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Poster

Session: Session 2 Presenting Authors at Posters (Evens)

P-154 - Structural and functional investigation of zinc-binding effectors in wheat stem rust

Thursday, July 17, 2025
13:30 - 15:15  
Location: Confex Hall 3
Effector Interference Mechanisms
Stem rust caused by Puccinia graminis f. sp. tritici, is one of the most devastating fungal diseases affecting wheat crops worldwide. Similar to other pathogens, stem rust delivers effector proteins into wheat plants as part of its infection strategy. We used AlphaFold2 to predict the structures of effectors secreted by the causative agent of the wheat stem rust and grouped these into clusters of similar structural families. This analysis revealed that some of the largest structural classes of effectors were predicted to bind zinc ions through cysteine and histidine coordination. These included the structural families containing the recognised effectors AvrSr27, AvrSr22, AvrSr13 and AvrSr33. In this study, we expressed and purified these proteins in order to test these predictions. We conducted a series of biochemical assays, including the PAR (4-(2-pyridylazo) resorcinol) assay, ICP-MS (inductively coupled plasma mass spectrometry), and MST (micro-scale thermophoresis), which confirmed that these effector proteins do indeed all bind to zinc ions. We experimentally determined the crystal structure of the AvrSr33 effector, which exhibited two zinc binding sites. We are now utilising the structure to understand the requirements for Sr33 recognition.