Hagen, J. A. | Search bioRxiv

bioRxiv2023

Arbuscular mycorrhiza convey significant plant carbon to a diverse hyphosphere microbial food web and mineral-associated organic matter

O_LIArbuscular mycorrhizal fungi (AMF) transport substantial plant carbon (C) that serves as a substrate for other soil organisms, a precursor of soil organic matter (SOM), and a driver of soil microbial dynamics. Using two-chamber microcosms where an air gap isolated AMF from roots, we 13CO2-labeled Avena barbata for six weeks and measured. the C Rhizophagus intraradices transferred to SOM and hyphosphere microorganisms. C_LIO_LINanoSIMS imaging, IRMS, 13C NMR, and SOM density fractionation showed hyphae and roots had similar 13C enrichment. AMF transferred 0.77 mg C per g of soil (increasing total C by 2%); 33% was found in occluded or mineral-associated pools, primarily as carbohydrates. C_LIO_LIIn the AMF hyphosphere, there was no overall change in community diversity but 36 bacterial ASVs significantly changed in relative abundance. With stable isotope probing (SIP)-enabled shotgun sequencing, we found taxa from the Solibacterales, Sphingobacteriales, Myxococcales and Nitrososphaerales (ammonium oxidizing archaea) were highly enriched in AMF-imported 13C (>20 atom%). Mapping 13C-enriched metagenome-assembled genomes to total ASVs showed at least 92 bacteria and archaea were significantly 13C-enriched. C_LIO_LIOur results illustrate the quantitative impact of hyphal C transport on the formation of potentially protective SOM pools and indicate microbial roles in the AMF hyphosphere soil food web. C_LI

microbiology↗

bioRxiv2020

Routes to Roots: Direct Evidence of Water Transport by Arbuscular Mycorrhizal Fungi to Host Plants

Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with 80% of surveyed land plant species and are well-recognized for accessing and transferring nutrients to plants1. Yet AMF also perform other essential functions, notably improving plant-water relations2. Some research attributes the role of AMF in plant-water relations solely to enhancing plant nutrition and osmoregulation for plants partnered with AMF3,4,5, while indirect evidence suggests AMF may transport water to plants1,6,7. Here, we used isotopically-labeled water and a fluorescent dye to directly track and quantify water transport by AMF to plants in a greenhouse experiment. We specifically assessed whether AMF can access water in soil unavailable to plants and transport it across an air gap to host plants. Plants grown with AMF that had access to a physically separated 18O-labeled water source transpired twice as much, and this transpired water contained three times as much label compared to plants with AMF with no access to the separated labeled water source. We estimated that water transported by AMF could explain 46.2% of the water transpired. In addition, a fluorescent dye indicated that water was transported via an extracytoplasmic hyphal pathway.

microbiology↗