Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, United States; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States; Department of Plant Biology, Michigan State University, East Lansing, United States
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States; Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University, Göttingen, Germany; Centre of Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Toruń, Toruń, Poland
Natalie Vande Pol
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, United States
Nathaniel E Ostrom
Department of Integrative Biology, Michigan State University, East Lansing, United States; DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, United States
Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, United States; DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, United States; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States; Department of Plant Biology, Michigan State University, East Lansing, United States
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, United States; DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, United States; Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, United States
Mutualistic interactions between free-living algae and fungi are widespread in nature and are hypothesized to have facilitated the evolution of land plants and lichens. In all known algal-fungal mutualisms, including lichens, algal cells remain external to fungal cells. Here, we report on an algal–fungal interaction in which Nannochloropsis oceanica algal cells become internalized within the hyphae of the fungus Mortierella elongata. This apparent symbiosis begins with close physical contact and nutrient exchange, including carbon and nitrogen transfer between fungal and algal cells as demonstrated by isotope tracer experiments. This mutualism appears to be stable, as both partners remain physiologically active over months of co-cultivation, leading to the eventual internalization of photosynthetic algal cells, which persist to function, grow and divide within fungal hyphae. Nannochloropsis and Mortierella are biotechnologically important species for lipids and biofuel production, with available genomes and molecular tool kits. Based on the current observations, they provide unique opportunities for studying fungal-algal mutualisms including mechanisms leading to endosymbiosis.
