A mutualistic symbiosis between a dark septate endophytic fungus, Heteroconium chaetospira, and a nonmycorrhizal plant, Chinese cabbage
| Autor: | Kazuhiko Narisawa, Fumiaki Usuki |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Sucrose
Magnetic Resonance Spectroscopy Physiology Nitrogen Microorganism Fungus Brassica Plant Roots Ascomycota Mycorrhizal fungi Mutualistic symbiosis Ergosterol Botany Genetics Mannitol Biomass Carbon Radioisotopes Amino Acids Symbiosis Molecular Biology Ecology Evolution Behavior and Systematics biology fungi food and beverages Cell Biology General Medicine Endophytic fungus biology.organism_classification Carbon transfer Carbon Heteroconium chaetospira Fungal penetration |
| Zdroj: | Mycologia. 99(2) |
| ISSN: | 0027-5514 |
| Popis: | Symbiotic microorganisms, such as mycorrhizal fungi, are known to associate with most plants; however members of the Cruciferae are an exception. We investigated nutrient exchange between a dark septate endophytic fungus, Heteroconium chaetospira, and Chinese cabbage plants (Cruciferae) in vitro. Chinese cabbage could not use some amino acids, while the fungus-treated plants were able to use all of the nitrogen forms provided. To demonstrate that nitrogen transfer occurs between the fungus and the host plant, we used a hydrophobic polytetrafluoroethylene (PTFE) membrane compartment system, which restricts diffusion and mass flow of ions and allows only fungal penetration. Our results strongly suggest that H. chaetospira provided nitrogen to the plant, rather than the plant mineralizing available organic nitrogen. In addition carbon transfer from the host plant to the fungus was demonstrated with HPLC and (l3)CO2-labeling experiments. When H. chaetospira colonized host plant roots under low glucose condition, ergosterol content in culture pot (as an index of fungal biomass) increased significantly compared to the fungal treatment without a host plant. Sucrose concentration in the host root significantly decreased as a result of fungal colonization, and mannitol (a specific carbon source to fungal cells) increased in the roots. Sucrose and mannitol in the host root treated with the fungus were labeled clearly by 13C after 1C-labeled CO2 was provided to the plant. These results suggest that the fungus obtained carbon, mainly as sucrose, from the host plant. We show for the first time the existence of a fungus establishing a mutualistic association with a nonmycorrhizal Cruciferae plant. |
| Databáze: | OpenAIRE |
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