A cytotoxic effector from the wheat pathogen Zymoseptoria tritici
G. KETTLES (1), K. Kanyuka (1), J. Rudd (1) (1) Rothamsted Research, United Kingdom

Zymoseptoria tritici is amongst the most prevalent and damaging fungal pathogens of wheat throughout the world. During early wheat leaf colonisation, there is minimal induction of host defence responses. Later, there is a switch to necrotrophy, accompanied by defence gene induction and host cell death. We recently identified ~100 candidate Z. tritici effectors that show peak expression at the onset of necrotrophy during infection of susceptible wheat. To understand the molecular function of these effectors, we cloned and expressed 64 candidates in leaves of the model plant Nicotiana benthamiana using Agrobacterium-mediated transient expression. This screen identified 15 proteins that induced cell death or chlorosis in this non-host species. Of these 15, the majority required localisation to the apoplastic space for their activity and most functioned light-dependently. One distinction was a candidate effector (Zt6), which is a putative secreted fungal ribonuclease that induced cell death in a secretion- and light-independent manner. Unlike the other 14 proteins, we were unable to recover full-length Zt6 protein from either yeast or bacterial recombinant expression systems, suggesting broad-ranging cellular toxicity. Site-directed mutagenesis identified regions of this protein important for full toxicity to both yeast and plant cells, and revealed that that the Zt6 ribonuclease has characteristics reminiscent of the ribosome-inactivating proteins (RIPs).

Abstract Number: P6-144
Session Type: Poster