Identification and characterisation of a new flax rust effector
A. CATANZARITI (1), S. Williams (1), C. Anderson (1), J. Ellis (2), P. Dodds (2), A. Hardham (1), D. Jones (1) (1) Research School of Biology, Australian National University, Australia; (2) CSIRO Agriculture, Australia

Plant pathogens secrete effector proteins during colonisation of their host to promote disease. However, the precise roles they play during infection is largely unknown, particularly for fungal effectors. Flax rust is a biotrophic fungus that causes disease on flax. We recently identified the flax rust effector AvrM14, which is recognised by the flax resistance proteins M1 and M4, and contains a putative Nudix motif. Using X-ray crystallography, we determined that the structure of AvrM14 is closely related to known Nudix hydrolases, a diverse family of enzymes that hydrolyse a wide-range of pyrophosphates. Given that Nudix enzymes can have NADH pyrophosphorylase activity, we tested whether AvrM14 could suppress production of PAMP-triggered reactive oxygen species (ROS). When transiently expressed in tobacco, AvrM14 and the virulence form, avrM14, suppressed both flg22 and chitin-triggered ROS bursts. This activity was dependent on the key catalytic site glutamate residue (E82), suggesting that AvrM14 plays a role in suppressing plant immunity. To investigate recognition specificity by the flax resistance proteins, polymorphic residues between AvrM14 and avrM14 were mutated. Preliminary analysis suggests that different residues are important for recognition by M1 compared to M4. However, for both resistance proteins, recognition was independent of the active site residue E82, suggesting it does not depend on Nudix hydrolase activity.

Abstract Number: P9-244
Session Type: Poster