Effector biology of Zymoseptoria tritici during interactions with wheat and with non-host plants.
G. KETTLES (1), R. King (2), J. Hooper (2), W. Skinner (3), J. Hargreaves (4), K. Hammond-Kosack (2), B. Fraaije (2), J. Rudd (1) (1) Rothamsted Research, Harpenden, United Kingdom; (2) Rothamsted Research, United Kingdom; (3) Long Ashton Resaerch Station, , United Kingdom; (4) Long Ashton Research Station, United Kingdom

The fungus Zymoseptoria tritici is a strictly apoplastic, host-specific pathogen of wheat leaves and causal agent of Septoria tritici blotch (STB) disease. Early infection is symptomless and requires the function of a secreted LysM effector protein to suppress chitin-triggered immunity. The subsequent switch to necrotrophy is accompanied by “defence” gene induction, host cell death and coincides with elevated expression of many other candidate fungal effector proteins. To dissect the putative functions of these effectors during interactions with both wheat and the model non-host plant Nicotiana benthamiana, we cloned and functionally characterised 64 candidate Z. tritici effectors that show peak expression at the onset of necrotrophy on susceptible wheat. Whilst only one protein caused a clear phenotype in wheat leaves, surprisingly, 15 proteins induced cell death or chlorosis in N. benthamiana when transiently expressed using Agrobacterium. Of these 15, the majority required localisation to the apoplastic space for their activity and most functioned in a light-dependent manner. Furthermore, cell death induced by three effectors required the receptor-like kinases (RLKs) NbBAK1 and NbSOBIR1. Our results indicate widespread recognition of apoplastic effectors from a wheat-infecting fungal pathogen in a taxonomically distant non-host plant species presumably by cell surface immune receptors. This suggests that plasma membrane-based recognition of multiple non-adapted pathogen effectors could contribute towards non-host resistance against apoplastic pathogens.

Abstract Number: S6-3
Session Type: Special Session