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Advances in genomics and transcriptomics accompanying the rapid accumulation of omics data have provided new tools that have transformed and expanded the traditional concepts of model fungi. Evolutionary genomics and transcriptomics have flourished with the use of classical and newer fungal models that facilitate the study of diverse topics encompassing fungal biology and development. Technological advances have also created the opportunity to obtain and mine large datasets. One such continuously growing dataset is that of the Sordariomycetes, which exhibit a richness of species, ecological diversity, economic importance, and a profound research history on amenable models. Currently, 3,574 species of this class have been sequenced, comprising nearly one-third of the available ascomycete genomes. Among these genomes, multiple representatives of the model genera Fusarium, Neurospora, and Trichoderma are present. In this review, we examine recently published studies and data on the Sordariomycetes that have contributed novel insights to the field of fungal evolution via integrative analyses of the genetic, pathogenic, and other biological characteristics of the fungi. Some of these studies applied ancestral state analysis of gene expression among divergent lineages to infer regulatory network models, identify key genetic elements in fungal sexual development, and investigate the regulation of conidial germination and secondary metabolism. Such multispecies investigations address challenges in the study of fungal evolutionary genomics derived from studies that are often based on limited model genomes and that primarily focus on the aspects of biology driven by knowledge drawn from a few model species. Rapidly accumulating information and expanding capabilities for systems biological analysis of Big Data are setting the stage for the expansion of the concept of model systems from unitary taxonomic species/genera to inclusive clusters of well-studied models that can facilitate both the in-depth study of specific lineages and also investigation of trait diversity across lineages. The Sordariomycetes class, in particular, offers abundant omics data and a large and active global research community. As such, the Sordariomycetes can form a core omics clade, providing a blueprint for the expansion of our knowledge of evolution at the genomic scale in the exciting era of Big Data and artificial intelligence, and serving as a reference for the future analysis of different taxonomic levels within the fungal kingdom. [ABSTRACT FROM AUTHOR]

Functional crosstalk between DNA methylation, histone H3 lysine-9 trimethylation (H3K9me3) and heterochromatin protein 1 (HP1) is essential for proper heterochromatin assembly and genome stability. However, how repressive chromatin cues guide DNA methyltransferases for region-specific DNA methylation remains largely unknown. Here, we report structure-function characterizations of DNA methyltransferase Defective-In-Methylation-2 (DIM2) in Neurospora. The DNA methylation activity of DIM2 requires the presence of both H3K9me3 and HP1. Our structural study reveals a bipartite DIM2-HP1 interaction, leading to a disorder-to-order transition of the DIM2 target-recognition domain that is essential for substrate binding. Furthermore, the structure of DIM2-HP1-H3K9me3-DNA complex reveals a substrate-binding mechanism distinct from that for its mammalian orthologue DNMT1. In addition, the dual recognition of H3K9me3 peptide by the DIM2 RFTS and BAH1 domains allosterically impacts the DIM2-substrate binding, thereby controlling DIM2-mediated DNA methylation. Together, this study uncovers how multiple heterochromatin factors coordinately orchestrate an activity-switching mechanism for region-specific DNA methylation. DIM2-mediated DNA methylation contributes to heterochromatin formation in Neurospora. This study identifies that HP1 protein and the H3K9me3 mark synergistically control DIM2 activity, providing a mechanism for heterochromatin-guided DNA methylation. [ABSTRACT FROM AUTHOR]

In the Neurospora circadian system, the White Collar Complex (WCC) formed by WC-1 and WC-2 drives expression of the frequency (frq) gene whose product FRQ feedbacks to inhibit transcriptional activity of WCC. Phosphorylation of WCC has been extensively studied, but the extent and significance of other post-translational modifications (PTM) have been poorly studied. To this end, we used mass-spectrometry to study alkylation sites on WCC, resulting in discovery of nine acetylation sites. Mutagenesis analysis showed most of the acetylation events individually do not play important roles in period determination. Moreover, mutating all the lysines falling in either half of WC-1 or all the lysine residues in WC-2 to arginines did not abolish circadian rhythms. In addition, we also found nine mono-methylation sites on WC-1, but like acetylation, individual ablation of most of the monomethylation events did not result in a significant period change. Taken together, the data here suggest that acetylation or mono-methylation on WCC is not a determinant of the pace of the circadian feedback loop. The finding is consistent with a model in which repression of WCC’s circadian activity is mainly controlled by phosphorylation. Interestingly, light induced expression of some light-responsive genes has been modulated in certain wc-1 acetylation mutants, suggesting that WC-1 acetylation events differentially regulate light responses. [ABSTRACT FROM AUTHOR]

In eukaryotes, repetitive DNA can become silenced de novo, either transcriptionally or post-transcriptionally, by processes independent of strong sequence-specific cues. The mechanistic nature of such processes remains poorly understood. We found that in the fungus Neurospora crassa, de novo initiation of both transcriptional and post-transcriptional silencing was linked to perturbed chromatin, which was produced experimentally by the aberrant activity of transcription factors at the tetO operator array. Transcriptional silencing was mediated by canonical constitutive heterochromatin. On the other hand, post-transcriptional silencing resembled repeat-induced quelling but occurred normally when homologous recombination was inactivated. All silencing of the tetO array was dependent on SAD-6, fungal ortholog of the SWI/SNF chromatin remodeler ATRX (Alpha Thalassemia/Mental Retardation Syndrome X-Linked), which was required to maintain nucleosome occupancy at the perturbed locus. In addition, we found that two other types of sequences (the lacO array and native AT-rich DNA) could also undergo recombination-independent quelling associated with perturbed chromatin. These results suggested a model in which the de novo initiation of transcriptional and post-transcriptional silencing is coupled to the remodeling of perturbed chromatin. [ABSTRACT FROM AUTHOR]

Agarwood is a resinous heartwood of Aquilaria sinensis that is formed in response to mechanical wounding. In the present study pre-treatment of Aquilaria sinensis was carried out, and then the dominant fungi were isolated and purified from the surface and electroshock holes of trees. The isolated Trichoderma sp. and Neurospora sp. were then screened for resistance against benzyl acetone and then inoculated into healthy Aquilaria sinensis trees. After six months, the agarwood was collected for analysis. The chemical composition of incense was analyzed using gas chromatography-mass spectroscopy, and 82 chemical constituents were identified. Agarwood products formed by using Trichoderma sp. and Neurospora sp. consisted of 50.22% and 48.71% ether extracts, respectively, which surpassed the 10% threshold specified by the Chinese Pharmacopoeia. Similarly, relative aromatic contents in the two agarwood products were 30.1% and 32.86%, while proportions of sesquiterpene constituents were 10.21% and 11.19%, respectively. These two agarwood-specific chemical constituents accounted for a large proportion of the total chemical composition, which showed that the generated agarwood was of good quality. The results of the study revealed that both Trichoderma sp. and Neurospora sp. were able to effectively induce agarwood production in Aquilaria sinensis trees in 6 months. This study expands the library of fungi that promote the production of agarwood from Aquilaria sinensis trees. [ABSTRACT FROM AUTHOR]

Circadian clocks temporally coordinate daily organismal biology over the 24-h cycle. Their molecular design, preserved between fungi and animals, is based on a core-oscillator composed of a one-step transcriptional-translational-negative-feedback-loop (TTFL). To test whether this evolutionarily conserved TTFL architecture is the only plausible way for achieving a functional circadian clock, we adopted a transcriptional rewiring approach, artificially co-opting regulators of the circadian output pathways into the core-oscillator. Herein we describe one of these semi-synthetic clocks which maintains all basic circadian features but, notably, it also exhibits new attributes such as a "lights-on timer" logic, where clock phase is fixed at the end of the night. Our findings indicate that fundamental circadian properties such as period, phase and temperature compensation are differentially regulated by transcriptional and posttranslational aspects of the clockworks. Synopsis: Eukaryotic circadian oscillators share a one-step transcription-translation negative-feedback loop (TTFL) circuit design, where a main transcriptional complex drives expression of a negative element that can inhibit its own expression. Here, a transcriptional rewiring strategy in the fungus N. crassa reveals that this basic circuit topology can be dramatically changed, while still yielding a functional semi-synthetic clock. Placing the transcription of the negative component frq under the control of the output promoter con-10 alters its regulation, while still yielding rhythmic expression. In the resulting functional semi-synthetic circuit, frq expression is now under the control of circadian clock downstream components. FRQ phosphorylation has a more pronounced effect on circadian period length and temperature compensation than its transcriptional regulation. In the semi-synthetic oscillator, the circadian rhythm phase is now determined by the moment the light is turned on. Co-option of downstream transcription factors into the main transcriptional circuit of the circadian clock in the fungus Neurospora crassa leads to altered clock phase determination. [ABSTRACT FROM AUTHOR]

The application of Neurospora sp., a fungus that commonly thrives on complex agricultural and plant wastes, has proven successful in utilizing citrus peel waste as a source of naringin. A UV-Vis spectrophotometric method proved the biotransformation of naringin, with an absorption maximum (λmax) observed at 310 nm for the biotransformed product, naringenin (NAR). Further verification of the conversion of naringin was provided through thin layer chromatography (TLC). The Neurospora crassa mediated biotransformation of naringin to NAR was utilized for the rapid (within 5 min) synthesis of silver (Ag) and gold (Au) nanoconjugates using sunlight to accelerate the reaction. The synthesized NAR-nano Ag and NAR-nano Au conjugates exhibited monodispersed spherical and spherical as well as polygonal shaped particles, respectively. Both of the nanoconjugates showed average particle sizes of less than 90 nm from TEM analysis. The NAR-Ag and NAR-Au nanoconjugates displayed potential enhancement of the antimicrobial activities, including antibacterial and nematicidal properties over either standalone NAR or Ag or Au NPs. This study reveals the potential of naringinase-producing Neurospora sp. for transforming naringin into NAR. Additionally, the resulting NAR-Ag and NAR-Au nanoconjugates showed promise as sustainable antibiotics and biochemical nematicides. [ABSTRACT FROM AUTHOR]

Circadian clocks drive a large array of physiological and behavioral activities. At the molecular level, circadian clocks are composed of positive and negative elements that form core oscillators generating the basic circadian rhythms. Over the course of the circadian period, circadian negative proteins undergo progressive hyperphosphorylation and eventually degrade, and their stability is finely controlled by complex post-translational pathways, including protein modifications, genetic codon preference, protein–protein interactions, chaperon-dependent conformation maintenance, degradation, etc. The effects of phosphorylation on the stability of circadian clock proteins are crucial for precisely determining protein function and turnover, and it has been proposed that the phosphorylation of core circadian clock proteins is tightly correlated with the circadian period. Nonetheless, recent studies have challenged this view. In this review, we summarize the research progress regarding the function, regulation, and mechanism of protein stability in the circadian clock systems of multiple model organisms, with an emphasis on Neurospora crassa, in which circadian mechanisms have been extensively investigated. Elucidation of the highly complex and dynamic regulation of protein stability in circadian clock networks would greatly benefit the integrated understanding of the function, regulation, and mechanism of protein stability in a wide spectrum of other biological processes. [ABSTRACT FROM AUTHOR]

Lineage-specific genes (LSGs) have long been postulated to play roles in the establishment of genetic barriers to intercrossing and speciation. In the genome of Neurospora crassa, most of the 670 Neurospora LSGs that are aggregated adjacent to the telomeres are clustered with 61% of the HET-domain genes, some of which regulate self-recognition and define vegetative incompatibility groups. In contrast, the LSG-encoding proteins possess few to no domains that would help to identify potential functional roles. Possible functional roles of LSGs were further assessed by performing transcriptomic profiling in genetic mutants and in response to environmental alterations, as well as examining gene knockouts for phenotypes. Among the 342 LSGs that are dynamically expressed during both asexual and sexual phases, 64% were detectable on unusual carbon sources such as furfural, a wildfire-produced chemical that is a strong inducer of sexual development, and the structurally-related furan 5-hydroxymethyl furfural (HMF). Expression of a significant portion of the LSGs was sensitive to light and temperature, factors that also regulate the switch from asexual to sexual reproduction. Furthermore, expression of the LSGs was significantly affected in the knockouts of adv-1 and pp-1 that regulate hyphal communication, and expression of more than one quarter of the LSGs was affected by perturbation of the mating locus. These observations encouraged further investigation of the roles of clustered lineage-specific and HET-domain genes in ecology and reproduction regulation in Neurospora, especially the regulation of the switch from the asexual growth to sexual reproduction, in response to dramatic environmental conditions changes. Author summary: A portion of genes within sequenced genomes are lineage-specific. These lineage-specific genes (LSGs) lack evolutionary histories tracking them to ancestors within the genomes of other lineages. Accordingly, they are often classified as new or de novo genes and have long been postulated to play roles in the speciation. Here 670 Neurospora LSGs are reported, most of which are aggregate adjacent to the telomeres and are clustered along with "HET-domain" genes, some of which perform functions in the regulation of self-recognition. In contrast, the LSG-encoding proteins possess few to no domains that would help to identify potential functional roles. We assessed possible functional roles of LSGs by performing transcriptomic profiling in genetic mutants and in distinct environmental conditions, as well as examining gene knockouts for phenotypes. Many LSGs are actively regulated during both asexual and sexual reproduction in response to carbon-resource, light, and temperature-based environmental factors. Furthermore, expression of the LSGs was reported to be significantly affected by perturbation of the genes adv-1, pp-1, and a mating locus that regulates hyphal communication and initiation of sexual reproduction in the fungus. These observations encouraged further investigation of the roles of clustered LSGs and HET-domain genes in ecology and reproduction regulation in Neurospora. [ABSTRACT FROM AUTHOR]

UPF-1-UPF-2-UPF-3 complex-orchestrated nonsense-mediated mRNA decay (NMD) is a well-characterized eukaryotic cellular surveillance mechanism that not only degrades aberrant transcripts to protect the integrity of the transcriptome but also eliminates normal transcripts to facilitate appropriate cellular responses to physiological and environmental changes. Here, we describe the multifaceted regulatory roles of the Neurospora crassa UPF complex in catalase-3 (cat-3) gene expression, which is essential for scavenging H2O2-induced oxidative stress. First, losing UPF proteins markedly slowed down the decay rate of cat-3 mRNA. Second, UPF proteins indirectly attenuated the transcriptional activity of cat-3 gene by boosting the decay of cpc-1 and ngf-1 mRNAs, which encode a well-studied transcription factor and a histone acetyltransferase, respectively. Further study showed that under oxidative stress condition, UPF proteins were degraded, followed by increased CPC-1 and NGF-1 activity, finally activating cat-3 expression to resist oxidative stress. Together, our data illustrate a sophisticated regulatory network of the cat-3 gene mediated by the UPF complex under physiological and H2O2-induced oxidative stress conditions. Author summary: The UPF complex-mediated NMD pathway is an evolutionarily conserved mRNA surveillance mechanism in eukaryotic cells, which degrades both mutated mRNAs to protect the transcriptome integrity and normal mRNAs to facilitate appropriate cellular responses. In fission yeast, mutant strains lacking UPF proteins are extremely sensitive to H2O2-induced oxidative stress. Here, we discovered a completely opposite H2O2-resistance mechanism in upf deletion mutants of the filamentous fungus N. crassa. Under physiological conditions, the N. crassa UPF complex inhibits the expression of the cat-3 gene to maintain redox homeostasis. In the presence of H2O2, UPF proteins are degraded and thus allow for the expression of the cat-3 gene, eventually ensuring adequate catalase activity to deal with oxidative stress. Our results do not only open up the post-transcriptional regulatory mechanism of catalase gene, but also identify the UPF complex as key node in response to oxidative stress. [ABSTRACT FROM AUTHOR]

Organisms require the ability to differentiate themselves from organisms of different or even the same species. Allorecognition processes in filamentous fungi are essential to ensure identity of an interconnected syncytial colony to protect it from exploitation and disease. Neurospora crassa has three cell fusion checkpoints controlling formation of an interconnected mycelial network. The locus that controls the second checkpoint, which allows for cell wall dissolution and subsequent fusion between cells/hyphae, cwr (cell wall remodeling), encodes two linked genes, cwr-1 and cwr-2. Previously, it was shown that cwr-1 and cwr-2 show severe linkage disequilibrium with six different haplogroups present in N. crassa populations. Isolates from an identical cwr haplogroup show robust fusion, while somatic cell fusion between isolates of different haplogroups is significantly blocked in cell wall dissolution. The cwr-1 gene encodes a putative polysaccharide monooxygenase (PMO). Herein we confirm that CWR-1 is a C1-oxidizing chitin PMO. We show that the catalytic (PMO) domain of CWR-1 was sufficient for checkpoint function and cell fusion blockage; however, through analysis of active-site, histidine-brace mutants, the catalytic activity of CWR-1 was ruled out as a major factor for allorecognition. Swapping a portion of the PMO domain (V86 to T130) did not switch cwr haplogroup specificity, but rather cells containing this chimera exhibited a novel haplogroup specificity. Allorecognition to mediate cell fusion blockage is likely occurring through a protein-protein interaction between CWR-1 with CWR-2. These data highlight a moonlighting role in allorecognition of the CWR-1 PMO domain.

The molecular mechanisms that drive circadian (24 h) rhythmicity have been investigated for many decades, but we still do not have a complete picture of eukaryotic circadian systems. Although the transcription/translation feedback loop (TTFL) model has been the primary focus of research, there are many examples of circadian rhythms that persist when TTFLs are not functioning, and we lack any good candidates for the non-TTFL oscillators driving these rhythms. In this hypothesis-driven review, the author brings together several lines of evidence pointing towards the Target of Rapamycin (TOR) signalling pathway as a good candidate for a non-TTFL oscillator. TOR is a ubiquitous regulator of metabolism in eukaryotes and recent focus in circadian research on connections between metabolism and rhythms makes TOR an attractive candidate oscillator. In this paper, the evidence for a role for TOR in regulating rhythmicity is reviewed, and the advantages of TOR as a potential oscillator are discussed. Evidence for extensive feedback regulation of TOR provides potential mechanisms for a TOR-driven oscillator. Comparison with ultradian yeast metabolic cycles provides an example of a potential TOR-driven self-sustained oscillation. Unanswered questions and problems to be addressed by future research are discussed. [ABSTRACT FROM AUTHOR]

Fungal glycosphingolipids (GSLs) are important membrane components which play a key role in vesicle trafficking. To assess the importance of GSLs in the fungal life cycle, we performed a mutant phenotypic study of the acidic and neutral GSL biosynthetic pathways in Neurospora crassa. GSL biosynthesis begins with two reactions leading up to the formation of dihydrosphingosine. The first of these reactions is catalyzed by serine palmitoyltransferase and generates 3-keto dihydrosphinganine. In N. crassa, this reaction is catalyzed by GSL-1 and GSL-2 and is required for viability. The second reaction is carried out by GSL-3, a 3-keto dihydrosphinoganine reductase to generate dihydrosphingosine, which is used for the synthesis of neutral and acidic GSLs. We found that deletion mutations in the acidic GSL pathway leading up to the formation of mannosylinositol-phosphoceramide are lethal, indicating that acidic GSLs are essential for viability in N. crassa. Once mannosylinositol-phosphoceramide is made, it is further modified by GSL-5, an inositol-phosphoceramide-B C26 hydroxylase, which adds a hydroxyl group to the amide-linked fatty acid. GSL-5 is not required for viability but gives a clear mutant phenotype affecting all stages of the life cycle. Our results show that the synthesis of mannosylinositol-phosphoceramide is required for viability and that the modification of the amide-linked fatty acid is important for acidic GSL functionality. We also examined the neutral GSL biosynthetic pathway and identified the presence of glucosylceramide. The deletion of neutral GSL biosynthetic genes affected hyphal morphology, vegetative growth rate, conidiation, and female development. Our results indicate that the synthesis of neutral GSLs is essential for normal growth and development of N. crassa. [ABSTRACT FROM AUTHOR]

In the negative feedback loop composing the Neurospora circadian clock, the core element, FREQUENCY (FRQ), binds with FRQ-interacting RNA helicase (FRH) and casein kinase 1 to form the FRQ-FRH complex (FFC) which represses its own expression by interacting with and promoting phosphorylation of its transcriptional activators White Collar-1 (WC-1) and WC-2 (together forming the White Collar complex, WCC). Physical interaction between FFC and WCC is a prerequisite for the repressive phosphorylations, and although the motif on WCC needed for this interaction is known, the reciprocal recognition motif(s) on FRQ remains poorly defined. To address this, we assessed FFC-WCC in a series of frq segmental-deletion mutants, confirming that multiple dispersed regions on FRQ are necessary for its interaction with WCC. Biochemical analysis shows that interaction between FFC and WCC but not within FFC or WCC can be disrupted by high salt, suggesting that electrostatic forces drive the association of the two complexes. As a basic sequence on WC-1 was previously identified as a key motif for WCC-FFC assembly, our mutagenetic analysis targeted negatively charged residues of FRQ, leading to identification of three Asp/Glu clusters in FRQ that are indispensable for FFC-WCC formation. Surprisingly, in several frq Asp/Glu-to-Ala mutants that vastly diminish FFC-WCC interaction, the core clock still oscillates robustly with an essentially wildtype period, indicating that the interaction between the positive and negative elements in the feedback loop is required for the operation of the circadian clock but is not a determinant of the period length. [ABSTRACT FROM AUTHOR]

Filamentous fungi undergo somatic cell fusion to create a syncytial, interconnected hyphal network which confers a fitness benefit during colony establishment. However, barriers to somatic cell fusion between genetically different cells have evolved that reduce invasion by parasites or exploitation by maladapted genetic entities (cheaters). Here, we identified a predicted mannosyltransferase, glycosyltransferase family 69 protein (GT69-2) that was required for somatic cell fusion in Neurospora crassa Cells lacking GT69-2 prematurely ceased chemotropic signaling and failed to complete cell wall dissolution and membrane merger in pairings with wild-type cells or between Δgt69-2 cells (self fusion). However, loss-of-function mutations in the linked regulator of cell fusion and cell wall remodeling-1 (rfw-1) locus suppressed the self-cell-fusion defects of Δgt69-2 cells, although Δgt69-2 Δrfw-1 double mutants still failed to undergo fusion with wild-type cells. Both GT69-2 and RFW-1 localized to the Golgi apparatus. Genetic analyses indicated that RFW-1 negatively regulates cell wall remodeling-dependent processes, including cell wall dissolution during cell fusion, separation of conidia during asexual sporulation, and conidial germination. GT69-2 acts as an antagonizer to relieve or prevent negative functions on cell fusion by RFW-1. In Neurospora species and N. crassa populations, alleles of gt69-2 were highly polymorphic and fell into two discrete haplogroups. In all isolates within haplogroup I, rfw-1 was conserved and linked to gt69-2 All isolates within haplogroup II lacked rfw-1. These data indicated that gt69-2/rfw-1 are under balancing selection and provide new mechanisms regulating cell wall remodeling during cell fusion and conidial separation.IMPORTANCE Cell wall remodeling is a dynamic process that balances cell wall integrity versus cell wall dissolution. In filamentous fungi, cell wall dissolution is required for somatic cell fusion and conidial separation during asexual sporulation. In the filamentous fungus Neurospora crassa, allorecognition checkpoints regulate the cell fusion process between genetically different cells. Our study revealed two linked loci with transspecies polymorphisms and under coevolution, rfw-1 and gt69-2, which form a coordinated system to regulate cell wall remodeling during somatic cell fusion, conidial separation, and asexual spore germination. RFW-1 acts as a negative regulator of these three processes, while GT69-2 functions antagonistically to RFW-1. Our findings provide new insight into the mechanisms involved in regulation of fungal cell wall remodeling during growth and development.

Codon usage bias is a fundamental feature of all genomes and plays an important role in determining gene expression levels. The codon usage was thought to influence gene expression mainly due to its impact on translation. Recently, however, codon usage was shown to affect transcription of fungal and mammalian genes, indicating the existence of a gene regulatory phenomenon with unknown mechanism. In Neurospora, codon usage biases strongly correlate with mRNA levels genome-wide, and here we show that the correlation between codon usage and RNA levels is maintained in the nucleus. In addition, codon optimality is tightly correlated with both total and nuclear RNA levels, suggesting that codon usage broadly influences mRNA levels through transcription in a translation-independent manner. A large-scale RNA sequencing-based genetic screen in Neurospora identified 18 candidate factors that when deleted decreased the genome-wide correlation between codon usage and RNA levels and reduced the codon usage effect on gene expression. Most of these factors, such as the H3K36 methyltransferase, are chromatin regulators or transcription factors. Together, our results suggest that the transcriptional effect of codon usage is mediated by multiple transcriptional regulatory mechanisms.

A correction is presented to the article "The Sordariomycetes: An Expanding Resource With Big Data for Mining in Evolutionary Genomics and Transcriptomics," which appeared in the 2023 issue of the magazine.

BackgroundWith 9730 protein-coding genes and a nearly complete gene knockout strain collection, Neurospora crassa is a major model organism for filamentous fungi. Despite this abundance of information, the phenotypes of these gene knockout mutants have not been categorized to determine whether there are broad correlations between phenotype and any genetic features.ResultsHere, we analyze data for 10 different growth or developmental phenotypes that have been obtained for 1168 N. crassa knockout mutants. Of these mutants, 265 (23%) are in the normal range, while 903 (77%) possess at least one mutant phenotype. With the exception of unclassified functions, the distribution of functional categories for genes in the mutant dataset mirrors that of the N. crassa genome. In contrast, most genes do not possess a yeast ortholog, suggesting that our analysis will reveal functions that are not conserved in Saccharomyces cerevisiae. To leverage the phenotypic data to identify pathways, we used weighted Partitioning Around Medoids (PAM) approach with 40 clusters. We found that genes encoding metabolic, transmembrane and protein phosphorylation-related genes are concentrated in subsets of clusters. Results from K-Means clustering of transcriptomic datasets showed that most phenotypic clusters contain multiple expression profiles, suggesting that co-expression is not generally observed for genes with shared phenotypes. Analysis of yeast orthologs of genes that co-clustered in MAPK signaling cascades revealed potential networks of interacting proteins in N. crassa.ConclusionsOur results demonstrate that clustering analysis of phenotypes is a promising tool for generating new hypotheses regarding involvement of genes in cellular pathways in N. crassa. Furthermore, information about gene clusters identified in N. crassa should be applicable to other filamentous fungi, including saprobes and pathogens.

The circadian clock of Neurospora crassa is based on a negative transcriptional/translational feedback loops. The frequency (frq) gene controls the morning-specific rhythmic transcription of a sense RNA encoding FRQ, the negative element of the core circadian feedback loop. In addition, a long noncoding antisense RNA, qrf, is rhythmically transcribed in an evening-specific manner. It has been reported that the qrf rhythm relies on transcriptional interference with frq transcription and that complete suppression of qrf transcription impairs the circadian clock. We show here that qrf transcription is dispensable for circadian clock function. Rather, the evening-specific transcriptional rhythm of qrf is mediated by the morning-specific repressor CSP-1. Since CSP-1 expression is induced by light and glucose, this suggests a rhythmic coordination of qrf transcription with metabolism. However, a possible physiological significance for the circadian clock remains unclear, as suitable assays are not available. [ABSTRACT FROM AUTHOR]

Objective: This study analyzes the mycobiome in wild and captive Sumatran orangutans. Materials and Methods: Nine orangutan feces samples from the wild and nine from captivity were divided into three repeats from 11- to 15-year-olds in good health. The Illumina platform for analysis of ITS bioinformatics was used according to the Qiime2 and CCMetagen approaches. Results: Wild Sumatran orangutans include 53% Ascomycota, 38% uncultured fungi, and 4% Basidiomycota. Orangutans in captivity are 57% Ascomycota, 26% uncultured fungi, and 2% Basidiomycota. Based on genuslevel, uncultured Neurospora (31%), Penicillium (10%), Aspergillus (3%), Fusarium (3%), Candida (2%), Cutaneotrichosporon (2%), and Limonomyces (2%) are found in wild orangutans. The most prevalent genus among captivity orangutans is Aspergillus (32%), followed by fungal sp. (11%), Lasiodiplodia (18%), Devriesia (2%), and Sordariomycetes (2%). According to the Chao1 diversity index and Shannon and Simpson, there was no significant difference between wild and captive Sumatran orangutans. Conclusion: Neurospora is unique to wild Sumatran orangutans, although Aspergillus predominates in captive orangutans. We hypothesize that the gut mycobiome of wild orangutans will resemble that of orangutans in captivity. The excellent range of food sources in the forest does not result in the prevalence of fungi in the typical gut microbiome. [ABSTRACT FROM AUTHOR]

The hyphal tips of Neurospora crassa have prevacuolar compartments (PVCs) of unusual size and shape. They appear to function as late endosomes/multivesicular bodies. PVCs are highly variable in size (1–3 microns) and exhibit rapid changes in structure. When visualized with tagged integral membrane proteins of the vacuole the PVCs appear as ring or horseshoe-shaped structures. Some soluble molecules that fill the lumen of mature spherical vacuoles do not appear in the lumen of the PVC but are seen in the ring or horseshoe-shaped structures. By using super-resolution microscopy I have achieved a better understanding of the structure of the PVCs. The PVC appears to form a pouch with an open end. The walls of the pouch are composed of small vesicles or tubules, approximately 250 nm in diameter. The shape of the PVC can change in a few seconds, caused by the apparent movement of the vesicles/tubules. In approximately 85% of the PVCs dynein and dynactin were observed as poorly defined lumps inside the pouch-shaped PVCs. Within the PVCs they were not attached to microtubules nor did they appear to be in direct contact with the vesicles and tubules that formed the PVCs. In the future, the structure and relatively large size of the Neurospora PVC may allow us to visualize protein-sorting events that occur in the formation of vacuoles. [ABSTRACT FROM AUTHOR]

Context: Agricultural by-products such as grape pomace (GP), could form an important component of ruminant diets. Aims: The present study aimed to evaluate the effects of treating GP with Neurospora sitophila on chemical composition, digestibility, nitrogen balance, rumen, and blood parameters. Methods: Twenty-four adult Kermani rams were allocated to one of three treatments arranged as a completely randomised design for a 26-day period. The first 21 days were for adaptation, and the last 5 days were for sample collection. The animals were placed in individual cages equipped with a urine–faeces separator. They were fed with (1) a basal diet without GP (control), (2) a basal diet with 20% of untreated grape pomace (UGP), and (3) a basal diet with 20% of N. sitophila -treated grape pomace (TGP). Key results: Treating GP increased the percentages of crude protein (CP), lignin and rumen-degradable protein (RDP; P < 0.01), but decreased rumen-undegradable protein (RUP; P < 0.05) and total phenols and tannins (P < 0.01). Nutrient digestibility in the TGP- and UGP-supplemented groups was lower than that in the control group (P < 0.05). The mean excretion of allantoin (P < 0.05), xanthine plus hypoxanthine (P < 0.01), total purine derivatives (P < 0.05), and microbial protein synthesis (P < 0.05) were lower in the sheep fed UGP than in the control group. The acetate (P < 0.01), propionate and total volatile fatty acids (P < 0.05) in rumen fluid were the highest in the control group. The UGP-supplemented group had a higher rumen pH and a lower NH3-N concentration than did other groups, 1.5 h after feed intake. Also, blood glucose and urea nitrogen in animals fed UGP were lower than in those in other groups (P < 0.05). Conclusions: Treating of GP with N. sitophila fungus increases the CP and RDP and reduces the adverse effects of GP on ruminal kinetics. Implications: The GP that has been exposed and treated with N. sitophila may provide a suitable supplementary feed for ruminants when incorporated into diets at rates of up to 20%. Utilisation of the by-products in the animal nutrition results in less consumption of cereal grain by animals. These by-products, such as grape pomace (GP), could form an important component of ruminant diets. The GP is being produced after extracting juice that is not used by humans or industries. Results showed that GP that has been exposed and treated with Neurospora sitophila may provide a suitable supplementary feed for ruminants when incorporated into diets at rates of up to 20%. [ABSTRACT FROM AUTHOR]

Neurospora crassa is an important model organism for circadian clock research. The Neurospora core circadian component FRQ protein has two isoforms, large FRQ (l-FRQ) and small FRQ (s-FRQ), of which l-FRQ bears an additional Nterminal 99-amino acid fragment. However, how the FRQ isoforms operate differentially in regulating the circadian clock remains elusive. Here, we show l-FRQ and s-FRQ play different roles in regulating the circadian negative feedback loop. Compared to s-FRQ, l-FRQ is less stable and undergoes hypophosphorylation and faster degradation. The phosphorylation of the C-terminal l-FRQ 794-aa fragment was markedly higher than that of s-FRQ, suggesting the l-FRQ N-terminal 99-aa region may regulate the phosphorylation of the entire FRQ protein. Quantitative label-free LC/MS analysis identified several peptides that were differentially phosphorylated between l-FRQ and s-FRQ, which were distributed in FRQ in an interlaced fashion. Furthermore, we identified two novel phosphorylation sites, S765 and T781; mutations S765A and T781A showed no significant effects on conidiation rhythmicity, although T781 conferred FRQ stability. These findings demonstrate that FRQ isoforms play differential roles in the circadian negative feedback loop and undergo different regulations of phosphorylation, structure, and stability. The l-FRQ N-terminal 99-aa region plays an important role in regulating the phosphorylation, stability, conformation, and function of the FRQ protein. As the FRQ circadian clock counterparts in other species also have isoforms or paralogues, these findings will also further our understanding of the underlying regulatory mechanisms of the circadian clock in other organisms based on the high conservation of circadian clocks in eukaryotes. [ABSTRACT FROM AUTHOR]

Programmed cell death (PCD) in filamentous fungi prevents cytoplasmic mixing following fusion between conspecific genetically distinct individuals (allorecognition) and serves as a defense mechanism against mycoparasitism, genome exploitation, and deleterious cytoplasmic elements (i.e., senescence plasmids). Recently, we identified regulatorof cell death-1 (rcd-1), a gene controlling PCD in germinated asexual spores in the filamentous fungus Neurospora crassarcd-1 alleles are highly polymorphic and fall into two haplogroups in N. crassa populations. Coexpression of alleles from the two haplogroups, rcd-1-1 and rcd-1-2, is necessary and sufficient to trigger a cell death reaction. Here, we investigated the molecular bases of rcd-1-dependent cell death. Based on in silico analyses, we found that RCD-1 is a remote homolog of the N-terminal pore-forming domain of gasdermin, the executioner protein of a highly inflammatory cell death reaction termed pyroptosis, which plays a key role in mammalian innate immunity. We show that RCD-1 localizes to the cell periphery and that cellular localization of RCD-1 was correlated with conserved positively charged residues on predicted amphipathic α-helices, as shown for murine gasdermin-D. Similar to gasdermin, RCD-1 binds acidic phospholipids in vitro, notably, cardiolipin and phosphatidylserine, and interacts with liposomes containing such lipids. The RCD-1 incompatibility system was reconstituted in human 293T cells, where coexpression of incompatible rcd-1-1/rcd-1-2 alleles triggered pyroptotic-like cell death. Oligomers of RCD-1 were associated with the cell death reaction, further supporting the evolutionary relationship between gasdermin and rcd-1 This report documents an ancient transkingdom relationship of cell death execution modules involved in organismal defense.

Filamentous fungi are intensively used for producing industrial enzymes, including lignocellulases. Employing insoluble cellulose to induce the production of lignocellulases causes some drawbacks, e.g., a complex fermentation operation, which can be overcome by using soluble inducers such as cellobiose. Here, a triple β-glucosidase mutant of Neurospora crassa, which prevents rapid turnover of cellobiose and thus allows the disaccharide to induce lignocellulases, was applied to profile the proteome responses to cellobiose and cellulose (Avicel). Our results revealed a shared proteomic response to cellobiose and Avicel, whose elements included lignocellulases and cellulolytic product transporters. While the cellulolytic proteins showed a correlated increase in protein and mRNA levels, only a moderate correlation was observed on a proteomic scale between protein and mRNA levels (R2 = 0.31). Ribosome biogenesis and rRNA processing were significantly overrepresented in the protein set with increased protein but unchanged mRNA abundances in response to Avicel. Ribosome biogenesis, as well as protein processing and protein export, was also enriched in the protein set that showed increased abundance in response to cellobiose. NCU05895, a homolog of yeast CWH43, is potentially involved in transferring a glycosylphosphatidylinositol (GPI) anchor to nascent proteins. This protein showed increased abundance but no significant change in mRNA levels. Disruption of CWH43 resulted in a significant decrease in cellulase activities and secreted protein levels in cultures grown on Avicel, suggesting a positive regulatory role for CWH43 in cellulase production. The findings should have an impact on a systems engineering approach for strain improvement for the production of lignocellulases.IMPORTANCE Lignocellulases are important industrial enzymes for sustainable production of biofuels and bio-products. Insoluble cellulose has been commonly used to induce the production of lignocellulases in filamentous fungi, which causes a difficult fermentation operation and enzyme loss due to adsorption to cellulose. The disadvantages can be overcome by using soluble inducers, such as the disaccharide cellobiose. Quantitative proteome profiling of the model filamentous fungus Neurospora crassa revealed cellobiose-dependent pathways for cellulase production, including protein processing and export. A protein (CWH43) potentially involved in protein processing was found to be a positive regulator of lignocellulase production. The cellobiose-dependent mechanisms provide new opportunities to improve the production of lignocellulases in filamentous fungi.

Nonself recognition following cell fusion between genetically distinct individuals of the same species in filamentous fungi often results in a programmed cell death (PCD) reaction, where the heterokaryotic fusion cell is compartmentalized and rapidly killed. The allorecognition process plays a key role as a defense mechanism that restricts genome exploitation, resource plundering, and the spread of deleterious senescence plasmids and mycoviruses. Although a number of incompatibility systems have been described that function in mature hyphae, less is known about the PCD pathways in asexual spores, which represent the main infectious unit in various human and plant fungal pathogens. Here, we report the identification of regulator of cell death-1 (rcd-1), a novel allorecognition gene, controlling PCD in germinating asexual spores of Neurospora crassa; rcd-1 is one of the most polymorphic genes in the genomes of wild N. crassa isolates. The coexpression of two antagonistic rcd-1-1 and rcd-1-2 alleles was necessary and sufficient to trigger cell death in fused germlings and in hyphae. Based on analysis of wild populations of N. crassa and N. discreta, rcd-1 alleles appeared to be under balancing selection and associated with trans-species polymorphisms. We shed light on genomic rearrangements that could have led to the emergence of the incompatibility system in Neurospora and show that rcd-1 belongs to a much larger gene family in fungi. Overall, our work contributes toward a better understanding of allorecognition and PCD in an underexplored developmental stage of filamentous fungi.

The white collar proteins WC1 and WC2 interact with each other to form a white collar complex acting as a well-known transcription regulator required for the operation of the circadian clock in Neurospora, but their roles in insect-pathogenic fungal lifecycles remain poorly understood. Here, we report that WC1 and WC2 orthologs co-regulate the conidiation capacity and conidial resistance to solar ultraviolet-B (UVB) irradiation in Beauveria bassiana, after their high activities in the photorepair of UVB-induced DNA damages were elucidated previously in the insect mycopathogen, which features non-rhythmic conidiation and high conidiation capacity. The conidial yield, UVB resistance, and photoreactivation rate of UVB-impaired conidia were greatly reduced in the null mutants of wc1 and wc2 compared to their control strains. However, many other lifecycle-related phenotypes, except the antioxidant response, were rarely affected in the two mutants. Transcriptomic analysis revealed largely overlapping roles for WC1 and WC2 in regulating the fungal gene networks. Most of the differentially expressed genes identified from the null mutants of wc1 (1380) and wc2 (1001) were co-downregulated (536) or co-upregulated (256) at similar levels, including several codownregulated genes required for aerial conidiation and DNA photorepair. These findings expand a molecular basis underlying the fungal adaptation to solar UV irradiation and offer a novel insight into the genome-wide co-regulatory roles of WC1 and WC2 in B. bassiana's asexual development and in vivo photoreactivation against solar UV damage. [ABSTRACT FROM AUTHOR]

In the negative feedback loop driving the Neurospora circadian oscillator, the negative element, FREQUENCY (FRQ), inhibits its own expression by promoting phosphorylation of its heterodimeric transcriptional activators, White Collar-1 (WC-1) and WC-2. FRQ itself also undergoes extensive time-of-day-specific phosphorylation with over 100 phosphosites previously documented. Although disrupting individual or certain clusters of phosphorylation sites has been shown to alter circadian period lengths to some extent, it is still elusive how all the phosphorylations on FRQ control its activity. In this study, we systematically investigated the role in period determination of all 110 reported FRQ phosphorylation sites, using mutagenesis and luciferase reporter assays. Surprisingly, robust FRQ phosphorylation is still detected even when 84 phosphosites were eliminated altogether; further mutating another 26 phosphoresidues completely abolished FRQ phosphorylation. To identify phosphoresidue(s) on FRQ impacting circadian period length, a series of clustered frq phosphomutants covering all the 110 phosphosites were generated and examined for period changes. When phosphosites in the N-terminal and middle regions of FRQ were eliminated, longer periods were typically seen while removal of phosphorylation in the C-terminal tail resulted in extremely short periods, among the shortest reported. Interestingly, abolishing the 11 phosphosites in the C-terminal tail of FRQ not only results in an extremely short period, but also impacts temperature compensation (TC), yielding an overcompensated circadian oscillator. In addition, the few phosphosites in the middle of FRQ are also found to be crucial for TC. When different groups of FRQ phosphomutations were combined intramolecularly, expected additive effects were generally observed except for one novel case of intramolecular epistasis, where arrhythmicity resulting from one cluster of phosphorylation site mutants was restored by eliminating phosphorylation at another group of sites. [ABSTRACT FROM AUTHOR]

The endophytic fungus Neurospora dictyophora 3ZF‐02 with a special aroma was isolated from the arils of Torreya grandis. Analysis of volatile organic compounds was done by gas chromatography–mass spectrometry. A total of 46 compounds were identified in the volatile organic compounds by 3ZF‐02. In the growth phase, esters, acids, along with some alcohols and ketones were the main components. During the recession period, a large amount of benzene and naphthalene compounds appeared, accompanied by the production of amines. Oleic acid, methyl abietate, terpinen‐4‐ol were also found. They were the same ingredients in essential oil of Torreya. The antioxidant activity and antifungal activity of all extracts were also evaluated. When cultured for 10 days, it exhibited the most significant antioxidant activity with IC50 of 1.44 and 0.95 g/L against diphenyl picryl hydrazinyl and hydroxyl radicals, respectively. In addition, the extracts cultured for 10 days exhibited the most significant antifungal activity against Candida albicans with minimum inhibitory concentration 1.56 mg/ml. [ABSTRACT FROM AUTHOR]

Advances in genomics and transcriptomics accompanying the rapid accumulation of omics data have provided new tools that have transformed and expanded the traditional concepts of model fungi. Evolutionary genomics and transcriptomics have flourished with the use of classical and newer fungal models that facilitate the study of diverse topics encompassing fungal biology and development. Technological advances have also created the opportunity to obtain and mine large datasets. One such continuously growing dataset is that of the Sordariomycetes, which exhibit a richness of species, ecological diversity, economic importance, and a profound research history on amenable models. Currently, 3,574 species of this class have been sequenced, comprising nearly one-third of the available ascomycete genomes. Among these genomes, multiple representatives of the model genera Fusarium, Neurospora, and Trichoderma are present. In this review, we examine recently published studies and data on the Sordariomycetes that have contributed novel insights to the field of fungal evolution via integrative analyses of the genetic, pathogenic, and other biological characteristics of the fungi. Some of these studies applied ancestral state analysis of gene expression among divergent lineages to infer regulatory network models, identify key genetic elements in fungal sexual development, and investigate the regulation of conidial germination and secondary metabolism. Such multispecies investigations address challenges in the study of fungal evolutionary genomics derived from studies that are often based on limited model genomes and that primarily focus on the aspects of biology driven by knowledge drawn from a few model species. Rapidly accumulating information and expanding capabilities for systems biological analysis of Big Data are setting the stage for the expansion of the concept of model systems from unitary taxonomic species/genera to inclusive clusters of well-studied models that can facilitate both the in-depth study of specific lineages and also investigation of trait diversity across lineages. The Sordariomycetes class, in particular, offers abundant omics data and a large and active global research community. As such, the Sordariomycetes can form a core omics clade, providing a blueprint for the expansion of our knowledge of evolution at the genomic scale in the exciting era of Big Data and artificial intelligence, and serving as a reference for the future analysis of different taxonomic levels within the fungal kingdom.

Cell-to-cell communication and cell fusion are fundamental biological processes across the tree of life. Survival is often dependent upon being able to identify nearby individuals and respond appropriately. Communication between genetically different individuals allows for the identification of potential mating partners, symbionts, prey, or predators. In contrast, communication between genetically similar (or identical) individuals is important for mediating the development of multicellular organisms or for coordinating density-dependent behaviors (i.e., quorum sensing). This review describes the molecular and genetic mechanisms that mediate cell-to-cell communication and cell fusion between cells of Ascomycete filamentous fungi, with a focus on Neurospora crassa. Filamentous fungi exist as a multicellular, multinuclear network of hyphae, and communication-mediated cell fusion is an important aspect of colony development at each stage of the life cycle. Asexual spore germination occurs in a density-dependent manner. Germinated spores (germlings) avoid cells that are genetically different at specific loci, while chemotropically engaging with cells that share identity at these recognition loci. Germlings with genetic identity at recognition loci undergo cell fusion when in close proximity, a fitness attribute that contributes to more rapid colony establishment. Communication and cell fusion also occur between hyphae in a colony, which are important for reinforcing colony architecture and supporting the development of complex structures such as aerial hyphae and sexual reproductive structures. Over 70 genes have been identified in filamentous fungi (primarily N. crassa) that are involved in kind recognition, chemotropic interactions, and cell fusion. While the hypothetical signal(s) and receptor(s) remain to be described, a dynamic molecular signaling network that regulates cell-cell interactions has been revealed, including two conserved MAP-Kinase cascades, a conserved STRIPAK complex, transcription factors, a NOX complex involved in the generation of reactive oxygen species, cell-integrity sensors, actin, components of the secretory pathway, and several other proteins. Together these pathways facilitate the integration of extracellular signals, direct polarized growth, and initiate a transcriptional program that reinforces signaling and prepares cells for downstream processes, such as membrane merger, cell fusion and adaptation to heterokaryon formation.

Transcriptional and translational feedback loops in fungi and animals drive circadian rhythms in transcript levels that provide output from the clock, but post-transcriptional mechanisms also contribute. To determine the extent and underlying source of this regulation, we applied newly developed analytical tools to a long-duration, deeply sampled, circadian proteomics time course comprising half of the proteome. We found a quarter of expressed proteins are clock regulated, but >40% of these do not arise from clock-regulated transcripts, and our analysis predicts that these protein rhythms arise from oscillations in translational rates. Our data highlighted the impact of the clock on metabolic regulation, with central carbon metabolism reflecting both transcriptional and post-transcriptional control and opposing metabolic pathways showing peak activities at different times of day. The transcription factor CSP-1 plays a role in this metabolic regulation, contributing to the rhythmicity and phase of clock-regulated proteins.

Filamentous fungus biomass is a protein-rich food, which can serve as an alternative to animal, plant, and legume protein sources. Neurospora crassa is a filamentous fungus that typically grows in tropical and sub-tropical regions. Traditionally, N. crassa has served as a model eukaryotic organism due to its ease of growth and propagation and suitability for genetic manipulation. However, filamentous fungi, such as Neurospora, have also been consumed or used to produce fermented foods for centuries and have been developed into protein-rich biomass ingredients to be used in conventional foods and meat substitutes. A panel of toxicological tests including genotoxic, acute, and subchronic studies were conducted on dried N. crassa biomass to support its safe use in food. The dried N. crassa biomass was found to be not genotoxic in a bacterial reverse mutation (Ames) assay, an in vitro chromosomal aberration test, and an in vivo micronucleus test. In the acute and subchronic toxicity studies, rats were orally gavaged with N. crassa biomass at concentrations of 0, 1,000, 2,500, and 5,000 mg/kg body weight/day for 14 and 90 days, respectively. At the conclusion of the studies, there were no test article-related toxicity results observed in clinical observations, body weight, food consumption, ophthalmology, hematology, clinical chemistry, coagulation, thyroid hormone, urinalysis, and macroscopic and microscopic findings. The no-observed-adverse-effect level for the dried N. crassa biomass ingredient was determined to be 5,000 mg/kg body weight/day, the highest dose tested. [ABSTRACT FROM AUTHOR]

Evolution of Bateson‐Dobzhansky‐Muller (BDM) incompatibilities is thought to represent a key step in the formation of separate species. They are incompatible alleles that have evolved in separate populations and are exposed in hybrid offspring as hybrid sterility or lethality. In this study, we reveal a previously unconsidered mechanism promoting the formation of BDM incompatibilities, meiotic drive. Theoretical studies have evaluated the role that meiotic drive, the phenomenon whereby selfish elements bias their transmission to progeny at ratios above 50:50, plays in speciation, and have mostly concluded that drive could not result in speciation on its own. Using the model fungus Neurospora, we demonstrate that the large meiotic drive haplotypes, Sk‐2 and Sk‐3, contain putative sexual incompatibilities. Our experiments revealed that although crosses between Neurospora intermedia and Neurospora metzenbergii produce viable progeny at appreciable rates, when strains of N. intermedia carry Sk‐2 or Sk‐3 the proportion of viable progeny drops substantially. Additionally, it appears that Sk‐2 and Sk‐3 have accumulated different incompatibility phenotypes, consistent with their independent evolutionary history. This research illustrates how meiotic drive can contribute to reproductive isolation between populations, and thereby speciation. [ABSTRACT FROM AUTHOR]

Heterotrimeric (αβγ) G protein signaling pathways are critical environmental sensing systems found in eukaryotic cells. Exchange of GDP for GTP on the Gα subunit leads to its activation. In contrast, GTP hydrolysis on the Gα is accelerated by Regulator of G protein Signaling (RGS) proteins, resulting in a return to the GDP-bound, inactive state. Here, we analyzed growth, development and extracellular cellulase production in strains with knockout mutations in the seven identified RGS genes (rgs-1 to rgs-7) in the filamentous fungus, Neurospora crassa. We compared phenotypes to those of strains with either knockout mutations or expressing predicted constitutively activated, GTPase-deficient alleles for each of the three Gα subunit genes (gna-1Q204L, gna-2Q205L or gna-3Q208L). Our data revealed that six RGS mutants have taller aerial hyphae than wild type and all seven mutants exhibit reduced asexual sporulation, phenotypes shared with strains expressing the gna-1Q204L or gna-3Q208L allele. In contrast, Δrgs-1 and Δrgs-3 were the only RGS mutants with a slower growth rate phenotype, a defect in common with gna-1Q204L strains. With respect to female sexual development, Δrgs-1 possessed defects most similar to gna-3Q208L strains, while those of Δrgs-2 mutants resembled strains expressing the gna-1Q204L allele. Finally, we observed that four of the seven RGS mutants had significantly different extracellular cellulase levels relative to wild type. Of interest, the Δrgs-2 mutant had no detectable activity, similar to the gna-3Q208L strain. In contrast, the Δrgs-1 and Δrgs-4 mutants and gna-1Q204L and gna-2Q205L strains exhibited significantly higher cellulase activity than wild type. With the exception of sexual development, our results demonstrate the greatest number of genetic interactions between rgs-1 and gna-1 and rgs-2 and gna-3 in N. crassa. [ABSTRACT FROM AUTHOR]

• Neurospora intermedia has the potential to cause an endobronchial mass. • N. intermedia develops orange conidiating colonies composed of septate hyphae. • Coculturing opposite mating types yields ascomata, indicating heterothallism. • N. intermedia cross-reacts with the Aspergillus galactomannan assay in vitro. • N. intermedia is susceptible to amphotericin B and voriconazole. The ascomycete filamentous fungus Neurospora intermedia is commonly used in the food industry and considered nonpathogenic to humans. This study characterizes four N. intermedia isolates recovered from three patients. The first patient had a mediastinal germ cell tumor with multiple metastases. N. intermedia was recovered from his endotracheal aspirate and from the endobronchial mass obtained by bronchoscopic forceps biopsy. Histopathology of the biopsy tissue revealed necrotic tissue mixed with septate fungal hyphae with right-angle branching. An endobronchial mass caused by N. intermedia was thus diagnosed. Another two N. intermedia isolates were recovered from the endotracheal aspirates of two critically ill patients. In vitro, N. intermedia grows rapidly and forms orange, conidiating colonies composed of septate hyphae. Two isolates from the first patient belong to mating type a; the other two isolates belong to mating type A. Coculture of isolates of opposite mating types yielded dark ascomata containing ascospores, supporting that N. intermedia is a heterothallic fungus. N. intermedia isolates cross-reacted with the Aspergillus galactomannan antigen assay and were susceptible to amphotericin B and voriconazole. In conclusion, this report describes the first human infection (endobronchial mass) caused by N. intermedia , highlighting its potential to invade the human respiratory tract. [ABSTRACT FROM AUTHOR]

The molecular mechanisms that drive circadian (24 h) rhythmicity have been investigated for many decades, but we still do not have a complete picture of eukaryotic circadian systems. Although the transcription/translation feedback loop (TTFL) model has been the primary focus of research, there are many examples of circadian rhythms that persist when TTFLs are not functioning, and we lack any good candidates for the non-TTFL oscillators driving these rhythms. In this hypothesis-driven review, the author brings together several lines of evidence pointing towards the Target of Rapamycin (TOR) signalling pathway as a good candidate for a non-TTFL oscillator. TOR is a ubiquitous regulator of metabolism in eukaryotes and recent focus in circadian research on connections between metabolism and rhythms makes TOR an attractive candidate oscillator. In this paper, the evidence for a role for TOR in regulating rhythmicity is reviewed, and the advantages of TOR as a potential oscillator are discussed. Evidence for extensive feedback regulation of TOR provides potential mechanisms for a TOR-driven oscillator. Comparison with ultradian yeast metabolic cycles provides an example of a potential TOR-driven self-sustained oscillation. Unanswered questions and problems to be addressed by future research are discussed.

Fungal glycosphingolipids (GSLs) are important membrane components which play a key role in vesicle trafficking. To assess the importance of GSLs in the fungal life cycle, we performed a mutant phenotypic study of the acidic and neutral GSL biosynthetic pathways in Neurospora crassa. GSL biosynthesis begins with two reactions leading up to the formation of dihydrosphingosine. The first of these reactions is catalyzed by serine palmitoyltransferase and generates 3-keto dihydrosphinganine. In N. crassa, this reaction is catalyzed by GSL-1 and GSL-2 and is required for viability. The second reaction is carried out by GSL-3, a 3-keto dihydrosphinoganine reductase to generate dihydrosphingosine, which is used for the synthesis of neutral and acidic GSLs. We found that deletion mutations in the acidic GSL pathway leading up to the formation of mannosylinositol-phosphoceramide are lethal, indicating that acidic GSLs are essential for viability in N. crassa. Once mannosylinositol-phosphoceramide is made, it is further modified by GSL-5, an inositol-phosphoceramide-B C26 hydroxylase, which adds a hydroxyl group to the amide-linked fatty acid. GSL-5 is not required for viability but gives a clear mutant phenotype affecting all stages of the life cycle. Our results show that the synthesis of mannosylinositol-phosphoceramide is required for viability and that the modification of the amide-linked fatty acid is important for acidic GSL functionality. We also examined the neutral GSL biosynthetic pathway and identified the presence of glucosylceramide. The deletion of neutral GSL biosynthetic genes affected hyphal morphology, vegetative growth rate, conidiation, and female development. Our results indicate that the synthesis of neutral GSLs is essential for normal growth and development of N. crassa.

The magnitude and direction of carbon cycle feedbacks under climate warming remain uncertain due to insufficient knowledge about the temperature sensitivities of soil microbial processes. Enzymatic rates could increase at higher temperatures, but this response could change over time if soil microbes adapt to warming. We used the Arrhenius relationship, biochemical transition state theory, and thermal physiology theory to predict the responses of extracellular enzyme Vmax and Km to temperature. Based on these concepts, we hypothesized that Vmax and Km would correlate positively with each other and show positive temperature sensitivities. For enzymes from warmer environments, we expected to find lower Vmax , Km , and Km temperature sensitivity but higher Vmax temperature sensitivity. We tested these hypotheses with isolates of the filamentous fungus Neurospora discreta collected from around the globe and with decomposing leaf litter from a warming experiment in Alaskan boreal forest. For Neurospora extracellular enzymes, Vmax Q10 ranged from 1.48 to 2.25, and Km Q10 ranged from 0.71 to 2.80. In agreement with theory, Vmax and Km were positively correlated for some enzymes, and Vmax declined under experimental warming in Alaskan litter. However, the temperature sensitivities of Vmax and Km did not vary as expected with warming. We also found no relationship between temperature sensitivity of Vmax or Km and mean annual temperature of the isolation site for Neurospora strains. Declining Vmax in the Alaskan warming treatment implies a short-term negative feedback to climate change, but the Neurospora results suggest that climate-driven changes in plant inputs and soil properties are important controls on enzyme kinetics in the long term. Our empirical data on enzyme Vmax , Km , and temperature sensitivities should be useful for parameterizing existing biogeochemical models, but they reveal a need to develop new theory on thermal adaptation mechanisms.

In plants and metazoans, intracellular receptors that belong to the NOD-like receptor (NLR) family are major contributors to innate immunity. Filamentous fungal genomes contain large repertoires of genes encoding for proteins with similar architecture to plant and animal NLRs with mostly unknown function. Here, we identify and molecularly characterize patatin-like phospholipase-1 (PLP-1), an NLR-like protein containing an N-terminal patatin-like phospholipase domain, a nucleotide-binding domain (NBD), and a C-terminal tetratricopeptide repeat (TPR) domain. PLP-1 guards the essential SNARE protein SEC-9; genetic differences at plp-1 and sec-9 function to trigger allorecognition and cell death in two distantly related fungal species, Neurospora crassa and Podospora anserina Analyses of Neurospora population samples revealed that plp-1 and sec-9 alleles are highly polymorphic, segregate into discrete haplotypes, and show transspecies polymorphism. Upon fusion between cells bearing incompatible sec-9 and plp-1 alleles, allorecognition and cell death are induced, which are dependent upon physical interaction between SEC-9 and PLP-1. The central NBD and patatin-like phospholipase activity of PLP-1 are essential for allorecognition and cell death, while the TPR domain and the polymorphic SNARE domain of SEC-9 function in conferring allelic specificity. Our data indicate that fungal NLR-like proteins function similar to NLR immune receptors in plants and animals, showing that NLRs are major contributors to innate immunity in plants and animals and for allorecognition in fungi.

Hyphae are microscopic filaments that elongate and branch to create networks of interconnected tubes. Understanding how they work remains a formidable challenge in experimental mycology. Important advances in hyphal research in the 20th century came from electron microscopy, which revealed clusters of cytoplasmic vesicles in the cell apex, and biochemical studies that identified the cell wall materials that are assembled at the tip. Early genetic experiments on hyphae based on mutant analysis were disappointing and provided little information on the relationship between genotype and phenotype. Progress has come more recently, in the first decades of this century, by combining the techniques of molecular genetics with modern imaging methods. Live-cell imaging has allowed us to study the dynamics of cell components in strains of fungi engineered with plasmids encoding proteins fused to fluorescent probes. This technology has provided significant insights on the growth process and yet the fundamentals of hyphal growth remain elusive. • Research on hyphal growth has advanced through live-cell imaging • Tracking the movement of proteins attached to fluorescent reporters has become a particularly valuable experimental tool • Many fundamental questions about the growth of fungal hyphae remain unanswered [ABSTRACT FROM AUTHOR]

Heterokaryosis is a system in which genetically distinct nuclei coexist within the same cytoplasm. While heterokaryosis dominates the life cycle of many fungal species, the transcriptomic changes associated with the transition from homokaryosis to heterokaryosis is not well understood. Here, we analyse gene expression profiles of homokaryons and heterokaryons from three phylogenetically and reproductively isolated lineages of the filamentous ascomycete Neurospora tetrasperma. We show that heterokaryons are transcriptionally distinct from homokaryons in the sexual stage of development, but not in the vegetative stage, suggesting that the phenotypic switch to fertility in heterokaryons is associated with major changes in gene expression. Heterokaryon expression is predominantly defined by additive effects of its two nuclear components. Furthermore, allele-specific expression analysis of heterokaryons with varying nuclear ratios show patterns of expression ratios strongly dependent on nuclear ratios in the vegetative stage. By contrast, in the sexual stage, strong deviations of expression ratios indicate a co-regulation of nuclear gene expression in all three lineages. Taken together, our results show two levels of expression control: additive effects suggest a nuclear level of expression, whereas co-regulation of gene expression indicate a heterokaryon level of control. [ABSTRACT FROM AUTHOR]

Timing by the circadian clock of Neurospora is associated with hyperphosphorylation of frequency (FRQ), which depends on anchoring casein kinase 1a (CK1a) to FRQ. It is not known how CK1a is anchored so that approximately 100 sites in FRQ can be targeted. Here, we identified two regions in CK1a, p1 and p2, that are required for anchoring to FRQ. Mutation of p1 or p2 impairs progressive hyperphosphorylation of FRQ. A p1‐mutated strain is viable but its circadian clock is non‐functional, whereas a p2‐mutated strain is non‐viable. Our data suggest that p1 and potentially also p2 in CK1a provide an interface for interaction with FRQ. Anchoring via p1‐p2 leaves the active site of CK1a accessible for phosphorylation of FRQ at multiple sites. [ABSTRACT FROM AUTHOR]

Tomato (Lycopersicon esculentum L.) is one of the most important vegetables, used as condiments, salad and cooked with various recipes. It is a good source of vitamin C, A, calcium, iron etc. However, per acre yield in Pakistan is quite lower as compared to other countries of the world due to various factors, including diseases. Tomato crop suffers by approximately 200 diseases worldwide, among them, Fusarium wilt of tomato is highly destructive fungal disease and has caused losses up to 49.5% in Pakistan. Early strategies to manage this devastating disease include the use of cultural, physical, and chemical control are suggested, but none of these provided positive impact except cultural methods. Keeping in view the importance and losses caused by Fusarium wilt of tomato the studies on its management with fungal bioagents was conducted. For this. different bioagents were tested in lab and fields against Fusarium oxysporum f.sp. lycopersici. The highest inhibition 89.63% was noted by Trichoderma harzianum followed by Neurospora sp. 87.40% in the poisoned food method. In pot experiments, the T. harzianum was found as highly successful then Neurospora sp., Chaetomium subaffine and Arthrinium sp. providing minimum disease incidence and lowest mortality percent at higher and medium concentrations. The highest plant biomass and lowest root infection percent were noted in T. harzianum followed by Neurospora sp., C. subaffine and Arthrinium sp. at medium and lower doses. The lowest response was recorded by Nigrospora sphaerica and Dermateaceae sp. In in-vivo trials, the highest response was observed in the treatment of T. harzianum followed by Neurospora sp., Arthrinium sp., N. sphaerica, respectively. The highest fruit yield was recorded by T. harzianum 6.66 (kg) and Neurospora sp. 5.66 (kg). Interestingly, Neurospora sp., Arthrinium sp., N. sphaerica, and Dermateaceae sp. have been first time recognized in the current study as potential bioagents against fusarium wilt of tomato. Based on the findings, it is suggested that T. harzianum and Neurospora sp., may be used as potential bioagents for ecofriendly management of tomato wilt disease. [ABSTRACT FROM AUTHOR]

The study is aimed at the molecular identification of ravine soil fungal isolates and their volatile organic compounds (VOCs) profiling. Chambal ravines of Morena, located at latitude 26°5'N and longitude 78°0' E at an elevation of 177 meters. Ravine soil is marked for depleted nutrients. The isolates were identified by macroscopic and microscopic examinations followed by molecular identification the extracted fungal DNA was amplified for specific internal transcribed spacer primer (ITS1/ITS4). The products were sequenced and deposited in GenBank (NCBI), sequence similarity was checked and a phylogram was constructed. The isolates were identified and named Porostereum sp. HGBS16 and Neurospora sp. PAMS29. The VOCs/bioactive molecules were allowed to produce under static submerged fermentation. VOCs/bioactive molecules extracted with polar solvent and characterized by GCMS analysis. Besides playing an active role in communication, the obtained VOCs have other useful attributes of industrial and other beneficial uses. The prevailing compounds produced by Neurospora sp. PAMS29 is octasiloxane (50.32%) followed by the production of octadecane (42.67%) and cyclopentasiloxane (7.01%) whereas Porostereum sp. HGB16 displayed bicyclo (2.2.1) heptane-2-one (86.09%), followed by dodecane (6.09%) and tetradecane (4.05%). The VOC octadecane is reported as a pheromone, a chemical messenger which is useful for mating in fungi. The Presence of octadecane confirms that Neurospora sp. PAMS29 used Pheromones as the mating messenger. Both fungal extracts showed the presence of vitamin C under screening test and exhibited good DPPH free radical scavenging activity with 76.74±7.81 inhibition by Porostereum sp. HGB16 whereas Neurospora sp. PAMS29 showed 82.1±6.47 percent inhibition activity. Results showed that the VOCs produced by fungal isolates have the potential for industrial uses and can be used in body care products in place of synthetic polysiloxanes, though the D5 is already reported to be used in cosmetics. This study introduces new fungal strains and their VOCs to the microbial research domain. Simultaneously the isolates are producing vitamin C and also exhibited the DPPH free radical scavenging activities. Both isolates are aromatic therefore it can be used in the perfume industry. Concluding, this is the first attempt at molecular identification of ravine soil fungal isolates and exploration of their VOCs. These results supported that VOCs are not waste products, they are very useful products at a certain level. [ABSTRACT FROM AUTHOR]

Francis Haxo has been known to us as a thoughtful, patient, and dedicated scientist of the highest order. As a genuine scholar, he meticulously mulled over ideas for years before publishing his research. One of us (GG) knew him through three other friends: Barbara B. Prézelin, 1948-2021; David (Dave) C. Fork, 1929-2020; Beatrice (Beazy) M. Sweeney, 1914-1989; additionally, Anitra Thorhaug (AT) knew him as she was the last student of Larry Blinks, with whom Haxo had worked with. Francis Haxo was very generous to his students, but he took a long time to finalize and submit their papers--to ensure that all was well. We provide here a glimpse of his research after a brief note on his personal life--remembering him more than a decade after his death. He was an unsung hero, and he deserves to be remembered by algal, marine, and plant biologists throughout the world. A thorough and detailed memorial to Francis Haxo and his research, will soon be published by Anitra Thorhaug, Graeme Berlyn, and Synnøve Liaaen-Jensen (2022). [ABSTRACT FROM AUTHOR]

Sexual reproduction in fungi allows genetic recombination and increases genetic diversity, allowing adaptation and survival. The velvet complex is a fungal-specific protein assembly that regulates development, pathogenesis, and secondary metabolism in response to environmental cues, such as light. In Neurospora crassa , this complex comprises VE-1, VE-2, and LAE-1. Deletion of ve-1 or ve-2 , but not lae-1 , leads to increased conidiation (asexual spore formation) and reduced sexual development. Mutants lacking ve-1 and/or ve-2 are female sterile and male fertile, indicating that a VE-1/VE-2 complex regulates the development of female structures. During sexual development, we observed differential regulation of 2,117 genes in dark and 4,364 genes in light between the wild type and the ∆ ve-1 strain. The pheromone response and cell wall integrity pathways were downregulated in the ∆ ve-1 mutant, especially in light. Additionally, we found reduced levels of both total and phosphorylated MAK-1 and MAK-2 kinases. In vitro experiments demonstrated the binding of VE-1 and VE-2 to the promoters of mak-1 and mak-2 , suggesting a direct regulatory role of VE-1/VE-2 in the transcriptional control of MAPK genes to regulate sexual development. Deletion of the photosensor gene white-collar 1 prevented the light-dependent inhibition of sexual development in the ∆ ve-1 mutant by increasing transcription of the pheromone response and cell wall integrity pathway genes to the levels in the dark. Our results support the proposal that the regulation of the MAP kinase pathways by the VE-1/VE-2 complex is a key element in transcriptional regulation that occurs during sexual development., Importance: Sexual reproduction generates new gene combinations and novel phenotypic traits and facilitates evolution. Induction of sexual development in fungi is often regulated by environmental conditions, such as the presence of light and nutrients. The velvet protein complex coordinates internal cues and environmental signals to regulate development. We have found that VE-1, a component of the velvet complex, regulates transcription during sexual development in the fungus Neurospora crassa . VE-1 regulates the transcription of many genes, including those involved in mitogen-activated protein kinase (MAPK) signaling pathways that are essential in the regulation of sexual development, and regulates the activity of the MAPK pathway. Our findings provide valuable insights into how fungi respond to environmental signals and integrate them into their reproductive processes.