Ds), TvDs (Tv cocultivated with Ds) were compared with corresponding each two mono-cultures. In this study, scanning electron microscopy detection of co-cultures indicated a highly close attachment of fungal hyphae with each other and conidiation could be inhibited under fungal interaction. In addition, a label-free proteomic analysis revealed changes on fungal proteomes existed in their counterpart competitors of co-culture. The maximum number of 1020 differentially expressed proteins (DEPs) were identified in PoDs relative to Po while the minimum number of 367 DEPs were identified in PoDs relative to Ds. Notably, we also found a large number of overexpressed proteins were oxidative stress-related proteins, followed by carbohydrate metabolism-related proteins and energy production-related proteins in all three co-culture combinations compared with control. These results were important for the future exploration of molecular mechanisms underlying lignin-degrading fungal interaction.