Biology subjects

Ericsson, D. J.

Publications and source records attributed to Ericsson, D. J..

4 recordsLinked to original sources

bioRxiv2023

AvrSr27 is a zinc-bound effector with a modular structure important for immune recognition

Stem rust, caused by the fungal pathogen Puccinia graminis f. sp.tritici (Pgt) is a major threat for wheat production and global food security. Central to the success of Pgt is the secretion of proteinaceous effectors that promote infection and colonisation, while immunity in wheat is driven by receptor-mediated recognition of these effectors resulting in pathogen avirulence. Here, we report the crystal structure of the cysteine-rich effector AvrSr27, the third experimentally derived structure of a Pgt effector. The AvrSr27 structure reveals a novel {beta}-strand rich modular fold consisting of two structurally similar domains and confirms the poor prediction we obtained from the AlphaFold2-derived model. The highly prevalent cysteine residues within the protein facilitate the co-ordination of 4 zinc molecules. Utilising the structure, we show that the N-terminal domain of AvrSr27 is sufficient for immune recognition and interaction by Sr27. The 7-cys motif sequence in each AvrSr27 domain, which facilitates zinc binding, was also found in two haustorially-expressed, structurally homologous Pgt proteins. Remarkably, despite relatively low sequence identity, we show that these proteins can associate with Sr27 and trigger cell death in heterologous systems and wheat protoplasts, albeit weaker than AvrSr27. Collectively, our findings have important implications for the field embarking on bespoke engineering of immunity receptors as solutions to plant disease.

plant biology↗

bioRxiv2023

Plant pathogenic fungi hijack phosphate starvation signaling with conserved enzymatic effectors

Phosphate availability modulates plant immune function and regulates interactions with beneficial, phosphate-providing, microbes. Here, we describe the hijacking of plant phosphate sensing by a family of Nudix hydrolase effectors from pathogenic Magnaporthe oryzae and Colletotrichum fungi. Structural and enzymatic analyses of the Nudix effector family demonstrate that they selectively hydrolyze inositol pyrophosphates, a molecule used by plants to monitor phosphate status and regulate starvation responses. In M. oryzae, gene deletion and complementation experiments reveal that the enzymatic activity of a Nudix effector significantly contributes to pathogen virulence. Further, we show that this conserved effector family induces phosphate starvation signaling in plants. Our study elucidates a molecular mechanism, utilized by multiple phytopathogenic fungi, that manipulates the highly conserved plant phosphate sensing pathway to exacerbate disease. One-Sentence SummaryA family of conserved enzyme effectors from pathogenic fungi manipulate plant phosphate sensing to promote infection.

plant biology↗

bioRxiv2021

The structural repertoire of Fusarium oxysporum f. sp. lycopersici effectors revealed by experimental and computational studies

Plant pathogens secrete proteins, known as effectors, that function in the apoplast or inside plant cells to promote virulence. Effector recognition by cell-surface or cytosolic receptors results in the activation of defence pathways and plant immunity. Despite their importance, our general understanding of fungal effector function and recognition by immunity receptors remains poor. One complication often associated with effectors is their high sequence diversity and lack of identifiable sequence motifs precluding prediction of structure or function. In recent years, several studies have demonstrated that fungal effectors can be grouped into structural classes, despite significant sequence variation and existence across taxonomic groups. Using protein x-ray crystallography, we identify a new structural class of effectors hidden within the secreted in xylem (SIX) effectors from Fusarium oxysporum f. sp. lycopersici (Fol). The recognised effectors Avr1 (SIX4) and Avr3 (SIX1) represent the founding members of the Fol dual-domain (FOLD) effector class, with members containing two distinct domains. Using AlphaFold2, we predicted the full SIX effector repertoire of Fol and show that SIX6 and SIX13 are also FOLD effectors, which we validated experimentally for SIX6. Based on structural prediction and comparisons, we show that FOLD effectors are present within three divisions of fungi and are expanded in pathogens and symbionts. Further structural comparisons demonstrate that Fol secretes effectors that adopt a limited number of structural folds during infection of tomato. This analysis also revealed a structural relationship between transcriptionally co-regulated effector pairs. We make use of the Avr1 structure to understand its recognition by the I receptor, which leads to disease resistance in tomato. This study represents an important advance in our understanding of Fol-tomato, and by extension plant-fungal interactions, which will assist the development of novel control and engineering strategies to combat plant pathogens.

plant biology↗

bioRxiv2020

The crystal structure of SnTox3 from the necrotrophic fungus Parastagonospora nodorum reveals a unique effector fold and insights into Kex2 protease processing of fungal effectors

O_LIPlant pathogens cause disease through secreted effector proteins, which act to modulate host physiology and promote infection. Typically, the sequences of effectors provide little functional information and further targeted experimentation is required. Here, we utilised a structure/function approach to study SnTox3, an effector from the necrotrophic fungal pathogen Parastagonospora nodorum, which causes cell death in wheat-lines carrying the sensitivity gene Snn3. C_LIO_LIWe developed a workflow for the production of SnTox3 in a heterologous host that enabled crystal structure determination. We show this approach can be successfully applied to effectors from other pathogenic fungi. Complementing this, an in-silico study uncovered the prevalence of an expanded subclass of effectors from fungi. C_LIO_LIThe {beta}-barrel fold of SnTox3 is a novel fold among fungal effectors. We demonstrate that SnTox3 is a pre-pro-protein and that the protease Kex2 removes the pro-domain. Our in-silico studies suggest that Kex2-processed pro-domain (designated here as K2PP) effectors are common in fungi, and we demonstrate this experimentally for effectors from Fusarium oxysporum f sp. lycopersici. C_LIO_LIWe propose that K2PP effectors are highly prevalent among fungal effectors. The identification and classification of K2PP effectors has broad implications for the approaches used to study their function in fungal virulence. C_LI

plant biology↗