Unity in diversity: functional insights into the ancient partnerships between plants and fungi

Dr Katie Field’s seminar explored her work on ancient plant-fungal symbioses during the colonisation of land by plants, describing the range of methods used to unravel the nature of these early associations between plants and fungi.

Mutualistic associations between plants and symbiotic fungi are documented throughout the plant kingdom, from bryophytes through to vascular plants. It is thought that these mutualisms were present from early in plant evolutionary history and could have played a key role in facilitating the colonisation of land. Even more exciting, is the suggestion that a range of fungal groups formed associations with plants at these times, with evidence for associations between bryophytes and both Glomeromycotina and Mucoromycotina.

Dr Field’s team have demonstrated experimentally that the balance of nutrient and carbon exchange between the fungi and plant depends on the identity of the fungal partner.  Experiments using present day plants and fungi were conducted under contemporary CO2 levels and the raised CO2 conditions that were present in the Ordovician. Under the higher CO2 conditions, more carbon is transferred from plants to their fungal partners. The reciprocal nutrient return from the fungi varies between fungal groups: plants associated with Mucoromycotina do not receive a higher level of nutrients, whereas plants associated with Glomeromycotina receive a higher nutrient return under the raised CO2. Therefore, carbon-nutrient exchange efficiency is enhanced for plants associated with Glomeromycotina under higher CO2 conditions. These results have key implications for global biogeochemical cycling during the Ordovician: models suggest that the rates of O2 release and CO2 drawdown would have been higher under a scenario where Glomeromycotina symbioses dominated over Mucoromycotina symbioses.

It was fascinating to hear of the diversity and prevalence of mutualistic plant-fungal associations across the plant kingdom, and their presence from the earliest stages of plant evolutionary history. Today bryophytes may often be overlooked as examples of primitive plants, but this research suggests that they played a global role as engineers of the terrestrial biosphere, aided by fungal mutualisms.

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Emily Warner is a DPhil Candidate in the Department of Plant Sciences through the NERC Doctoral Training Partnership in Environmental Research

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