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A Core Gene Set Describes the Molecular Basis of Mutualism and Antagonism in Epichloë spp.

March 2015 , Volume 28 , Number  3
Pages  218 - 231

Carla J. Eaton,1 Pierre-Yves Dupont,1 Peter Solomon,2 William Clayton,1 Barry Scott,1 and Murray P. Cox1

1Institute of Fundamental Sciences and the Bio-Protection Research Centre, Massey University, Palmerston North, 4442, New Zealand; 2Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, ACT 0200, Australia

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Accepted 2 December 2014.

Beneficial plant–fungal interactions play an important role in the ability of plants to survive changing environmental conditions. In contrast, phytopathogenic fungi fall at the opposite end of the symbiotic spectrum, causing reduced host growth or even death. In order to exploit beneficial interactions and prevent pathogenic ones, it is essential to understand the molecular differences underlying these alternative states. The association between the endophyte Epichloë festucae and Lolium perenne (perennial ryegrass) is an excellent system for studying these molecular patterns due to the existence of several fungal mutants that have an antagonistic rather than a mutualistic interaction with the host plant. By comparing gene expression in a wild-type beneficial association with three mutant antagonistic associations disrupted in key signaling genes, we identified a core set of 182 genes that show common differential expression patterns between these two states. These gene expression changes are indicative of a nutrient-starvation response, as supported by the upregulation of genes encoding degradative enzymes, transporters, and primary metabolism, and downregulation of genes encoding putative small-secreted proteins and secondary metabolism. These results suggest that disruption of a mutualistic symbiotic interaction may lead to an elevated uptake and degradation of host-derived nutrients and cell-wall components, reminiscent of phytopathogenic interactions.

© 2015 The American Phytopathological Society