Trematode Diplostomum pseudospathaceum inducing differential immune gene expression in sexual and gynogenetic gibel carp (Carassius gibelio): parasites facilitating the coexistence of two reproductive forms of the invasive species.

Introduction: Parasite-mediated selection is considered one of the potential mechanisms contributing to the coexistence of asexual-sexual complexes. Gibel carp (Carassius gibelio), an invasive fish species in Europe, often forms populations composed of gynogenetic and sexual specimens. Methods: The experimental infection was induced in gynogenetic and sexual gibel carp using eye-fluke Diplostomum pseudospathaceum (Trematoda), and the transcriptome profile of the spleen as a major immune organ in fish was analyzed to reveal the differentially expressed immunity-associated genes related to D. pseudospathaceum infection differing between gynogenetic and sexual gibel carp. Results: High parasite infection was found in gynogenetic fish when compared to genetically diverse sexuals. Although metacercariae of D. pseudospathaceum are situated in an immune-privileged organ, our results show that eye trematodes may induce a host immune response. We found differential gene expression induced by eye-fluke infection, with various impacts on gynogenetic and sexual hosts, documenting for the majority of DEGs upregulation in sexuals, and downregulation in asexuals. Differences in gene regulation between gynogenetic and sexual gibel carp were evidenced in many immunity-associated genes. GO analyses revealed the importance of genes assigned to the GO terms: immune function, the Notch signaling pathway, MAP kinase tyrosine/threonine/phosphatase activity, and chemokine receptor activity. KEGG analyses revealed the importance of the genes involved in 12 immunity-associated pathways - specifically, FoxO signaling, adipocytokine signaling, TGF-beta signaling, apoptosis, Notch signaling, C-type lectin receptor signaling, efferocytosis, intestinal immune network for IgA production, insulin signaling, virion - human immunodeficiency virus, Toll-like receptor signaling, and phosphatidylinositol signaling system. Discussion: Our study indicates the limited potential of asexual fish to cope with higher parasite infection (likely a loss of capacity to induce an effective immune response) and highlights the important role of molecular mechanisms associated with immunity for the coexistence of gynogenetic and sexual gibel carp, potentially contributing to its invasiveness.

Ultrastructural evaluation of the oocytes and spermatozoa of the scleractinian coral Mussismilia harttii.

Global coverage of living coral has declined by half since 1950s. Reef-building species have been severely impacted in this climate crisis scenario, compromising the future of coral reefs. Despite their importance, there is a lack of knowledge regarding the reproductive biology of scleractinian corals. In the present study, we evaluated through electron microscopy approaches, the gametes of the endemic Southwestern Atlantic coral Mussismilia harttii. We observed spherical oocytes with microvilli throughout the outer membrane. Fine granular material dispersed in cytoplasm, lipid granules, numerous yolk bodies, and mitochondria were identified in the oocytes. In addition, small Symbiodinium-like cells were observed, suggesting a vertical transmission from parental coral to oocytes. The spherical-head sperm presents a 9.3 ± 2.1 µm flagellum. The nucleus is located centrally in the head, and the centrioles are positioned between the nuclear base and the flagellar insertion, which is connected to the axoneme. This axoneme has a microtubular arrangement (9+2). Vesicles, underlining the inner plasma membrane, presented the same electron-dense pattern as the Golgi complex, and mitochondria positioned surrounding the axoneme. The vesicles present in the sperm may have a role as an acrosome since the oocytes do not develop any cell specialization for fertilization.

How the seagrass Posidonia oceanica flowering will benefit from climate change.

This study aimed at identifying the importance of the thermal framework preceding Posidonia oceanica flowering induction (autumn before the flowering year) and anthesis (summer of the flowering year). In 53 locations of Sardinia (Italy), 35 vertical shoots were collected in 2001, 2020 and 2023 and analyzed through lepidochronology, detecting past flowering events from 1991 to 2022. Flowering probability was positively correlated with autumn SST range and MHWs, stressing the importance of the temperature in the year preceding the flowering. Summer SST mean and Marine Cold Spell duration (the latter emerged as a novel outcome) also positively influenced flowering. A negative association was highlighted with the summer SST range. As the occurrence of MHWs will increase, and the SST range will also increase in the autumn and decrease in the summer, P. oceanica might benefit through a higher flowering frequency, leading to a greater resilience to disturbances due to higher genetic variation.

The ecology of lichenicolous lichens: a case-study in Italy.

This paper, with Italy as a case-study, provides a general overview on the ecology of lichenicolous lichens, i.e. those which start their life-cycle on the thallus of other lichens. It aims at testing whether some ecological factors do exert a positive selective pressure on the lichenicolous lifestyle. The incidence of some biological traits (photobionts, growth-forms and reproductive strategies) in lichenicolous and non-lichenicolous lichens was compared, on a set of 3005 infrageneric taxa potentially occurring in Italy, 189 of which are lichenicolous. Lichenicolous lichens have a much higher incidence of coccoid (non-trentepohlioid) green algae, crustose growth-forms and sexual reproduction. A matrix of the 2762 species with phycobionts and some main ecological descriptors was subjected to ordination. Lichenicolous lichens occupy a well-defined portion of the ecological space, tending to grow on rocks in dry, well-lit habitats where a germinating spore is likely to have a short life-span, at all altitudes. This corroborates the hypothesis that at least some of them are not true "parasites", as they are often called, but gather the photobionts - which have already adapted to local ecological conditions - from their hosts, eventually developing an independent thallus.

Multiple paternity, fertilization success, and male quality: Mating system variation in the eelgrass, Zostera marina.

Genetic diversity can modulate a population's response to a changing environment and plays a critical role in its ecological function. While multiple processes act to maintain genetic diversity, sexual reproduction remains the primary driving force. Eelgrass (Zostera marina) is an important habitat-forming species found in temperate coastal ecosystems across the globe. Recent increases in sea surface temperatures have resulted in shifts to a mixed-annual life-history strategy (i.e., displaying characteristics of both annual and perennial meadows) at its southern edge-of-range. Given that mating systems are intimately linked to standing levels of genetic variation, understanding the scope of sexual reproduction can illuminate the processes that shape genetic diversity. To characterize edge-of-range eelgrass mating systems, developing seeds on flowering Z. marina shoots were genotyped from three meadows in Topsail, North Carolina. In all meadows, levels of multiple mating were high, with shoots pollinated by an average of eight sires (range: 3-16). The number of fertilized seeds (i.e., reproductive success) varied significantly across sires (range: 1-25) and was positively correlated with both individual heterozygosity and self-fertilization. Outcrossing rates were high (approx. 70%) and varied across spathes. No clones were detected, and kinship among sampled flowering shoots was low, supporting observed patterns of reproductive output. Given the role that genetic diversity plays in enhancing resistance to and resilience from ecological disturbance, disentangling the links between life history, sexual reproduction, and genetic variation will aid in informing the management and conservation of this key foundation species.

Advancing gender transformative intersectional science for health justice: An ecosocial analysis.

At a time when health-oriented institutions both globally and nationally are increasingly recognizing the need to support research, interventions and training that engage with analysis of how gendered social systems shape population health, independent of and in conjunction with sex-linked biology, it is essential that this work reject biological essentialism and instead embrace embodied integration. In this essay, guided by the ecosocial theory of disease distribution, I clarify connections and distinctions between biological versus social reproduction and inheritance, underscore the non-equivalence of the categories "sex" and "race," and offer a set of examples analyzing the production of gendered health inequities and who needs to do what to address them. The examples concern the worlds of work (sexual harassment; breastfeeding; sex work), ecologic environments (water access; fracking, sexually transmitted infections, & sexual violence); sexual reproduction and reproductive justice (gender stereotyping of reproductive biology; sterilization abuse and abortion bans); and (4) gender transformative initiatives (violence; health interventions). To advance gender transformative intersectional science for health justice, I offer recommendations regarding requirements for justifying data conceptualization, analysis and governance that can be implemented by institutions with the power to shape the funding, translation, and publication of science involving gender, sex-linked biology, and the people's health.

Reproduction-associated pathways in females of gibel carp (Carassius gibelio) shed light on the molecular mechanisms of the coexistence of asexual and sexual reproduction.

Gibel carp (Carassius gibelio) is a cyprinid fish that originated in eastern Eurasia and is considered as invasive in European freshwater ecosystems. The populations of gibel carp in Europe are mostly composed of asexually reproducing triploid females (i.e., reproducing by gynogenesis) and sexually reproducing diploid females and males. Although some cases of coexisting sexual and asexual reproductive forms are known in vertebrates, the molecular mechanisms maintaining such coexistence are still in question. Both reproduction modes are supposed to exhibit evolutionary and ecological advantages and disadvantages. To better understand the coexistence of these two reproduction strategies, we performed transcriptome profile analysis of gonad tissues (ovaries) and studied the differentially expressed reproduction-associated genes in sexual and asexual females. We used high-throughput RNA sequencing to generate transcriptomic profiles of gonadal tissues of triploid asexual females and males, diploid sexual males and females of gibel carp, as well as diploid individuals from two closely-related species, C. auratus and Cyprinus carpio. Using SNP clustering, we showed the close similarity of C. gibelio and C. auratus with a basal position of C. carpio to both Carassius species. Using transcriptome profile analyses, we showed that many genes and pathways are involved in both gynogenetic and sexual reproduction in C. gibelio; however, we also found that 1500 genes, including 100 genes involved in cell cycle control, meiosis, oogenesis, embryogenesis, fertilization, steroid hormone signaling, and biosynthesis were differently expressed in the ovaries of asexual and sexual females. We suggest that the overall downregulation of reproduction-associated pathways in asexual females, and their maintenance in sexual ones, allows the populations of C. gibelio to combine the evolutionary and ecological advantages of the two reproductive strategies. However, we showed that many sexual-reproduction-related genes are maintained and expressed in asexual females, suggesting that gynogenetic gibel carp retains the genetic toolkits for meiosis and sexual reproduction. These findings shed new light on the evolution of this asexual and sexual complex.

Deep imaging reveals dynamics and signaling in one-to-one pollen tube guidance.

In the pistil of flowering plants, each ovule usually associates with a single pollen tube for fertilization. This one-to-one pollen tube guidance, which contributes to polyspermy blocking and efficient seed production, is largely different from animal chemotaxis of many sperms to one egg. However, the functional mechanisms underlying the directional cues and polytubey blocks in the depths of the pistil remain unknown. Here, we develop a two-photon live imaging method to directly observe pollen tube guidance in the pistil of Arabidopsis thaliana, clarifying signaling and cellular behaviors in the one-to-one guidance. Ovules are suggested to emit multiple signals for pollen tubes, including an integument-dependent directional signal that reaches the inner surface of the septum and adhesion signals for emerged pollen tubes on the septum. Not only FERONIA in the septum but ovular gametophytic FERONIA and LORELEI, as well as FERONIA- and LORELEI-independent repulsion signal, are involved in polytubey blocks on the ovular funiculus. However, these funicular blocks are not strictly maintained in the first 45 min, explaining previous reports of polyspermy in flowering plants.

Developmental stage dependent effects of posterior and germline regeneration on sexual maturation in Platynereis dumerilii.

Regeneration, regrowing lost and injured body parts, is an ability that generally declines with age or developmental transitions (i.e. metamorphosis, sexual maturation). Regeneration is also an energetically costly process, and trade-offs occur between regeneration and other costly processes such as growth, or sexual reproduction. Here we investigate the interplay of regeneration, reproduction, and developmental stage in the segmented worm Platynereis dumerilii. P. dumerilii can regenerate its whole posterior body axis, along with its reproductive cells, thereby having to carry out the two costly processes (somatic and germ cell regeneration) after injury. We specifically examine how developmental stage affects the success of germ cell regeneration and sexual maturation in developmentally young versus developmentally old organisms. We hypothesized that developmentally younger individuals (i.e. with gametes in early mitotic stages) will have higher regeneration success than the individuals at developmentally older stages (i.e. with gametes undergoing meiosis and maturation). Surprisingly, older amputated worms grew faster and matured earlier than younger amputees. To analyze germ cell regeneration during and after posterior regeneration, we used Hybridization Chain Reaction for the germline marker vasa. We found that regenerated worms start repopulating new segments with germ cell clusters as early as 14 days post amputation. In addition, vasa expression is observed in a wide region of newly-regenerated segments, which appears different from expression patterns during normal growth or regeneration in worms before gonial cluster expansion.

Illuminating the Cryptococcus neoformans species complex: unveiling intracellular structures with fluorescent-protein-based markers.

Cryptococcus neoformans is a fungal pathogen of the top critical priority recognized by the World Health Organization. This clinically important fungus also serves as a eukaryotic model organism. A variety of resources have been generated to facilitate investigation of the C. neoformans species complex, including congenic pairs, well-annotated genomes, genetic editing tools, and gene deletion sets. Here, we generated a set of strains with all major organelles fluorescently marked. We tested short organelle-specific targeting sequences and successfully labeled the following organelles by fusing the targeting sequences with a fluorescence protein: the plasma membrane, the nucleus, the peroxisome, and the mitochondrion. We used native cryptococcal Golgi and late endosomal proteins fused with a fluorescent protein to label these two organelles. These fluorescence markers were verified via colocalization using organelle-specific dyes. All the constructs for the fluorescent protein tags were integrated in an intergenic safe haven region. These organelle-marked strains were examined for growth and various phenotypes. We demonstrated that these tagged strains could be employed to track cryptococcal interaction with the host in phagocytosis assays. These strains also allowed us to discover remarkable differences in the dynamics of proteins targeted to different organelles during sexual reproduction. Additionally, we revealed that "dormant" spores transcribed and synthesized their own proteins and trafficked the proteins to the appropriate subcellular compartments, demonstrating that spores are metabolically active. We anticipate that these newly generated fluorescent markers will greatly facilitate further investigation of cryptococcal biology and pathogenesis.

Functional analysis of the mating type genes in Verticillium dahliae.

BACKGROUND: Populations of the plant pathogenic fungus Verticillium dahliae display a complex and rich genetic diversity, yet the existence of sexual reproduction in the fungus remains contested. As pivotal genes, MAT genes play a crucial role in regulating cell differentiation, morphological development, and mating of compatible cells. However, the functions of the two mating type genes in V. dahliae, VdMAT1-1-1, and VdMAT1-2-1, remain poorly understood. RESULTS: In this study, we confirmed that the MAT loci in V. dahliae are highly conserved, including both VdMAT1-1-1 and VdMAT1-2-1 which share high collinearity. The conserved core transcription factor encoded by the two MAT loci may facilitate the regulation of pheromone precursor and pheromone receptor genes by directly binding to their promoter regions. Additionally, peptide activity assays demonstrated that the signal peptide of the pheromone VdPpg1 possessed secretory activity, while VdPpg2, lacked a predicted signal peptide. Chemotactic growth assays revealed that V. dahliae senses and grows towards the pheromones FO-a and FO-α of Fusarium oxysporum, as well as towards VdPpg2 of V. dahliae, but not in response to VdPpg1. The findings herein also revealed that VdMAT1-1-1 and VdMAT1-2-1 regulate vegetative growth, carbon source utilization, and resistance to stressors in V. dahliae, while negatively regulating virulence. CONCLUSIONS: These findings underscore the potential roles of VdMAT1-1-1 and VdMAT1-2-1 in sexual reproduction and confirm their involvement in various asexual processes of V. dahliae, offering novel insights into the functions of mating type genes in this species.

Discovery of seed germinating fungi (Mycetinis scorodonius) from Gastrodia elata Bl. f. glauca S. chow in Changbai Mountain and examination of their germination ability.

Multi-generational asexual reproduction of Gastrodia elata Bl. will cause seedling species degeneration. Sexual reproduction of Gastrodia elata Bl. seed is an effective method to solve the problem of degeneration. The development of Gastrodia elata Bl. seeds cannot be separated from the germination fungus. However, there are few strains of germination fungus in production, and there is also the problem of species degradation in application for many years. It is very important for the sexual reproduction of Gastrodia elata Bl. to isolate more new strains of excellent germination fungus from the origin. This study used the Gastrodia elata Bl. f. glauca S. chow seeds germination vegetative propagation corms capture method to isolate its symbiotic germination fungus, and comprehensively identified the species of germination fungus by colony morphology, ITS, sporocarps regeneration and germination function, and compared the growth characteristics and germination ability with other germination fungus (Mycena purpureofusca, Mycena dendrobii and Mycena osmundicola). The germination fungus was isolated from the vegetative propagation corms of Gastrodia elata Bl. f. glauca S. chow seeds and named GYGL-1. After comprehensive identification, GYGL-1 was Mycetinis scorodonius. Compared with other germination fungus, GYGL-1 has fast germination speed, vigorous growth, and high germination ability for Gastrodia elata Bl. f. glauca S. chow seeds. Innovated the isolation method of Gastrodia elata Bl. seeds germination fungus, obtained the regenerated sporocarps of the germination fungus, and discovered that Mycetinis scorodonius has a new function of germinating Gastrodia elata Bl. f. glauca S. chow seeds, enriching the resource library of Gastrodia elata Bl. germination fungus.

Effects of MrwetA on Sexual Reproduction and Secondary Metabolism of Monascus ruber M7 Based on Transcriptome Analysis.

wetA, one of the conidiation center regulatory genes in many filamentous fungi, plays an important role in promoting asexual spores (conidia) maturation. Our recent research has found that knocking out or overexpressing MrwetA (a homolog of wetA) in Monascus ruber M7 does not affect the development of its asexual spores like other fungi, but both repress the development of its sexual spores (ascospores). However, the mechanism remains unclear. In this study, the function of MrwetA on sexual reproduction and secondary metabolism in M. ruber M7 was confirmed by a complementary experiment. Moreover, the regulatory roles of MrwetA in modulating the expression of genes involved in sexual reproduction, meiosis, and biosynthesis of Monascus pigment and citrinin were analyzed based on the transcriptional data. These results not only contribute to clarifying the regulation of the reproduction and secondary metabolism of Monascus spp., but also to enriching the regulation molecular mechanism of reproduction in filamentous fungi.

Advances in Understanding Fusarium graminearum: Genes Involved in the Regulation of Sexual Development, Pathogenesis, and Deoxynivalenol Biosynthesis.

The wheat head blight disease caused by Fusarium graminearum is a major concern for food security and the health of both humans and animals. As a pathogenic microorganism, F. graminearum produces virulence factors during infection to increase pathogenicity, including various macromolecular and small molecular compounds. Among these virulence factors, secreted proteins and deoxynivalenol (DON) are important weapons for the expansion and colonization of F. graminearum. Besides the presence of virulence factors, sexual reproduction is also crucial for the infection process of F. graminearum and is indispensable for the emergence and spread of wheat head blight. Over the last ten years, there have been notable breakthroughs in researching the virulence factors and sexual reproduction of F. graminearum. This review aims to analyze the research progress of sexual reproduction, secreted proteins, and DON of F. graminearum, emphasizing the regulation of sexual reproduction and DON synthesis. We also discuss the application of new gene engineering technologies in the prevention and control of wheat head blight.

Diversity of genome size and chromosome number in homothallic and heterothallic strains of the Closterium peracerosum-strigosum-littorale complex (Desmidiales, Zygnematophyceae, Streptophyta).

The evolutionary transitions of mating systems between outcrossing and self-fertilization are often suggested to associate with the cytological and genomic changes, but the empirical reports are limited in multicellular organisms. Here we used the unicellular zygnematophycean algae, the Closterium peracerosum-strigosum-littorale (C. psl.) complex, to address whether genomic properties such as genome sizes and chromosome numbers are associated with mating system transitions between homothallism (self-fertility) and heterothallism (self-sterility). Phylogenetic analysis revealed the polyphyly of homothallic strains, suggesting multiple transitions between homothallism and heterothallism in the C. psl. complex. Flow cytometry analysis identified a more than 2-fold genome size variation, ranging from 0.53 to 1.42 Gbp, which was positively correlated with chromosome number variation between strains. Although we did not find consistent trends in genome size change and mating system transitions, the mean chromosome sizes tend to be smaller in homothallic strains than in their relative heterothallic strains. This result suggests that homothallic strains possibly have more fragmented chromosomes, which is consistent with the argument that self-fertilizing populations may tolerate more chromosomal rearrangements.

Floral morph variation mediated by clonal growth and pollinator functional groups of Limonium otolepis in a heterostylous fragmented population.

Abstract. Heterostyly, a genetic style polymorphism, is linked to symmetric pollen transfer, vital for its maintenance. Clonal growth typically impacts sexual reproduction by influencing pollen transfer. However, the floral morph variation remains poorly understood under the combined effects of pollinators and clonal growth in heterostyly characterized by negative frequency-dependent selection and disassortative mating. We estimated morph ratios, ramets per genet and heterostylous syndrome and quantified legitimate pollen transfer via clonal growth, pollinators and reciprocal herkogamy between floral morphs in Limonium otolepis, a fragmented population composed of five subpopulations in the desert environment of northwestern China, with small flower and large floral morph variation. All subpopulations but one exhibited pollen-stigma morphology dimorphism. The compatibility between mating types with different pollen-stigma morphologies remained consistent regardless of reciprocal herkogamy. Biased ratios and ramets per genet of the two mating types with distinct pollen-stigma morphologies caused asymmetric pollen flow and varying fruit sets in all subpopulations. Short-tongued insects were the primary pollinators due to small flower sizes. However, pollen-feeding Syrphidae sp. triggered asymmetry in pollen flow between high and low sex organs, with short-styled morphs having lower stigma pollen depositions and greater variation. Clonal growth amplified this variation by reducing intermorph pollen transfer. All in all, pollinators and clonal growth jointly drive floral morph variation. H-morphs with the same stigma-anther position and self-incompatibility, which mitigate the disadvantages of sunken low sex organs with differing from the classical homostyly, might arise from long- and short-styled morphs through a 'relaxed selection'. This study is the first to uncover the occurrence of the H-morph and its associated influencing factors in a distylous plant featuring clonal growth, small flowers and a fragmented population.

A review on natural phenylbutanoid attractants: Occurrence, distribution, and role in nature, especially in relation to Dacini fruit fly behavior and pollination.

The natural occurrence, distribution (within a plant) and roles of four phenylbutanoid compounds (anisyl acetone, cue-lure, raspberry ketone and zingerone) are elucidated for the Asia-Pacific and Oceania regions. These phenylbutanoids may act individually or in combination to attract true fruit fly males belonging to a tribe Dacini of subfamily Dacinae (Diptera: Tepritidae). Of special interest are the mutualistic interactions between the Dacini fruit fly males and the tropical daciniphilous (attracting exclusively Dacini fruit flies) orchids - leading to cross pollination for the orchids and enchanced mating success for the flies. When offered to male flies, anisyl acetone and cue-lure are generally converted to raspberry ketone. Upon consumption, raspberry ketone and zingerone are individually sequestered in the male rectal (pheromonal) gland unchanged. Attracted male flies readily imbibe the phenylbutanoid(s) in the floral synomone to compliment the endogenously synthesized male sex pheromonal components - to enhance attraction of conspecific females during courtship as well as attract conspecific males to form 'leks'. The phenylbutanoid(s) may also act as an allomone to deter vertebrate predators, especially geckos, besides possessing antimicrobial and antioxidant activities. Cue-lure, raspberry ketone and zingerone are important attractants/lures used in pest surveillance and mass trapping under the integrated pest management (IPM) program against quarantine Dacini fruit fly pest species, particularly Bactrocera tryoni and Zeugodacus cucurbitae.

Zygospore development of Spirogyra (Charophyta) investigated by serial block-face scanning electron microscopy and 3D reconstructions.

Sexual reproduction of Zygnematophyceae by conjugation is a less investigated topic due to the difficulties of the induction of this process and zygospore ripening under laboratory conditions. For this study, we collected field sampled zygospores of Spirogyra mirabilis and three additional Spirogyra strains in Austria and Greece. Serial block-face scanning electron microscopy was performed on high pressure frozen and freeze substituted zygospores and 3D reconstructions were generated, allowing a comprehensive insight into the process of zygospore maturation, involving storage compound and organelle rearrangements. Chloroplasts are drastically changed, while young stages contain both parental chloroplasts, the male chloroplasts are aborted and reorganised as 'secondary vacuoles' which initially contain plastoglobules and remnants of thylakoid membranes. The originally large pyrenoids and the volume of starch granules is significantly reduced during maturation (young: 8 ± 5 µm³, mature: 0.2 ± 0.2 µm³). In contrast, lipid droplets (LDs) increase significantly in number upon zygospore maturation, while simultaneously getting smaller (young: 21 ± 18 µm³, mature: 0.1 ± 0.2 and 0.5 ± 0.9 µm³). Only in S. mirabilis the LD volume increases (34 ± 29 µm³), occupying ~50% of the zygospore volume. Mature zygospores contain barite crystals as confirmed by Raman spectroscopy with a size of 0.02 - 0.05 µm³. The initially thin zygospore cell wall (~0.5 µm endospore, ~0.8 µm exospore) increases in thickness and develops a distinct, electron dense mesospore, which has a reticulate appearance (~1.4 µm) in Spirogyra sp. from Greece. The exo- and endospore show cellulose microfibrils in a helicoidal pattern. In the denser endospore, pitch angles of the microfibril layers were calculated: ~18 ± 3° in S. mirabilis, ~20 ± 3° in Spirogyra sp. from Austria and ~38 ± 8° in Spirogyra sp. from Greece. Overall this study gives new insights into Spirogyra sp. zygospore development, crucial for survival during dry periods and dispersal of this genus.

Recombination and repeat-induced point mutation landscapes reveal trade-offs between the sexual and asexual cycles of Magnaporthe oryzae.

The fungal disease caused by Magnaporthe oryzae is one of the most devastating diseases that endanger many crops worldwide. Evidence shows that sexual reproduction can be advantageous for fungal diseases as hybridization facilitates host-jumping. However, the pervasive clonal lineages of M. oryzae observed in natural fields contradict this expectation. A better understanding of the roles of recombination and the fungi-specific repeat-induced point mutation (RIP) in shaping its evolutionary trajectory is essential to bridge this knowledge gap. Here we systematically investigate the RIP and recombination landscapes in M. oryzae using a whole genome sequencing data from 252 population samples and 92 cross progenies. Our data reveal that the RIP can robustly capture the population history of M. oryzae, and we provide accurate estimations of the recombination and RIP rates across different M. oryzae clades. Significantly, our results highlight a parent-of-origin bias in both recombination and RIP rates, tightly associating with their sexual potential and variations of effector proteins. This bias suggests a critical trade-off between generating novel allelic combinations in the sexual cycle to facilitate host-jumping and stimulating transposon-associated diversification of effectors in the asexual cycle to facilitate host coevolution. These findings provide unique insights into understanding the evolution of blast fungus.

Transcriptional chronology reveals conserved genes involved in pennate diatom sexual reproduction.

Sexual reproduction is a major driver of adaptation and speciation in eukaryotes. In diatoms, siliceous microalgae with a unique cell size reduction-restitution life cycle and among the world's most prolific primary producers, sex also acts as the main mechanism for cell size restoration through the formation of an expanding auxospore. However, the molecular regulators of the different stages of sexual reproduction and size restoration are poorly explored. Here, we combined RNA sequencing with the assembly of a 55 Mbp reference genome for Cylindrotheca closterium to identify patterns of gene expression during different stages of sexual reproduction. These were compared with a corresponding transcriptomic time series of Seminavis robusta to assess the degree of expression conservation. Integrative orthology analysis revealed 138 one-to-one orthologues that are upregulated during sex in both species, among which 56 genes consistently upregulated during cell pairing and gametogenesis, and 11 genes induced when auxospores are present. Several early, sex-specific transcription factors and B-type cyclins were also upregulated during sex in other pennate and centric diatoms, pointing towards a conserved core regulatory machinery for meiosis and gametogenesis across diatoms. Furthermore, we find molecular evidence that the pheromone-induced cell cycle arrest is short-lived in benthic diatoms, which may be linked to their active mode of mate finding through gliding. Finally, we exploit the temporal resolution of our comparative analysis to report the first marker genes for auxospore identity called AAE1-3 ("Auxospore-Associated Expression"). Altogether, we introduce a multi-species model of the transcriptional dynamics during size restoration in diatoms and highlight conserved gene expression dynamics during different stages of sexual reproduction.