蕨类植物的配子体和早期孢子体对微生物的依赖

… fern spores and gametophytes to germinate and function in a combination of stressful conditions, and our results suggest that fern gametophytes … new fern populations is dependent on …

The multicellular haploid generation of plants (gametophyte) is responsible for sperm and egg production. In the fern Ceratopteris richardii, gametophytes are free-living and may develop into either males or hermaphrodites. This developmental decision is not genetically programmed, but instead is environmentally determined. A pheromone released by hermaphrodites called antheridiogen induces individuals to develop as males. The presence of the bacterium Pseudomonas nitroreducens blocks male induction and results in more individuals developing as hermaphrodites. The bacterium also induces longer but fewer rhizoids to develop in both males and hermaphrodites.

New pathways in plants and microbes Plants and microbes have interacted through evolution in ways that shaped diversity and helped plants colonize land. Delaux and Schornack review how insights from a range of plant and algal genomes reveal sustained use through evolution of ancient gene modules as well as emergence of lineage-specific specializations. Mosses, liverworts, and hornworts have layered innovation onto existing pathways to build new microbial interactions. Such innovations may be transferrable to crop plants with an eye toward building a more sustainable agriculture. Science, this issue p. eaba6605 BACKGROUND Microbial interactions have shaped plant diversity in terrestrial ecosystems. By forming mutually beneficial symbioses, microbes helped plants colonize land more than 450 million years ago. In parallel, omnipresent pathogens led to the emergence of innovative defense strategies. The evolution of plant-microbe interactions encompasses ancient conserved gene modules, recurrent concepts, and the fast-paced emergence of lineage-specific innovations. Microbes form communities on the surface or inside plant tissues and organs, and most intimately, microbes live within single plant cells. Intracellular colonization is established and controlled in part by plant genes that underpin general cell processes and defense mechanisms. To benefit from microbes, plants also evolved genetic modules for symbiosis support. These modules have been maintained despite the risk of getting hijacked by pathogens. ADVANCES The hundreds of land plant and algal genomes that are now available enable genome-wide comparisons of gene families associated with plant immunity and symbiosis. Reconstruction of gene phylogenies and large-scale comparative phylogenomic approaches have revealed an ancient subset of genes coevolving with the widespread arbuscular mycorrhiza symbiosis, the most ancient plant intracellular symbiosis, and with other types of more recently evolved intracellular symbioses in vascular and nonvascular plants. Intercellular symbiotic interactions formed with cyanobacteria or ectomycorrhizal fungi seem to repeatedly evolve through convergent, but not necessarily genetically conserved, mechanisms. Phylogenetic analyses revealed occurrence of candidate disease-resistance genes in green algae, as well as orthologs of flowering plant genes involved in symbiosis signaling and sensing microbial patterns. Yet, more research is needed to understand their functional conservation. The extent to which conserved symbiosis genes also fulfill often opposing roles during pathogen-plant interactions is being explored through studies of pathogen infections in plants capable of supporting symbiotic relationships. The development of plant-microbe systems in genetically tractable species covering the diversity of land plant lineages—including angiosperms and bryophytes, such as the liverwort Marchantia polymorpha—makes it possible to test hypotheses that emerge from phylogenetic analyses, linking genetic and functional conservation across land plants. Studies in bryophytes illustrate the range of possibilities for pathogen management: ancient genes, such as membrane receptors that perceive fungus-derived chitin; pathways with bryophyte clade–specific components, such as phenylpropanoid-derived auronidin stress metabolites; and jasmonate-like hormonal signaling for immunity. OUTLOOK Only a few plant-microbe interactions have been studied in depth, and those in only a few land plant lineages. Future investigations of interactions occurring across the diversity of plants may unravel new types of symbiotic or pathogenic interactions. The occurrence of microbe-sensing genes in streptophyte algae, harboring the closest algal relative to land plants, suggest the existence of overlooked and potentially ancient symbiotic associations. Genetically tractable plant-microbe model systems in diverse streptophyte algae, hornworts, liverworts, ferns, and the so far unsampled diversity of seed plants will enable dissection of the spectrum of molecular mechanisms that regulate the breadth of interactions occurring in plants. The actual function of the symbiotic genes present in bryophyte genomes also remains to be determined. Furthermore, our understanding of plant-microbe interactions will be enriched by more often combining evolutionary concepts with mechanistic studies. More efforts are needed to decipher the molecular changes that have enabled the emergence of new interactions, signaling pathways, and enzymatic specificities to support symbiosis and to protect against pathogens. Microbes manipulate plant processes, and complementary microbial studies are key to gaining a complete picture of plant-microbe evolution. Knowing the rules of engagement between distantly related plants and their microbes then helps genetic transplantation approaches into crops and the orthogonal engineering of bioprocesses aimed at achieving quantitative resistance against pathogens, improving phosphate uptake, or establishing nitrogen-fixing associations for efficient use in sustainable agriculture. Ancient friends and recent enemies shape plant evolution. Some pathogens such as oomycetes are able to infect a wide range of extant plant lineages, including bryophytes (left), and plant pathogen interactions often evolve at a fast pace. By contrast, some symbiotic interactions that look exactly as they do today can be found in the most ancient land plant fossils, here depicted as an illustration of the Rhynie chert fossil plant Aglaophyton major (right). Still, both types of plant-microbe interactions feature evolutionarily ancient as well as rapidly evolving aspects. Extending plant-microbe studies across diverse groups of plant lineages has enriched our understanding of these processes and their evolution. During 450 million years of diversification on land, plants and microbes have evolved together. This is reflected in today’s continuum of associations, ranging from parasitism to mutualism. Through phylogenetics, cell biology, and reverse genetics extending beyond flowering plants into bryophytes, scientists have started to unravel the genetic basis and evolutionary trajectories of plant-microbe associations. Protection against pathogens and support of beneficial, symbiotic, microorganisms are sustained by a blend of conserved and clade-specific plant mechanisms evolving at different speeds. We propose that symbiosis consistently emerges from the co-option of protection mechanisms and general cell biology principles. Exploring and harnessing the diversity of molecular mechanisms used in nonflowering plant-microbe interactions may extend the possibilities for engineering symbiosis-competent and pathogen-resilient crops.

… Fertilization results in the formation of an embryo, initially dependent on the gametophyte for … If the laboratory and equipment are clean, few microbial contaminants grow, and any growth …

… Furthermore, based on lack of nutrient availability in local soils, formation of specialized structures in the gametophyte for harboring fungi, and dependence of the fern on fungal …

Fungal endophytes are critical members of the plant microbiome, but their community dynamics throughout an entire growing season are underexplored. Additionally, most fungal endophyte research has centred on seed‐reproducing hosts, while spore‐reproducing plants also host endophytes and may be colonized by unique community members. In order to examine annual fungal endophyte community dynamics in a spore‐reproducing host, we explored endophytes in a single population of ferns, Polystichum munitum, in the Pacific Northwest. Through metabarcoding, we characterized the community assembly and temporal turnover of foliar endophytes throughout a growing season. From these results, we selected endophytes with outsized representations in sequence data and performed in vitro competition assays. Finally, we inoculated sterile fern gametophytes with dominant fungi observed in the field and determined their effects on host performance. Sequencing demonstrated that ferns were colonized by a diverse community of fungal endophytes in newly emerged tissue, but diversity decreased throughout the season leading to the preponderance of a single fungus in later sampling months. This previously undescribed endophyte appears to abundantly colonize the host to the detriment of other microfungi. Competition assays on a variety of media types failed to demonstrate that the dominant fungus was competitive against other fungi isolated from the same hosts, and inoculation onto sterile fern gametophytes did not alter growth compared to sterile controls, suggesting its effects are not antagonistic. The presence of this endophyte in the fern population probably demonstrates a case of repeated colonization driving competitive exclusion of other fungal community members.

The morphology of a Glomus-like fungus-host interaction in chlorophyllous gametophytes and young apogamic sporophytes of Dryopteris muenchii A.R. Sm. was studied from ferns cultivated in laboratory, using soil as substrate. An aseptate fungus colonized the gametophytes tissue through the rhizoids, developing vesicles. The fungus penetrated the young sporophytes primary roots by developing appressoria. It spread forming inter- and intra-cellular hyphae through the epidermis and the outermost cortical cell layers, where it formed vesicles, hyphal coils-like and arbuscules. The fungus hyphae never colonized the gametophytesporophyte cellular junction. The fungal structures observed on D. muenchii during this study, are rather similar to those reported for the plant host-arbuscular mycorrhizal fungus (AMF) interaction, where the AMF described belonged to Phylum Glomeromycota. Therefore, this study is a contribution to the scarce knowledgement of the association between AMF and chlorophyllous gametophytes and young apogamic sporophytes of ferns.

… underlying this key interaction between plants and fungi. Here we … the fern sporophytes and a highly specific fungal partner … this eusporangiate fern and Glomeromycota fungus, the …

Fungal associations in gametophytes and young sporophytic roots of the fern Nephrolepis exaltata Information is limited on the presence of endophytic fungal associations in green gametophytes and young sporophytes of extant ferns. Nothing is known about their presence in Polypodiales, the largest order among extant ferns. We screened chlorophyllous gametophytes and young sporophytes of Nephrolepis exaltata (L.) Schott., (Lomariopsidaceae, Polypodiales) growing naturally on soil, brick and coir for the presence of fungal endophytes. Gametophytes and young sporophytes growing on different substrates were invariably colonized by septate endophytic fungi. Hyaline or brown, regularly septate, inter- or intracellular hyphae with moniliform cells or microsclerotia characterized septate endophytic fungi. However, only the roots of young sporophytes growing on soil and bricks harboured arbuscular mycorrhizal (AM) fungi. The AM morphology conformed to the intermediate type with intracellular hyphal coils, arbusculate coils and intercellular hyphae. No AM fungal spores could be retrieved from the soil on which gametophytes and young sporophytes were growing. The observations in this study support the idea that the septate fungal endophytes could confer an ecological advantage on colonized individuals, especially on nutrient deficient substrates.

Many plant species experience a prolonged subterranean phase during which they rely entirely on mycorrhizal fungi for carbon. While this mycoheterotrophic strategy spans liverworts, lycophytes, and ferns, most empirical research has centered on angiosperms. This study explores the fungal associations of Sceptridium (Ophioglossaceae), an early‐diverging fern with mycoheterotrophic gametophytes. We analyzed germination patterns and fungal associations in Sceptridium gametophytes, comparing them to the distribution and mycorrhizal partners of photosynthetic sporophytes. High‐throughput sequencing data reveal that mycoheterotrophic gametophytes consistently associate with a single Entrophospora fungus in the order Entrophosporales (Glomeromycotina), while photosynthetic sporophytes primarily partner with fungi from Glomeraceae (Glomerales, Glomeromycotina). Consequently, gametophytes exhibit spatial clustering without association with adult plants. This is the first documentation of an association between Entrophosporaceae (and the order Entrophosporales) and mycoheterotrophic plants. The drastic shifts in Sceptridium mycorrhizal communities across life stages likely reflect changing physiological needs during development. Further research is essential to determine whether the association with Entrophosporaceae is widespread among mycoheterotrophic species and to elucidate the functional and physiological mechanisms underlying these mycorrhizal shifts.

… Significant main effects and interaction effects were followed up with post hoc pairwise … flexuosa shares the same fungal associations as gametophytes and analyze the genetic …

… between a eusporangiate fern and fungi of the Glomeromycota. … by a fungus in supporting the heterotrophic juvenile life stage … interactions and suppression of the growth of O. vulgatum …

… of the protocorm, a juvenile sporophytic structure apparently … gametophytes of gleichenaceous ferns and the liverworts … Interactions between fungi and plants through the ages. Can. …

… Despite of the growing interest in fungal interaction, knowledge of … The sporophytes were carefully removed from the … This may have been due to sampling juvenile individuals, in …

… juvenile sporophytes tested (Fig. 2e,f; Table S4). Although there was little to no exchange of plant-fixed C for fungal-acquired nutrients in juvenile sporophytes, … in their interactions with …

… life cycle phases of the ferns Botrychium crenulatum and B. lanceolatum. We … sporophytes of B. crenulatum share specific 18S AM … of mycoheterotrophic plant–fungal interactions (mostly …

… The main objective of the present study was to investigate mycorrhizal associations of a fern that appeared abundantly on soil samples collected at the Agnes Mine, Mpumalanga …

… are similarly colonized by AM fungi, suggesting that mycorrhizal associations with AM fungi … mycorrhizal status of field-collected gametophytes of entire groups of leptosporangiate ferns. …

… To clarify the mycorrhizal association of photosynthetic gametophytes, field-… the mycorrhizal association of aboveground photosynthetic gametophytes, we collected wild gametophytes …

… preference of lycophytes and ferns with their mycorrhizal status in a phylogenetic context. … , that are 100 % associated with AMF as gametophytes and sporophytes, yet they are almost …

… Mucoromycotina colonize fern gametophytes, we subjected fungal associations with … Arbuscular mycorrhizal colonization was confirmed in both fern species using an AM-specific primer …

… in mycorrhizal ferns or fern allies. Moreover, no data are available on the metal distribution in gametophytes … for growth, its potential association with mycorrhizal fungi may be significant. …

… mycorrhizal support, have been able to sustain Botrychium populations through changing environments. We present a depiction of the fern … between belowground gametophytes may be …

… gametophytes of H. hypogeae and might form AM associations with the obligate mycorrhizal gametophytes … specific pattern of association that we have uncovered in lycopods and ferns. …

Mycorrhizal association is one of the earliest and diversely distributed symbiotic associations on the Earth. This association helped early terrestrial plants to colonize the land by improved supply of nutrients like phosphate, nitrogen and zinc. It also helped plants to tolerate unfavorable soil conditions with increased water retention capacity, resistance to drought and pathogens. In return, fungi benefitted with carbon as their food source from the plants. More than 80% of terrestrial plants including pteridophytes, gymnosperms and angiosperms are reported to form arbuscular mycorrhizal (AM) association. Plants with root systems appeared on land during the Devonian period and many of them like pteridophytes still exist today. Various molecular and fossil studies confirm that the plants belonging to Ordovician-Devonian are associated with fungi, which are very similar to genus Glomus. AM association is very common in pteridophytes and the growth of its sporophyte and gametophyte is directly affected in the presence of AM association. Pteridophytes as early land plants with root systems have a very significant place in the plant kingdom. They have evolved and adapted to fill various habitats and facilitated early terrestrialization of other land plants by providing suitable niche with the help of AM fungi. In spite of pteridophytes being a very important plant group in the land system, very few reports are available on fungal-pteridophyte association. The present review is an effort to gather information about AM association in pteridophytes that might help in unraveling the evolution and significance of plant and fungi association.

… exaltata and stimulated growth … microorganisms, as are most soils (Lockwood, 1977; Ko and Ho, 1984). However, in the presence of light, the germination rates of spores of all three fern …

… There was no indication of contamination with fungi or bacteria. A few of the prothalli were … Nevertheless, the presence of the fungus stimulated growth and, since the stimulation was …

… to the effect of bacteria which grew in his cultures. Equisetum spores germinated readily in … these solutions give a stimulus to the transformation of the substances in the spore to starch. …

… study of the fungal endophytes and vascular anatomy in the rhizomes and gametophytes of … Much to our surprise, however, the same was also true for Tmesipteris growing on tree fern …

… plants and show the typical life cycle of most fern allies. In contrast to seed plants, both the … fungus. To verify this hypothesis, we investigated fungal endophytes of several gametophytes …

… Fern gametophytes may also be phyllous mycothalli of ferns. The only recent study associated with endophytic fungi and, in … gametophytes structure of the fungal endophyte in the …

… the gametophyte. The writer has recently had occasion to study the behavior of this endophyte in the gametophyte … The fungus consists of nonseptate, large, branched hyphm, which are …

Lygodium sp. is a climbing fern that occurs in open forests, settling frequently in areas with disturbed vegetation. In Argentina, Lygodium venustum inhabits in the protected area "Moconá" Provincial Park, in few and small populations. In-vitro cultivation of spores is a strategy for ex-situ conservation of species with reduced or threatened populations. Usually, fern spores need to be surface sterilized before sowing, to avoid the development of unwanted microorganisms. As part of our project focused on the conservation of native fern species in Argentina, the aim of this work was to evaluate a propagation protocol for L. venustum through in-vitro cultivation of spores, employing a standard procedure of disinfection, to investigate its effect on spore germination and the subsequent gametophyte as well as its response by the inoculation with a fungus. A batch of spores was previously treated with 10% (v/v) solution of NaOCl during 2 min and then sown in Dyer agar medium supplemented with 1% Nystatin (T1). The petri dishes were incubated in a growth chamber under white illumination (28μmol m-2 s-1) with a photoperiod of 12 hr and a temperature of 22±2°C. Another set of spores without previous disinfection was sown on Dyer agar medium and under the same conditions and used as a control (T0). Spore germination and gametophyte and sporophyte development were monitored through periodical observations under stereoscopic and light microscopes. As during cultures of non-disinfected spores a fungus developed in association with L. venustum gametophytes, its conidia were morphologically characterized as well as those obtained from the black spots present on the sporophyte leaves. A conidial suspension was applied to 20 days-old gametophytes obtained in axenic conditions to evaluate the appearance of any symptom. In both treatments (T1 and T0), spores germinated at 7 days after sowing. The pattern of spore germination followed the Anemia-type, unlike the Vittaria-type found by other researchers. Untreated spores showed a higher mean percentage of germination than those treated (86 and 72 % in 30 days, respectively). In T0 gametophytes grew in association with a fungus, whose conidia had the morphological characteristics of Pestalotiopsis maculans, as occurred with the conidia obtained from the black spots of L. venustum leaves. The association of P. maculans with L. venustum is reported here for the first time. The gametophytes developed in T0 and those inoculated with P. maculans became necrotic and died before producing gametangia, suggesting a pathogenic role of the fungus. The elevated percentage of spore germination registered in T0 could also indicate some effect of P. maculans or its metabolites in the promotion of spore germination. Gametophytes developed in T1 became bisexual or unisexual male, which points to the presence of some antheridiogen that induces the production of antheridia on smaller or slower-growing gametophytes. The sporophytes arose after 4 months of spore sown in T1, pointing out the methodology employed here suitable for the ex-situ conservation of L. venustum.

… endophytes in the gametophytes … endophytic fungus from fern roots was not invariably achieved, and it may well be that some of these failures were due to the presence of endophytes …

… , and form receptacles for an endophytic and purported symbiotic fungus (Fig. 1b; Britton & … to the presence of gametophytes and colonized the gametophytes without harm to the host. …

… , AM presence and available space for AM colonization in the roots decreased. Whether … commend the filmy ferns as an ideal study group for further studies on fern mycorrhiza, not …

… It is widely thought that symbiotic soil fungi facilitated the colonization of the terrestrial … gametophyte is supported by fungi until commencement of autotrophy, at which point the fern ‘…

Land plants can absorb soil microbes (bacterial, fungal and algal) into their cells and tissues. Plant endophytes enhance plant growth, stimulate elongation of root hairs, increase branching of roots, allow plants access to more nutrients, and stimulate oxidative stress tolerance. In the rhizophagy cycle, microbes are absorbed from soil directly into plant root cells where nutrients are extracted oxidatively, which provides nutrients to support plant growth. Early land plants lacked true roots, but possessed non-photosynthetic filaments (e.g., caulonemata, rhizoids) that may have cultivated diazotrophic bacteria within their cells as a source of nitrogen, just as bryophyte and pteridophyte rhizoids do today. Extant land plant lineages, such as bryophytes, pteridophytes, gymnosperms, and flowering plants, often produce epidermal structures (e.g., trichomes, papillae, paraphyllia, scales) on their roots, leaves, stems, or thalli; these often contain symbiotic nitrogen-fixing bacteria. Little is understood about how plants interact with soil and plant microbiomes. In this article we present novel endophytic phenomena in diverse lineages of land plants (liverworts, ferns, monocots, and eudicots) and explain how such symbiotic systems might have evolved over hundreds of millions of years. Due to these endophytic and symbiotic systems, land plants have the capability to obtain nutrients from the environment. Cultivation practices used in commercial agriculture can detract from the innate capabilities of plants to use microbes as a source of nutrients and might be harmful to plant health.

… plants (SVP; lycophytes and pteridophytes). Nearly nothing is … Core plant microbiota likely arose over 450 million years and … root plants with an important sporophyte stage, compared to …

… such axenic cultures is difficult as both gametophytes and … between the roots or gametophytes of ferns with the mycelium is … 3), and experiments have been conducted on inoculating …