Evidence for resource transfer via common endophyte networks.

Area of Science:

• Plant-Fungal Interactions
• Ecosystem Ecology
• Symbiotic Networks

Background:

• Fungal symbionts, including mycorrhizal fungi and endophytes, are crucial for plant development and ecosystem health.
• Mycorrhizal fungi form common mycorrhizal networks (CMNs) facilitating inter-plant resource transfer (e.g., nitrogen, carbon).
• The capacity of endophytes to form similar networks (common endophyte networks, CENs) and transfer resources remained largely unexplored.

Purpose of the Study:

• To investigate whether fungal endophytes can form common endophyte networks (CENs).
• To determine if endophytes can transfer soil resources (nitrogen, carbon, water) between connected plants via CENs.
• To assess how host plant presence influences endophytic resource transfer.

Main Methods:

• Established a common endophyte network (CEN) experiment using Arabidopsis thaliana and three diverse endophytes (Trichoderma viride, Mucor hiemalis, Fusarium temperatum) in split petri dishes.
• Utilized isotopically labeled resources (¹⁵N-amino acid, ¹³C-amino acid, ¹⁵N-ammonium, deuterated water) to trace resource transfer from donor to receiver plants.
• Compared resource transfer efficiency with single versus multiple host plants, with physically separated root systems to isolate network effects from competition.

Main Results:

• Confirmed that tested endophytes can form CENs and effectively transfer growth-limiting soil resources from donor to receiver plants.
• Fusarium temperatum significantly boosted plant growth (38%) and nitrogen uptake (55% ¹⁵N enrichment from amino acids).
• Trichoderma viride facilitated amino acid-derived carbon transport (2.83% ¹³C enrichment), and resource transfer varied with the number of host plants.

Conclusions:

• Non-mycorrhizal fungal endophytes can establish networks analogous to CMNs, facilitating inter-plant resource translocation.
• Common endophyte networks (CENs) represent a newly identified symbiotic function of endophytes, contributing to plant growth and resource dynamics.
• Endophytic network functioning is responsive to host plant presence, highlighting the complexity of plant-fungal interactions in ecosystems.