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1. An introgressed gene causes meiotic drive in Neurospora sitophila

   https://doi.org/10.1073/pnas.2026605118  

   Svedberg, Jesper; Vogan, Aaron A.; Rhoades, Nicholas A.; Sarmarajeewa, Dilini; Jacobson, David J.; Lascoux, Martin; Hammond, Thomas M.; Johannesson, Hanna (April 2021, Proceedings of the National Academy of Sciences)

   null (Ed.)

   Meiotic drive elements cause their own preferential transmission following meiosis. In fungi, this phenomenon takes the shape of spore killing, and in the filamentous ascomycete Neurospora sitophila , the Sk-1 spore killer element is found in many natural populations. In this study, we identify the gene responsible for spore killing in Sk-1 by generating both long- and short-read genomic data and by using these data to perform a genome-wide association test. We name this gene Spk-1 . Through molecular dissection, we show that a single 405-nt-long open reading frame generates a product that both acts as a poison capable of killing sibling spores and as an antidote that rescues spores that produce it. By phylogenetic analysis, we demonstrate that the gene has likely been introgressed from the closely related species Neurospora hispaniola , and we identify three subclades of N. sitophila , one where Sk-1 is fixed, another where Sk-1 is absent, and a third where both killer and sensitive strain are found. Finally, we show that spore killing can be suppressed through an RNA interference-based genome defense pathway known as meiotic silencing by unpaired DNA. Spk-1 is not related to other known meiotic drive genes, and similar sequences are only found within Neurospora . These results shed light on the diversity of genes capable of causing meiotic drive, their origin and evolution, and their interaction with the host genome. 

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2. Uncertainty in coprophilous fungal spore concentration estimates

   https://doi.org/10.3389/fevo.2022.1086109  

   Perrotti, Angelina G.; Ramiadantsoa, Tanjona; O’Keefe, Jennifer; Nuñez Otaño, Noelia (December 2022, Frontiers in Ecology and Evolution)

   The abundance of coprophilous (dung-inhabiting) fungal spores (CFS) in sedimentary records is an increasingly popular proxy for past megaherbivore abundance that is used to study megaherbivore-vegetation interactions, timing of megaherbivore population declines and extinctions, and the introduction of domesticated herbivores. This method often relies on counting CFS alongside pollen and tracers of known concentration such as exotic pollen or synthetic microspherules. Prior work has encouraged reporting CFS abundances as accumulation rates (spores/unit 2 /year) or concentration (spores/unit 3 ) instead of percentages relative to the total pollen abundance, because CFS percentages can be sensitive to fluctuations in pollen influx. In this work, we quantify the uncertainty associated with estimating concentration values at different total counts and find that high uncertainty is associated with concentration estimates using low to moderate total counts ( n = 20 to 200) of individual fungal spore types and tracers. We also demonstrate the effect of varying tracer proportions, and find that larger tracer proportions result in narrower confidence intervals. Finally, the probability of encountering a CFS spore from a specific taxon occurring in moderate concentrations (1,000 spores/unit 2 ) dramatically decreases after a low tracer count (∼50). The uncertainties in concentration estimates caused by calculating tracer proportion are a likely cause of the high observed variance in many CFS time series, especially when CFS or tracer concentrations are low. Thus, we recommend future CFS studies increase counts and report the uncertainty surrounding concentration values. For some records, reporting spore data as presence/absence rather than concentrations or counts is preferable, such as when performing high counts is not feasible. 

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3. Sporogenesis in Physcomitrium patens: Intergenerational collaboration and the development of the spore wall and aperture

   https://doi.org/10.3389/fcell.2023.1165293  

   Renzaglia, Karen S.; Ashton, Neil W.; Suh, Dae-Yeon (April 2023, Frontiers in Cell and Developmental Biology)

   Although the evolution of spores was critical to the diversification of plants on land, sporogenesis is incompletely characterized for model plants such as Physcomitrium patens . In this study, the complete process of P. patens sporogenesis is detailed from capsule expansion to mature spore formation, with emphasis on the construction of the complex spore wall and proximal aperture. Both diploid (sporophytic) and haploid (spores) cells contribute to the development and maturation of spores. During capsule expansion, the diploid cells of the capsule, including spore mother cells (SMCs), inner capsule wall layer (spore sac), and columella, contribute a locular fibrillar matrix that contains the machinery and nutrients for spore ontogeny. Nascent spores are enclosed in a second matrix that is surrounded by a thin SMC wall and suspended in the locular material. As they expand and separate, a band of exine is produced external to a thin foundation layer of tripartite lamellae. Dense globules assemble evenly throughout the locule, and these are incorporated progressively onto the spore surface to form the perine external to the exine. On the distal spore surface, the intine forms internally, while the spiny perine ornamentation is assembled. The exine is at least partially extrasporal in origin, while the perine is derived exclusively from outside the spore. Across the proximal surface of the polar spores, an aperture begins formation at the onset of spore development and consists of an expanded intine, an annulus, and a central pad with radiating fibers. This complex aperture is elastic and enables the proximal spore surface to cycle between being compressed (concave) and expanded (rounded). In addition to providing a site for water intake and germination, the elastic aperture is likely involved in desiccation tolerance. Based on the current phylogenies, the ancestral plant spore contained an aperture, exine, intine, and perine. The reductive evolution of liverwort and hornwort spores entailed the loss of perine in both groups and the aperture in liverworts. This research serves as the foundation for comparisons with other plant groups and for future studies of the developmental genetics and evolution of spores across plants. 

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4. Fungal Spore Seasons Advanced Across the US Over Two Decades of Climate Change

   https://doi.org/10.1029/2024GH001323  

   Wu, Ruoyu; Song, Yiluan; Head, Jennifer_R; Katz, Daniel_S_W; Peay, Kabir_G; Shedden, Kerby; Zhu, Kai (June 2025, GeoHealth)

   Abstract Phenological shifts due to climate change have been extensively studied in plants and animals. Yet, the responses of fungal spores—organisms important to ecosystems and major airborne allergens—remain understudied. This knowledge gap limits our understanding of their ecological and public health implications. To address this, we analyzed a long‐term (2003–2022), large‐scale (the continental US) data set of airborne fungal spores collected by the US National Allergy Bureau. We first pre‐processed the spore data by gap‐filling and smoothing. Afterward, we extracted 10 metrics describing the phenology (e.g., start and end of season) and intensity (e.g., peak concentration and integral) of fungal spore seasons. These metrics were derived using two complementary but not mutually exclusive approaches—ecological and public health approaches, defined as percentiles of total spore concentration and allergenic thresholds of spore concentration, respectively. Using linear mixed‐effects models, we quantified annual shifts in these metrics across the continental US. We revealed a significant advancement in the onset of the spore seasons defined in both ecological (11 days, 95% confidence interval: 0.4–23 days) and public health (22 days, 6–38 days) approaches over two decades. Meanwhile, total spore concentrations in an annual cycle and in a spore allergy season tended to decrease over time. The earlier start of the spore season was significantly correlated with climatic variables, such as warmer temperatures and altered precipitations. Overall, our findings suggest possible climate‐driven advanced fungal spore seasons, highlighting the importance of climate change mitigation and adaptation in public health decision‐making. 

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5. Comparative transcriptional analysis reveals gene expression changes in spore germination of opportunistic pathogenic fungi

   https://doi.org/10.1101/2025.02.03.636182  

   Kim, Da-Woon; Ebert, Malaika K; Moonjely, Soumya; Wang, Zheng; Yarden, Oded; Townsend, Jeffrey P; Trail, Frances (February 2025, bioRxiv)

   In opportunistic human pathogenic fungi, changes in gene expression play a crucial role in the progression of growth stages from early spore germination through host infection. Comparative transcriptomics between diverse fungal pathogens and non-pathogens provided insights into regulatory mechanisms behind the initiation of infectious processes. We examined the gene expression patterns of 3,845 single-copy orthologous genes (SCOGs) across five phylogenetically distinct species, including the opportunistic human pathogens Fusarium oxysporum, Aspergillus fumigatus, and A. nidulans, and nonpathogenic species Neurospora crassa and Trichoderma asperelloides, at four sequential stages of spore germination. Ancestral status of gene expression was inferred for nodes along the phylogeny. By comparing expression patterns of the SCOGs with their most recent common ancestor (MRCA), we identified genes that exhibit divergent levels of expression during spore germination when comparing fungal pathogens to non-pathogens. We focused on genes related to the MAPK pathway, nitrogen metabolism, asexual development, G-protein signaling, and conidial-wall integrity. Notably, orthologs of the transcription activator abaA, a known central regulator of conidiation, exhibited significant divergence in gene expression in F. oxysporum. This dramatic expression change in abaA was accompanied by structural modifications of phialides in F. oxysporum, and revealed how these changes impact development of offspring, formation of aerial hyphae, spore production, and pathogenicity. Our research provides insights into ecological adaptations observed during the divergence of these species, specifically highlighting how divergence in gene expression during spore germination contributes to their ability to thrive in distinct environments. 

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