Fungal Protein Allows Beneficial Colonization in Populus
The soil environment surrounding plant roots is filled with bacteria and fungi, both harmful and beneficial, many of which attempt to colonize root tissues to gain access to and use plant nutrients. In response, plant hormones such as jasmonic acid (JA) mediate the plant’s defense signaling system. By altering this pathway, some microorganisms can gain entry into the plant root cells and promote colonization. Investigating the symbiotic relationship between the bioenergy feedstock tree Populus trichocarpa and the beneficial fungus Laccaria bicolor, researchers at Oak Ridge National Laboratory found that a fungal protein essential for root establishment (called MiSSP7; Mycorrhiza-induced Small Secreted Protein 7) interacts with a plant-produced protein within the host plant nuclei to promote symbiosis. While both pathogenic and mutualistic fungi use fungal “effector” proteins to facilitate colonization, the results suggest how the mechanisms used to overcome the plant’s defenses differ between these two types of organisms, furthering understanding of how L. bicolor alters the plant’s response to JA and allows formation of symbiotic relationships.
Plett, J. M., Y. Daguerre, S. Wittulsky, A. Vayssières, A. Deveau, S. J. Melton, A. Kohler, J. L. Morrell-Falvey, A. Brun, C. Veneault-Fourrey, and F. Martin. 2014. “Effector MiSSP7 of the Mutualistic Fungus Laccaria bicolor Stabilizes the Populus JAZ6 Protein and Represses Jasmonic Acid (JA) Responsive Genes,” Proceedings of the National Academy of Sciences (USA) 111(22), 8299-304. DOI: 10.1073/pnas.1322671111.