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Effector secretion is crucial for root endophytes to establish and protect their ecological niche. We used time-resolved transcriptomics to monitor effector gene expression dynamics in two closely related Sebacinales, Serendipita indica and Serendipita vermifera, during symbiosis with three plant species, competition with the phytopathogenic fungus Bipolaris sorokiniana, and cooperation with root-associated bacteria. We observed increased effector gene expression in response to biotic interactions, particularly with plants, indicating their importance in host colonization. Some effectors responded to both plants and microbes, suggesting dual roles in intermicrobial competition and plant-microbe interactions. A subset of putative antimicrobial effectors, including a GH18-CBM5 chitinase, was induced exclusively by microbes. Functional analyses of this chitinase revealed its antimicrobial and plant-protective properties. We conclude that dynamic effector gene expression underpins the ability of Sebacinales to thrive in diverse ecological niches with a single fungal chitinase contributing substantially to niche defense.

Core Ericaceae produce delicate hair roots with inflated rhizodermal cells that host plethora of fungal symbionts. These poorly known mycobionts include various endophytes, parasites, saprobes, and the ericoid mycorrhizal (ErM) fungi (ErMF) that form the ErM symbiosis crucial for the fitness of their hosts. Using microscopy and high-throughput sequencing, we investigated their structural and molecular diversity in 14 different host × site combinations in Northern Bohemia (Central Europe) and Argentine Patagonia (South America). While we found typical ericoid mycorrhiza in all combinations, we did not detect ectomycorrhiza and arbuscular mycorrhiza. Superficial mantles of various thickness formed by non-clamped hyphae were observed in all combinations except Calluna vulgaris from N. Bohemia. Some samples contained frequent intercellular hyphae while others possessed previously unreported intracellular haustoria-like structures linked with intracellular hyphal coils. The 711 detected fungal OTU were dominated by Ascomycota (563) and Basidiomycota (119), followed by four other phyla. Ascomycetes comprised Helotiales (255), Pleosporales (53), Chaetothyriales (42), and other 19 orders, while basidiomycetes Sebacinales (42), Agaricales (28), Auriculariales (7), and other 14 orders. While many dominant OTU from both hemispheres lacked close relatives in reference databases, many were very similar to identical to unnamed sequences from around the world. On the other hand, several significant ericaceous mycobionts were absent in our dataset, incl. Cairneyella, Gamarada, Kurtia, Lachnum, and Leohumicola. Most of the detected OTU could not be reliably linked to a particular trophic mode, and only two could be reliably assigned to the archetypal ErMF Hyaloscypha hepaticicola. Probable ErMF comprised Hyaloscypha variabilis and Oidiodendron maius, both detected only in N. Bohemia. Possible ErMF comprised sebacinoid fungi and several unnamed members of Hyaloscypha s. str. While H. hepaticicola was dominant only in C. vulgaris, this model ErM host lacked O. maius and sebacinoid mycobionts. Hyaloscypha hepaticicola was absent in two and very rare in six combinations from Patagonia. Nine OTU represented dark septate endophytes from the Phialocephala fortinii s. lat.–Acephala applanata species complex, including the most abundant OTU (the only detected in all combinations). Statistical analyses revealed marked differences between N. Bohemia and Patagonia, but also within Patagonia, due to the unique community detected in a Valdivian temperate rainforest. Our results show that the ericaceous hair roots may host diverse mycobionts with mostly unknown functions and indicate that many novel ErMF lineages await discovery. Transhemispheric differences (thousands of km) in their communities may be evenly matched by local differences (scales of km, m, and less). [ABSTRACT FROM AUTHOR]

Bistorta vivipara is a widespread herbaceous perennial plant with a discontinuous pattern of distribution in arctic, alpine, subalpine and boreal habitats across the northern Hemisphere. Studies of the fungi associated with the roots of B. vivipara have mainly been conducted in arctic and alpine ecosystems. This study examined the fungal diversity and specificity from root tips of B. vivipara in two local mountain ecosystems as well as on a global scale. Sequences were generated by Sanger sequencing of the internal transcribed spacer (ITS) region followed by an analysis of accurately annotated nuclear segments including ITS1-5.8S-ITS2 sequences available from public databases. In total, 181 different UNITE species hypotheses (SHs) were detected to be fungi associated with B. vivipara, 73 of which occurred in the Bavarian Alps and nine in the Swabian Alps-with one SH shared among both mountains. In both sites as well as in additional public data, individuals of B. vivipara were found to contain phylogenetically diverse fungi, with the Basidiomycota, represented by the Thelephorales and Sebacinales, being the most dominant. A comparative analysis of the diversity of the Sebacinales associated with B. vivipara and other co-occurring plant genera showed that the highest number of sebacinoid SHs were associated with Quercus and Pinus, followed by Bistorta. A comparison of B. vivipara with plant families such as Ericaceae, Fagaceae, Orchidaceae, and Pinaceae showed a clear trend: Only a few species were specific to B. vivipara and a large number of SHs were shared with other co-occurring non-B. vivipara plant species. In Sebacinales, the majority of SHs associated with B. vivipara belonged to the ectomycorrhiza (ECM)-forming Sebacinaceae, with fewer SHs belonging to the Serendipitaceae encompassing diverse ericoid-orchid-ECM-endophytic associations. The large proportion of non-hostspecific fungi able to form a symbiosis with other non-B. vivipara plants could suggest that the high fungal diversity in B. vivipara comes from an active recruitment of their associates from the co-occurring vegetation. The non-host-specificity suggests that this strategy may offer ecological advantages; specifically, linkages with generalist rather than specialist fungi. Proximity to co-occurring non-B. vivipara plants can maximise the fitness of B. vivipara, allowing more rapid and easy colonisation of the available habitats. [ABSTRACT FROM AUTHOR]

Bistorta vivipara is a widespread herbaceous perennial plant with a discontinuous pattern of distribution in arctic, alpine, subalpine and boreal habitats across the northern Hemisphere. Studies of the fungi associated with the roots of B. vivipara have mainly been conducted in arctic and alpine ecosystems. This study examined the fungal diversity and specificity from root tips of B. vivipara in two local mountain ecosystems as well as on a global scale. Sequences were generated by Sanger sequencing of the internal transcribed spacer (ITS) region followed by an analysis of accurately annotated nuclear segments including ITS1-5.8S-ITS2 sequences available from public databases. In total, 181 different UNITE species hypotheses (SHs) were detected to be fungi associated with B. vivipara, 73 of which occurred in the Bavarian Alps and nine in the Swabian Alps–with one SH shared among both mountains. In both sites as well as in additional public data, individuals of B. vivipara were found to contain phylogenetically diverse fungi, with the Basidiomycota, represented by the Thelephorales and Sebacinales, being the most dominant. A comparative analysis of the diversity of the Sebacinales associated with B. vivipara and other co-occurring plant genera showed that the highest number of sebacinoid SHs were associated with Quercus and Pinus, followed by Bistorta. A comparison of B. vivipara with plant families such as Ericaceae, Fagaceae, Orchidaceae, and Pinaceae showed a clear trend: Only a few species were specific to B. vivipara and a large number of SHs were shared with other co-occurring non-B. vivipara plant species. In Sebacinales, the majority of SHs associated with B. vivipara belonged to the ectomycorrhiza (ECM)-forming Sebacinaceae, with fewer SHs belonging to the Serendipitaceae encompassing diverse ericoid–orchid–ECM–endophytic associations. The large proportion of non-host-specific fungi able to form a symbiosis with other non-B. vivipara plants could suggest that the high fungal diversity in B. vivipara comes from an active recruitment of their associates from the co-occurring vegetation. The non-host-specificity suggests that this strategy may offer ecological advantages; specifically, linkages with generalist rather than specialist fungi. Proximity to co-occurring non-B. vivipara plants can maximise the fitness of B. vivipara, allowing more rapid and easy colonisation of the available habitats.

• A next-generation sequencing approach was used to catalogue the fungal diversity in rhizosphere soil of the critically endangered South African orchid Brachycorythis conica subsp. transvaalensis • Several unique fungal species were identified from the rhizosphere of the orchid that were not present in the non-rhizosphere soils • Mycorrhizal fungi from the orders Agaricales, Cantharellales and Sebacinales were identified in the orchid's rhizosphere • This study will contribute to the isolation of suitable mycorrhizal species required for in vitro symbiotic germination of this orchid The Albertina Sisulu orchid, Brachycorythis conica subsp. transvaalensis is a critically endangered terrestrial orchid with a single population remaining in the Gauteng Province of South Africa. For the conservation of this endemic orchid, several strategies are being implemented such as protection of habitat, identifying pollinators and in vitro propagation. For symbiotic germination, it is essential to identify the mycorrhizal associates of this orchid using non-destructive sampling. In this study, high-throughput sequencing was used to catalogue and compare the diversity of fungi associated with the mycorrhizosphere of this orchid and non-mycorrhizosphere soils collected from the same coordinates. Bioinformatics and statistical analyses of the data showed that, despite the substantial overlap in the community composition of fungi associated with these two soil types, several exclusive fungal species were identified from the mycorrhizosphere of the orchid. These included an assortment of potential orchid mycorrhizal species from the orders Agaricales, Cantharellales and Sebacinales. This study provides the first insight into the soil fungal diversity associated with the mycorrhizosphere of this critically endangered orchid. In the future, data from this study can be used for optimising conservation measures and isolation of suitable mycorrhizal species required for in vitro symbiotic germination of this orchid. [ABSTRACT FROM AUTHOR]

Mutualistic mycorrhiza in orchids: evidence from plant-fungus carbon and nitrogen transfers in the green-leaved terrestrial orchid Goodyera repens. I sikokianus i and albino mutants of so-called rhizoctonia-associated orchids, including I Goodyera velutina i (8.8 ± 0.9‰; Suetsugu I et al i ., 2019) and I Cypripedium i I debile i (9.8 ± 0.5‰), are similar to those of mycoheterotrophic orchids exploiting saprotrophic nonrhizoctonia fungi. Keywords: carbon dynamics; mixotrophy; mycorrhizas; partial mycoheterotrophy; radiocarbon dating; rhizoctonias; saprotrophic fungi; Sebacinales EN carbon dynamics mixotrophy mycorrhizas partial mycoheterotrophy radiocarbon dating rhizoctonias saprotrophic fungi Sebacinales 1670 1675 6 08/07/21 20210901 NES 210901 Controversy on the nutritional mode of rhizoctonia-associated orchids Mycorrhizas usually engage in mutualism, in which soil fungi contribute minerals to plants that in turn supply photosynthetically fixed carbon (C) to their fungal partners (Smith & Read, 2008). Although all orchids depend on symbiotic fungi for essential nutrients (including C) during their initial development (Dearnaley I et al i ., 2016), most orchid species exhibit some level of autotrophy at the adult stage. [Extracted from the article]

Serendipita is one of the main fungal genera that form mutualistic associations with species of orchids (Orchidaceae). Here, seven new Serendipita species associated with various Australian orchid genera are described. These Serendipita species were originally characterized by multilocus DNA sequence species delimitation analyses (three mtDNA and four nuclear genes) and confirmed as distinct with addition of further isolates and reanalysis of nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and nuc 28S rDNA (28S). Culture morphology and microscopic features are presented for each species, three of which are binucleate and four multinucleate. For the ITS region, the seven species have within-species sequence divergence between 1.07% and 4.31%, and all but one of the species pairs is separated by interspecific divergence of at least 4.35%. The newly described Serendipita species, S. australiana, S. communis, S. occidentalis, S. rarihospitum, S. secunda, S. talbotii, and S. warcupii, are shown to be separate species from S. vermifera on the basis of comparison against a sequence from the type. Isolates originally identified by Warcup as Sebacina "vermifera" from Caladenia orchids are revised and shown to belong to three of the species newly described here. Some non-Caladenia isolates identified by Warcup as S. "vermifera" are also shown to be non-conspecific with the type of S. vermifera. On the basis of ITS sequences, 346 isolates from 26 other studies, previously identified under provisional designations, are accommodated under the novel species. The species of Serendipta described here associate with the Australian orchid genera Caladenia, Cyanicula, Elythranthera, Ericksonella, Eriochilus, Glossodia, and Pheladenia. Most of the novel Serendipita species occur widely across Australia, often with widely distributed hosts, but one species, Serendipita rarihospitum, associates with narrowly distributed orchid species. [ABSTRACT FROM AUTHOR]

Plants that produce dust seeds can recruit fungi to meet their earliest requirements for carbon and other nutrients. This germination strategy, termed initial mycoheterotrophy, has been well investigated among the orchid family, but there are numerous other plant lineages that have independently evolved mycoheterotrophic germination strategies. One of these lineages is the tribe Pyroleae (Ericaceae). While the fungi associated with mature plants in Pyroleae have been fairly well documented, their mycobionts at the germination and seedling stages are largely unknown. Here, we use an in situ seed baiting experiment along with molecular fingerprinting techniques and phylogenetic tests to identify the fungi associated with seedlings of two Pyroleae species, Pyrola chlorantha and Orthilia secunda. Our results indicate that similar to adult plants, Pyroleae seedlings can associate with a suite of ectomycorrhizal fungi. Some seedlings harboured single mycobionts, while others may have been inhabited by multiple fungi. The dominant seedling mycobiont of both Pyroleae species was a fungus of unknown trophic status in the order Sebacinales. This taxon was also the only one shared among seedlings of both investigated Pyroleae species. We discuss these results juxtaposed to orchids and one additional Pyrola species in the context of ontogenetic shifts in fungal host specificity for mycoheterotrophic nutrition.

We studied mycorrhizal symbioses of Cephalanthera falcata (Orchidaceae) in a population that included giant individuals, some of which were over 50 cm in height and had more than 10 shoots, as well as in two nearby habitats without giant individuals. For C. falcata adults in the habitat with giant individuals, a fungal lineage in the ectomycorrhiza‐forming clade of Sebacinales was detected as the dominant mycobiont. Furthermore, higher 13C enrichment, which is an indicator of mycoheterotrophy, was found in these C. falcata individuals compared to those in the two nearby habitats. These results indicate that the growth of giant C. falcata individuals may be a result of the increased ability of Sebacinales fungi to transfer carbon to the orchids. Furthermore, we attempted to discern the effect of mycobiont taxa on seedling development in the three habitats. Contrary to our expectations, Sebacinales fungi were not found to significantly impact seedling growth as this orchid was predominantly colonized by Thelephoraceae fungi at the seedling stage. These results suggest that seedling growth is mostly enhanced by symbiosis with Thelephoraceae fungi in this orchid, and that the growth of giant individuals due to colonization by Sebacinales fungi may occur subsequently. [ABSTRACT FROM AUTHOR]

Quercus virginiana (Fagaceae), native to the southeastern United States, has recently been introduced to the Yangtze Delta (China) and is often planted in landscaping and in coastal shelter forests. Here, we performed pot inoculation assays to evaluate the effects of two types of basidiomycetous root fungal symbionts, across four orders, on the growth and nutrient absorption of Q.virginiana seedlings. The results indicated that two isolates showed plant growth-promoting activities 2 months after inoculation. In particular, the ectomycorrhizal Sistotrema sp. (Cantharellales) had a pronounced effect on root development and morphology. With regard to nutrient absorption, the total nitrogen content in aboveground tissues was improved in inoculated seedlings, although most differences were not significant. Meanwhile, the total phosphorus contents in seedlings were either positively or negatively affected, probably depending on the symbiont type. Interestingly, the total potassium content in stems and leaves was significantly enhanced in all treatment groups. In addition, indole-3-acetic acid and abscisic acid production were determined in Sistotrema sp. and Atractiella rhizophila (Pucciniomycotina) by high-performance liquid chromatography tandem mass spectrometry. Our findings suggest that both endophytic and ectomycorrhizal fungi have beneficial effects on Q.virginiana growth, and highlight the potential for the development of mycobiome-based seedling raising techniques. [ABSTRACT FROM AUTHOR]

In the last decade, there has been an increasing focus on the implementation of plant growth-promoting (PGP) organisms as a sustainable option to compensate for poor soil fertility conditions in developing countries. Trap systems were used in an effort to isolate PGP fungi from rhizospheric soil samples collected in the region around Kisangani in the Democratic Republic of Congo. With sudangrass as a host, a highly conducive environment was created for sebacinalean chlamydospore formation inside the plant roots resulting in a collection of 51 axenically cultured isolates of the elusive genus Piriformospora (recently transferred to the genus Serendipita). Based on morphological data, ISSR fingerprinting profiles and marker gene sequences, we propose that these isolates together with Piriformospora williamsii constitute a species complex designated Piriformospora (D Serendipita) 'williamsii.' A selection of isolates strongly promoted plant growth of in vitro inoculated Arabidopsis seedlings, which was evidenced by an increase in shoot fresh weight and a strong stimulation of lateral root formation. This isolate collection provides unprecedented opportunities for fundamental as well as translational research on the Serendipitaceae, a family of fungal endophytes in full expansion. [ABSTRACT FROM AUTHOR]

• Mycorrhizal fungi are essential for the survival of orchid seedlings under natural conditions. The distribution of these fungi in soil can constrain the establishment and resulting spatial arrangement of orchids at the local scale, but the actual extent of occurrence and spatial patterns of orchid mycorrhizal (OrM) fungi in soil remain largely unknown. • We addressed the fine-scale spatial distribution of OrM fungi in two orchid-rich Mediterranean grasslands by means of high-throughput sequencing of fungal ITS2 amplicons, obtained from soil samples collected either directly beneath or at a distance from adult Anacamptis morio and Ophrys sphegodes plants. • Like ectomycorrhizal and arbuscular mycobionts, OrM fungi (tulasnelloid, ceratobasidioid, sebacinoid and pezizoid fungi) exhibited significant horizontal spatial autocorrelation in soil. However, OrM fungal read numbers did not correlate with distance from adult orchid plants, and several of these fungi were extremely sporadic or undetected even in the soil samples containing the orchid roots. • Orchid mycorrhizal 'rhizoctonias' are commonly regarded as unspecialized saprotrophs. The sporadic occurrence of mycobionts of grassland orchids in host-rich stands questions the view of these mycorrhizal fungi as capable of sustained growth in soil. [ABSTRACT FROM AUTHOR]

Terrestrial orchids depend on orchid mycorrhizal fungi (OMF) as symbionts for their survival, growth and nutrition. The ability of OMF from endangered orchid species to compete for available resources with OMF from common species may affect the distribution, abundance and therefore conservation status of their orchid hosts. Eight symbiotically effective OMF from endangered and more common Caladenia species were tested for their ability to utilise complex insoluble and simple soluble carbon sources produced during litter degradation by growth with different carbon sources in liquid medium to measure the degree of OMF variation with host conservation status or taxonomy. On simple carbon sources, fungal growth was assessed by biomass. On insoluble substrates, ergosterol content was assessed using ultra-performance liquid chromatography (UPLC). The OMF grew on all natural materials and complex carbon sources, but produced the greatest biomass on xylan and starch and the least on bark and chitin. On simple carbon sources, the greatest OMF biomass was measured on most hexoses and disaccharides and the least on galactose and arabinose. Only some OMF used sucrose, the most common sugar in green plants, with possible implications for symbiosis. OMF from common orchids produced more ergosterol and biomass than those from endangered orchids in the Dilatata and Reticulata groups but not in the Patersonii and Finger orchids. This suggests that differences in carbon source utilisation may contribute to differences in the distribution of some orchids, if these differences are retained on site. [ABSTRACT FROM AUTHOR]

Soil salinization adversely affects plant growth and has become one of the major limiting factors for crop productivity worldwide. The conventional approach, breeding salt-tolerant plant cultivars, has often failed to efficiently alleviate the situation. In contrast, the use of a diverse array of microorganisms harbored by plants has attracted increasing attention because of the remarkable beneficial effects of microorganisms on plants. Multiple advanced ‘- omics ’ technologies have enabled us to gain insights into the structure and function of plant-associated microbes. In this review, we first focus on microbe-mediated plant salt tolerance, in particular on the physiological and molecular mechanisms underlying root–microbe symbiosis. Unfortunately, when introducing such microbes as single strains to soils, they are often ineffective in improving plant growth and stress tolerance, largely due to competition with native soil microbial communities and limited colonization efficiency. Rapid progress in rhizosphere microbiome research has revived the belief that plants may benefit more from association with interacting, diverse microbial communities (microbiome) than from individual members in a community. Understanding how a microbiome assembles in the continuous compartments (endosphere, rhizoplane, and rhizosphere) will assist in predicting a subset of core or minimal microbiome and thus facilitate synthetic re-construction of microbial communities and their functional complementarity and synergistic effects. These developments will open a new avenue for capitalizing on the cultivable microbiome to strengthen plant salt tolerance and thus to refine agricultural practices and production under saline conditions. [ABSTRACT FROM AUTHOR]

The Sebacinales are a monophyletic group of ubiquitous hymenomycetous mycobionts which form ericoid and orchid mycorrhizae, ecto- and ectendomycorrhizae, and nonspecific root endophytic associations with a wide spectrum of plants. However, due to the complete lack of fungal isolates derived from Ericaceae roots, the Sebacinales ericoid mycorrhizal (ErM) potential has not yet been tested experimentally. Here, we report for the first time isolation of a serendipitoid (formerly Sebacinales Group B) mycobiont from Ericaceae which survived in pure culture for several years. This allowed us to test its ability to form ericoid mycorrhizae with an Ericaceae host in vitro, to describe its development and colonization pattern in host roots over time, and to compare its performance with typical ErM fungi and other serendipitoids derived from non-Ericaceae hosts. Out of ten serendipitoid isolates tested, eight intracellularly colonized Vaccinium hair roots, but only the Ericaceae-derived isolate repeatedly formed typical ericoid mycorrhiza morphologically identical to ericoid mycorrhiza commonly found in naturally colonized Ericaceae, but yet different from ericoid mycorrhiza formed in vitro by the prominent ascomycetous ErM fungus Rhizoscyphus ericae. One Orchidaceae-derived isolate repeatedly formed abundant hyaline intracellular microsclerotia morphologically identical to those occasionally found in naturally colonized Ericaceae, and an isolate of Serendipita (= Piriformospora) indica produced abundant intracellular chlamydospores typical of this species. Our results confirm for the first time experimentally that some Sebacinales can form ericoid mycorrhiza, point to their broad endophytic potential in Ericaceae hosts, and suggest possible ericoid mycorrhizal specificity in Serendipitaceae. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Few previous studies have examined how mycobionts change during the evolution from autotrophy to mycoheterotrophy based on phylogenetic hypotheses. Neottia (Orchidaceae) comprises leafy species that are autotrophic and related leafless mycoheterotrophic species, and the phylogenetic relationships among them have been clarified. Accordingly, Neottia is a suitable taxon for investigating the question above. Here we clarified the diversity of mycobionts in Neottia plants and elucidated changes in the character of symbiotic associations during the evolution of mycoheterotrophy. METHODS: We sequenced the internal transcribed spacer (ITS) regions of nuclear ribosomal (nr) DNA for mycobionts of Neottia plants. Furthermore, we selected one representative DNA sample from each fungal operational taxonomic unit (OTU) and used it to amplify the large subunit (LSU) nrDNA sequences. Phylogenetic analyses of Sebacinales (basidiomycetes), the dominant mycobiont of Neottia, were conducted and sample-based rarefaction curves generated for the observed mycobiont richness on each OTU. KEY RESULTS: Leafy and leafless species in Neottia were associated with Sebacinales Group Band Sebacinales Group A, respectively. The composition and specificity level of fungal partners varied among Neottia species. CONCLUSIONS: Fungal partner composition and specificity level changed with speciation in both leafy and leafless Neottia species. In particular, mycorrhizal associations likely shifted from Sebacinales Group B to Group A during the evolution from autotrophy to mycoheterotrophy. Partner shifts to Sebacinales Group A have also been reported in the evolution of mycoheterotrophy of other plant groups, suggesting that convergence to this fungal group occurs in association with the evolution of mycoheterotrophy. [ABSTRACT FROM AUTHOR]

The ubiquitous fungal order Sebacinales has the greatest diversity of mycorrhizal-types and is the earliest lineage containing such symbionts to diverge within the Basidiomycota. Two members of the Sebacinales, Piriformospora indica and Sebacina vermifera , have received most of the attention because of their growth-enhancing effects on a variety of host plants. Despite their worldwide distribution, axenic cultures of sebacinoids are extremely rare, and most of the knowledge gained thus far has been inferred using environmental and root tissue DNA. The global distribution of these fungi suggests host-tracking to novel habitats, sharing hosts within a habitat, and a general lack of host specificity. Their propensity as both saprotrophs and plant growth-promoting symbionts makes them strong candidates to be deployed for ecosystem restoration, bioremediation, and sustainable low-input agricultural efforts. [ABSTRACT FROM AUTHOR]

The interest in endophytic sebacinalean communities has been increasing during the last decade due to the increased knowledge about their symbiotic life style and potential role for ecosystem functioning. Although they are present in many ecosystems, their abundance in individual plant roots is very limited. This fact affects their study: they are difficult to isolate and to detect in root DNA samples. To advance knowledge of the forces that shape their distribution, we approached the parallel study of sebacinalean communities in roots and soil of grassland. Using a small-scale spatially explicit sampling design, we analysed the contribution of spatial position, soil properties, plant community and phylogenetic components to the variation of sebacinalean communities. The results revealed the presence of 11 operational taxonomic units (OTUs) and a high coincidence between root and soil communities: on an average a single-OTU per sample was recorded for both sample types. Spatial distance was found to mainly drive the distribution of Sebacinales in soil, whereas phylogenetic plus environmental signatures mainly drove their presence in roots. Independently of the sample type, we found clear evidence of environmental filtering caused by soil pH which, furthermore, seemed to control the presence of a specialized sebacinalean OTU. [ABSTRACT FROM AUTHOR]

Plant dependence on fungal carbon (mycoheterotrophy) evolved repeatedly. In orchids, it is connected with a mycorrhizal shift from rhizoctonia to ectomycorrhizal fungi and a high natural 13C and 15N abundance. Some green relatives of mycoheterotrophic species show identical trends, but most of these remain unstudied, blurring our understanding of evolution to mycoheterotrophy. We analysed mycorrhizal associations and 13C and 15N biomass content in two green species, Neottia ovata and N. cordata (tribe Neottieae), from a genus comprising green and nongreen (mycoheterotrophic) species. Our study covered 41 European sites, including different meadow and forest habitats and orchid developmental stages. Fungal ITS barcoding and electron microscopy showed that both Neottia species associated mainly with nonectomycorrhizal Sebacinales Clade B, a group of rhizoctonia symbionts of green orchids, regardless of the habitat or growth stage. Few additional rhizoctonias from Ceratobasidiaceae and Tulasnellaceae, and ectomycorrhizal fungi were detected. Isotope abundances did not detect carbon gain from the ectomycorrhizal fungi, suggesting a usual nutrition of rhizoctonia-associated green orchids. Considering associations of related partially or fully mycoheterotrophic species such as Neottia camtschatea or N. nidus-avis with ectomycorrhizal Sebacinales Clade A, we propose that the genus Neottia displays a mycorrhizal preference for Sebacinales and that the association with nonectomycorrhizal Sebacinales Clade B is likely ancestral. Such a change in preference for mycorrhizal associates differing in ecology within the same fungal taxon is rare among orchids. Moreover, the existence of rhizoctonia-associated Neottia spp. challenges the shift to ectomycorrhizal fungi as an ancestral pre-adaptation to mycoheterotrophy in the whole Neottieae. [ABSTRACT FROM AUTHOR]

Orchid mycorrhizal (OrM) symbionts play a key role in the growth of orchids, but the temporal variation and habitat partitioning of these fungi in roots and soil remain unclear., Temporal changes in root and rhizosphere fungal communities of Cypripedium calceolus, Neottia ovata and Orchis militaris were studied in meadow and forest habitats over the vegetation period by using 454 pyrosequencing of the full internal transcribed spacer ( ITS) region., The community of typical OrM symbionts differed by plant species and habitats. The root fungal community of N. ovata changed significantly in time, but this was not observed in C. calceolus and O. militaris. The rhizosphere community included a low proportion of OrM symbionts that exhibited a slight temporal turnover in meadow habitats but not in forests. Habitat differences in OrM and all fungal associates are largely attributable to the greater proportion of ectomycorrhizal fungi in forests., Temporal changes in OrM fungal communities in roots of certain species indicate selection of suitable fungal species by plants. It remains to be elucidated whether these shifts depend on functional differences inside roots, seasonality, climate or succession. [ABSTRACT FROM AUTHOR]

The article presents a study which demonstrates the total root associated fungal communities of sebacinales that are affected by land-use intensity. The study involves various soil types in Switzerland, like cambisol with a loamy texture, where all sites contained pasture, grew maize and winter-wheat or spelt. Results found several fungal communities such as Glarea lozoyensis, unclassified Sordariomycetes and Lasiosphaeriaceae, and Myrmecridium schulzeri.

While plant-fungal interactions are important determinants of plant community assembly and ecosystem functioning, the processes underlying fungal community composition are poorly understood., Here, we studied for the first time the root-associated eumycotan communities in a set of co-occurring plant species of varying relatedness in a species-rich, semi-arid grassland in Germany. The study system provides an opportunity to evaluate the importance of host plants and gradients in soil type and landscape structure as drivers of fungal community structure on a relevant spatial scale. We used 454 pyrosequencing of the fungal internal transcribed spacer region to analyse root-associated eumycotan communities of 25 species within the Asteraceae, which were sampled at different locations within a soil type gradient. We partitioned the variance accounted for by three predictors (host plant phylogeny, spatial distribution and soil type) to quantify their relative roles in determining fungal community composition and used null model analyses to determine whether community composition was influenced by biotic interactions among the fungi., We found a high fungal diversity (156 816 sequences clustered in 1100 operational taxonomic units ( OTUs)). Most OTUs belonged to the phylum Ascomycota (35.8%); the most abundant phylotype best-matched Phialophora mustea. Basidiomycota were represented by 18.3%, with Sebacina as most abundant genus. The three predictors explained 30% of variation in the community structure of root-associated fungi, with host plant phylogeny being the most important variance component. Null model analysis suggested that many fungal taxa co-occurred less often than expected by chance, which demonstrates spatial segregation and indicates that negative interactions may prevail in the assembly of fungal communities., Synthesis. The results show that the phylogenetic relationship of host plants is the most important predictor of root-associated fungal community assembly, indicating that fungal colonization of host plants might be facilitated by certain plant traits that may be shared among closely related plant species. [ABSTRACT FROM AUTHOR]

Plant growth-promoting and stress resilience-inducing root endophytic fungi represent an additional carbohydrate sink. This study aims to test if such root endophytes affect the sugar metabolism of the host plant to divert the flow of resources for their purposes. Fresh and dry weights of roots and shoots of tomato (Solanum lycopersicum) colonised by the closely related Serendipita indica and Serendipita herbamans were recorded. Plant carbohydrate metabolism was analysed by measuring sugar levels, by determining activity signatures of key enzymes of carbohydrate metabolism, and by quantifying mRNA levels of genes involved in sugar transport and turnover. During the interaction with the tomato plants, both fungi promoted root growth and shifted shoot biomass from stem to leaf tissues, resulting in increased leaf size. A common effect induced by both fungi was the inhibition of phosphofructokinase (PFK) in roots and leaves. This glycolytic-pacing enzyme shows how the glycolysis rate is reduced in plants and, eventually, how sugars are allocated to different tissues. Sucrose phosphate synthase (SPS) activity was strongly induced in colonised roots. This was accompanied by increased SPS-A1 gene expression in S. herbamans-colonised roots and by increased sucrose amounts in roots colonised by S. indica. Other enzyme activities were barely affected by S. indica, but mainly induced in leaves of S. herbamans-colonised plants and decreased in roots. This study suggests that two closely related root endophytic fungi differentially influence plant carbohydrate metabolism locally and systemically, but both induce a similar increase in plant biomass. Notably, both fungal endophytes induce an increase in SPS activity and, in the case of S. indica, sucrose resynthesis in roots. In leaves of S. indica-colonised plants, SWEET11b expression was enhanced, thus we assume that excess sucrose was exported by this transporter to the roots. ‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬., (Copyright © 2022. Published by Elsevier GmbH.)

Background: Phylogenetic studies, particularly those based on rDNA sequences from plant roots and basidiomata, have revealed a strikingly high genetic diversity in the Sebacinales. However, the factors determining this genetic diversity at higher and lower taxonomic levels within this order are still unknown. In this study, we analysed patterns of genetic variation within two morphological species, Sebacina epigaea and S. incrustans, based on 340 DNA haplotype sequences of independent genetic markers from the nuclear (ITS + 5.8S + D1/D2, RPB2) and mitochondrial (ATP6) genomes for 98 population samples. By characterising the genetic population structure within these species, we provide insights into species boundaries and the possible factors responsible for genetic diversity at a regional geographic scale. Results: We found that recombination events are relatively common between natural populations within Sebacina epigaea and S. incrustans, and play a significant role in generating intraspecific genetic diversity. Furthermore, we also found that RPB2 and ATP6 genes display higher levels of intraspecific synonymous polymorphism. Phylogenetic and demographic analyses based on nuclear and mitochondrial loci revealed three distinct phylogenetic lineages within of each of the morphospecies S. epigaea and S. incrustans: one major and widely distributed lineage, and two geographically restricted lineages, respectively. We found almost no differential morphological or ecological characteristics that could be used to discriminate between these lineages. Conclusions: Our results suggest that recombination and negative selection have played significant roles in generating genetic diversity within these morphological species at small geographical scales. Concordance between gene genealogies identified lineages/cryptic species that have evolved independently for a relatively long period of time. These putative species were not associated with geographic provenance, geographic barrier, host preference or distinct phenotypic innovations. [ABSTRACT FROM AUTHOR]

To study the diversity and phylogenetic structure of Sebacinales communities from eight vegetation communities along an altitudinal gradient in the Bavarian Alps ( Germany), we analysed 456 thalli or roots of plants. We detected 264 sebacinoid sequences, spanning the intergenic transcribed spacer region, 5.8S and D1/D2 regions of the nuclear r RNA gene, mostly using a nested PCR approach. Based on 97% sequence similarity, 73 Sebacinales molecular taxonomic units were found from 70 host species belonging to 44 plant families. Twenty-six molecular taxonomic units represented singletons, the most frequent of these being restricted exclusively to either wooded or grassland habitats. Although Sebacinales appear to occur in low abundance in plant roots, these microorganisms are phylogenetically diverse and widely spread in the ecosystems studied. Ordination analyses showed that land use, p H and humus content strongly influence the diversity and assembly of Sebacinales. In most cases, Sebacinales communities in ecosystems with extreme soil conditions or intensive land use exhibited significant phylogenetic clustering, whereas in undisturbed plant communities no trend was observed. These results suggest that ecosystem disturbance and environmental forces have an influence on the diversity and structure of Sebacinales community assembly over local and spatial scales. [ABSTRACT FROM AUTHOR]

The successful conversion of plant production systems from conventional resource-exhausting to sustainable strategies depends on knowledge-based management of environmental factors. Root-inhabiting fungi came more and more into focus because their hyphae connect in ideal manner resources and challenges of the surrounding with the plant. A paradigm for such root endophytes is presented by the basidiomycete Piriformospora indica. This fungus possesses a broad host spectrum and positively affects different aspects of plant performance. This so far unique combination of attributes makes P. indica and its close relatives among the Sebacinales very interesting tools for cultivation of various crops. This review will outline the different aspects required to apply this root endophyte in agri- and horticulture concerning plant growth, plant nutrition and plant defence or tolerance thereby explaining what is known about the biological basis for the observed effects. Open questions and challenges for successful inoculum production and application will be discussed. [ABSTRACT FROM AUTHOR]