Biology subjects

Pressel, S.

Publications and source records attributed to Pressel, S..

6 recordsLinked to original sources

bioRxiv2025

Common symbiotic signalling pathway not essential for formation of functional mutualisms with endophytic fungi

Most plants form mutualistic symbioses with soil fungi, including arbuscular mycorrhizal (AM) fungi. These fungi usually transfer soil nutrients to plants and assimilate carbon from host plant photosynthesis. Recently, Mucoromycotina fine root endophytes (MFRE) were identified as nutritionally mutualistic and widespread fungal symbionts of plants, establishing MFRE as a new class of mycorrhizal fungi. However, the regulatory mechanisms for MFRE symbioses are completely unknown. Other symbionts, like AM fungi, use the Common Symbiotic Signalling Pathway (CSSP) to establish symbiosis. To explore whether MFRE interactions also involve this pathway, we cultured MFRE with CSSP mutants of Medicago truncatula which show impaired AM symbioses and tracked carbon and nutrient transfers using isotope tracers. Results show no differences in root colonization or nutrient exchange, suggesting MFRE symbioses are regulated by different molecular mechanisms. This finding highlights the unique nature of MFRE symbiosis, broadening our understanding of diverse fungal symbioses and their evolutionary significance.

microbiology↗

bioRxiv2024

Preferential assimilation, metabolism, and transfer of organic nitrogen to host plants by Mucoromycotina 'fine root endophytes'

O_LIMucoromycotina fine root endophytes (MFRE) are an understudied group of plant fungal symbionts that usually co-occur with arbuscular mycorrhizal fungi. The functional significance of MFRE in plant nutrition remains under-explored, particularly their role in plant N assimilation from the variety of sources typically found in soils. C_LIO_LIUsing four 15N-labelled N sources to track N transfer between MFRE and Plantago lanceolata, applied singly and in tandem, we investigated N source discrimination, preference, and transfer to host plants by MFRE. We traced movement of 14C from plants to MFRE to determine the impact of N source type on plant C allocation to MFRE. C_LIO_LIWe found MFRE preferentially transferred N derived from glycine and ammonium to plant hosts over that derived from nitrate and urea, regardless of other N sources present. MFRE mycelium supplied with glycine and ammonium contained more plant-derived carbon than those supplied with other N sources. C_LIO_LIWe show that MFRE directly assimilates and metabolises organic compounds, retaining C to meet its own metabolic requirements and transferring N to plant hosts. Our findings highlight diversity in function of endomycorrhizal associations with potentially profound implications for our understanding of the physiology and ecology of plant-fungal symbioses. C_LI

plant biology↗

bioRxiv2023

Assessing above and belowground recovery from ammonium sulfate addition and wildfire in a lowland heath: mycorrhizal fungi as potential indicators

Atmospheric pollution containing soil-nitrifying ammonium sulphate is affecting semi-natural ecosystems worldwide. Long-term additions of ammonium sulphate on nitrogen (N)-limited habitats such as heathlands increase climate stress affecting recovery from wildfires. Yet although heathland vegetation largely depends on ericoid mycorrhizal fungi (ErM) to access soil N, we lack a detailed understanding of how prolonged exposure to ammonium sulphate may alter ErM community composition and host plants reliance on fungal partners following wildfire and substantial reductions in ammonium sulphate pollution. Effects on ecosystem processes, particularly carbon stores, also remain uncertain. Ammonium sulphate additions occurred bi-weekly for five years after a 2006 wildfire burnt a UK heathland. Ten years after the treatments ceased (2021), we measured vegetation structure, lichen and lichen photobiont composition, soil characteristics, ErM colonisation, ErM diversity in roots and soil, and assessed their potential as recovery indicators. We found heather height and density, and moss groundcover, were greater in N-enriched plots. Lichen community indices showed significant treatment effects without photobiont differences. Soil pH and Mg, and the proportion of putative ErM fungi in soil were significantly lower in treated plots while soil cation exchange capacity was significantly higher. Increases in soil pH were positively correlated to soil ErM abundance. Soil carbon stock measures were variable and negatively related with soil ErM. Our results indicate that atmospheric pollution following fire can have significant lingering effects and mycorrhizal fungi diversity are a novel and effective ecological tool to assess ecosystem recovery on heathlands. IMPLICATIONS FOR PRACTICEO_LIRecovery of heathlands from wildfire and atmospheric pollution may require decadal scales. Conventional restoration assessment tools lack critical understanding of belowground soil and mycorrhizal fungi interactions and nutritional feedback loops with aboveground hosts. C_LIO_LIGiven that ericoid mycorrhizal fungi (ErM) communities are key nutrient regulators of resilient heathlands, we recommend baseline measurements of ErM diversity and abundance in both soil and dominant plant roots be added to the recovery assessment toolkit prior to commencing restoration or management plans. C_LIO_LIWhat defines ErM recovery, and disentangling effects of ammonium sulphate pollution and fire, remain open questions which only long-term field experiments across pollution gradients will address. C_LI

ecology↗

bioRxiv2020

Carbon for nutrient exchange between the lycophyte, Lycopodiella inundata and Mucoromycotina fine root endophytes is unresponsive to high atmospheric CO2 concentration

Background and AimsNon-vascular plants associating with arbuscular mycorrhizal (AMF) and Mucoromycotina fine root endophyte (MFRE) fungi derive greater benefits from their fungal associates under higher atmospheric [CO2] than ambient, however nothing is known about how changes in [CO2] affects MFRE function in vascular plants. MethodsWe measured movement of phosphorus (P), nitrogen (N) and carbon (C) between the lycophyte, Lycopodiella inundata and Mucoromycotina fine root endophyte fungi using 33P-orthophosphate, 15N-ammonium chloride and 14CO2 isotope tracers under ambient and elevated atmospheric [CO2] concentrations of 440 and 800 ppm, respectively. Key ResultsTransfer of 33P and 15N from MFRE to plant were unaffected by changes in [CO2]. There was a slight increase in C transfer from plant to MFRE under elevated [CO2]. ConclusionsOur results demonstrate that the exchange of C-for-nutrients between a vascular plant and Mucoromycotina FRE is largely unaffected by changes in atmospheric [CO2]. Unravelling the role of MFRE in host plant nutrition and potential C-for-N trade changes between symbionts under varying abiotic conditions is imperative to further our understanding of the past, present and future roles of diverse plant-fungal symbioses in global ecosystems.

plant biology↗

bioRxiv2020

Phenology and function in lycopod-Mucoromycotina symbiosis

Lycopodiella inundata is a lycophyte with a complex life cycle. The gametophytes and the juvenile, mature and retreating sporophytes form associations with Mucoromycotina fine root endophyte (MFRE) fungi, being mycoheterotrophic as gametophytes and mutualistic as mature sporophytes. However, the function of the symbiosis across juvenile and retreating sporophyte life stages remains unknown. We measured carbon-for-nutrient exchanges between L. inundata and MFRE across the transition from newly emerging sporophytes to mature sporophytes and in retreating adult sporophytes. We show MFRE fungi play distinct functional roles at each plant life stage, with evidence of bidirectional exchange of plant C for fungal acquired nutrients (N and P) between mature adult and retreating adult sporophytes and fungi, but no transfer of plant C to fungi and little fungal-acquired nutrient gain in juvenile sporophytes. Furthermore, we show that these functional stages correspond with different cytologies of colonisation. Our results show that MFRE have considerable plasticity in their interactions with the host plant which is related to the developmental stage of the host. This highlights the need for further research into symbiotic fungal function across plant life histories.

plant biology↗

bioRxiv2019

Mucoromycotina fine root endophyte fungi form nutritional mutualisms with vascular plants.

Fungi and plants have engaged in intimate symbioses that are globally widespread and have driven terrestrial biogeochemical processes since plant terrestrialisation >500 Mya. Recently, hitherto unknown nutritional mutualisms involving ancient lineages of fungi and non-vascular plants have been discovered. However, their extent and functional significance in vascular plants remains uncertain. Here, we provide first evidence of abundant carbon-for-nitrogen exchange between an early-diverging vascular plant (Lycopodiaceae) and Mucoromycotina (Endogonales) fine root endophyte regardless of changes in atmospheric CO2 concentration. Furthermore, we provide evidence that the same fungi also colonize neighbouring non-vascular and flowering plants. These findings fundamentally change our understanding of the evolution, physiology, interrelationships and ecology of underground plant-fungal symbioses in terrestrial ecosystems by revealing an unprecedented nutritional role of Mucoromycotina fungal symbionts in vascular plants.

plant biology↗