Neotyphodium lolii induces a limited host defence response by Lolium perenne

We have identified three proteins specifically expressed during the interaction between N. lolii and L. perenne in natural compatible associations. Two are pathogenesis-related PR-10 proteins, part of a ubiquitous plant response to pathogens. We have identified seven different L. perenne PR-10 genes and found that endophyte infection increases PR-10 transcript levels, but only mildly. Furthermore, PR-10 mRNA levels also increase in a dysfunctional symbiosis, but the two identified PR-10 proteins are absent. This suggests that part of the regulation of protein expression is at the level of translation and that PR-10 proteins could be required for the symbiosis to be functional. A third symbiosis-specific protein is a very highly expressed N. lolii superoxide dismutase. Such enzymes neutralise superoxide formed by plants as a defence mechanism. Our results suggest that N. lolii elicits a limited host defence, comparable to that elicited by arbuscular mycorrhiza. Keywords: Neotyphodium lolii, Lolium perenne, host response, proteomics, gene expresion, pathogenesis related protein PR-10, fungal superoxide dismutase