A mutualistic symbiosis between a dark septate endophytic fungus,Heteroconium chaetospira,and a nonmycorrhizal plant, Chinese cabbage

Abstract

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.

Novel Root Fungal Consortium Associated with a Dominant Desert Grass

“…Some of these fungi, notably mycorrhizal fungi, have received extensive study, but accumulating evidence indicates that many of the fungi associated with plant roots are dark septate fungi (DSF). These fungi are usually described as endophytes, whose functions have only recently been studied (43,44,76). DSF comprise a taxonomically diverse group (34, 37) characterized by melanized septate hyphae.…”

Entomopathogen Metarhizium anisopliae promotes the early development of peanut root

“…Several hypotheses and previous studies have provided incomprehensive explanations. The interaction between fungi and plants is beneficial to plants, through improving the ability of the plant to tolerate unfavourable conditions (Hesse et al 2003;Rodríguez et al 2008), protecting the plant from diseases that can damage it (Flori et al 1993;Ownley et al 2008), warding off insect pests (Cherry et al 1999(Cherry et al , 2004Powell et al 2007), supplying nutrients to the plant through the transfer of nitrogen and the uptake of phosphorus and other minerals (Usuki & Narisawa 2007;Behie et al 2012).…”

Diversidad, ecología e importancia potencial de los hongos endófitos septados obscuros en México

“…Upson et al (2009a) postulan que es probable que la mayoría de los DSE utilicen enzimas proteolíticas para mineralizar el N orgánico y con ello hacerlo disponible para la planta (Caldwell et al, 2000). Existen evidencias de que el DSE Heteroconium chaetospira (Grove) M.B.Ellis transfi ere N proveniente de aminoácidos, como la leucina, a la planta Brassica capestris L. a cambio de fuentes de carbono (Usuki y Narisawa, 2007). Asimismo, otros estudios proponen que los DSE promueven el uso efi ciente de los nutrimentos cuando existen elevadas concentraciones de CO 2 (Alberton et al, 2010), lo cual sugiere que los DSE pueden regular la respuesta de la planta a los cambios bióti-cos y abióticos del ecosistema (Zhang et al, 2013).…”