Symbiotic Relationship with Fungi Benefits Bioenergy Feedstock Poplar

This exchange is essential for continued growth and productivity of forest trees, especially in nutrient-poor soils.

The Science

The forest soil environment is teeming with microbial communities, including a group of mutualistic fungi known as the ectomycorrhizae. These organisms develop a close association with tree roots, establishing an exchange of nutrients and sugars essential for the health of both plant and microbe. While this phenomenon has been known for a long time, the signaling and regulatory mechanisms of this exchange are poorly understood. Researchers at the DOE Oak Ridge National Laboratory, as part of an international collaboration, have identified and characterized a protein called Mycorrhizal Induced Small Secreted Protein 7 (MiSSP7) that is secreted from the ectomycorrhizal fungus Laccaria bicolor in response to signals diffused from the roots of poplar trees, a promising bioenergy feedstock. They found that this very small protein is imported into the nucleus of the host plant cell where it alters the expression of certain plant genes, similar to the manner in which fungal pathogens work. The result is a “reprogram-ming” of plant cells, through which a beneficial, symbiotic relationship between fungus and plant is established. This relationship enhances growth and productivity of the tree. Understanding the underlying mechanism will help address diverse DOE missions, including bioenergy production, environmental remediation, and carbon cycling and sequestration.

References

Plett, J. M., M. Kemppainen, S. D. Kale, A. Kohler, V. LeguĂ©, A. Brun, B. M. Tyler, A. G. Pardo, and F. Martin. 2011. “A Secreted Effector Protein of Laccaria bicolor Is Required for Symbiosis Development,” Current Biology 21, 1197&ndash1203. DOI:10.1016/j.cub.2011.05.033.