The structural landscape and diversity ofPyricularia oryzaeMAX effectors revisited

Abstract

Plant pathogenic fungi secrete a wide variety of small proteins, named effectors.MagnaportheAVRs and ToxB-like (MAX) effectors constitute a superfamily of secreted proteins widely distributed inPyricularia (syn. Magnaporthe) oryzae, a devastating fungus responsible for blast disease in cereals such as rice. In spite of high evolutionary sequence divergence, MAX effectors share a common fold characterized by a ß-sandwich core often stabilized by a conserved disulfide bond. In this study, we investigated the structural landscape and diversity within this effector family based on a previous phylogenetic analysis ofP. oryzaeprotein sequences that identified 94 ortholog groups (OG) of putative MAX effectors. Combining protein structure modeling approaches and experimental structure determination, we validated the prediction of the conserved MAX core domain for 77 OG clusters. Four novel MAX effector structures determined by NMR were in remarkably good agreement with AlphaFold2 (AF) predictions. Based on the comparison of the AF-generated 3D models we propose an updated classification of the MAX effectors superfamily in 20 structural groups that highlight variation observed in the canonical MAX fold, disulfide bond patterns and decorating secondary structures in N- and C-terminal extensions. About one-third of the MAX family members remain single, showing no obvious structural relationship with other MAX effectors. Analysis of the surface properties of the AF MAX models also highlights the very high variability remaining within the MAX family when examined at the structural level, probably reflecting the wide diversity of their virulence functions and host targets.Author summaryMAX effectors are a family of virulence proteins from the plant pathogenic fungusPyricularia (syn. Magnaporthe) oryzaethat share a similar 3D structure despite very low amino-acid sequence identity. Characterizing the function and evolution of these proteins requires a detailed understanding of their structural diversity. We used a combination of experimental structure determination and structural modeling to characterize in detail the MAX effector repertoire ofP. oryzae. A prediction pipeline based on similarity searches and structural modeling using the AlphaFold2 (AF) software were used to predict MAX effectors in a collection of 120P. oryzaegenomes. We then compared AF models with experimentally validated NMR structures. The resulting models and experimental structures revealed that the preserved MAX core coexists with extensive structural variability in terms of structured N- or C-terminal extensions. For each of the AF models, we also analyzed the surfaces of the canonical fold that may be involved in protein-protein interactions. This work constitutes a major step in mapping the functional network of MAX effectors through their structure by identifying possible recognition sites that may help focusing studies of their putative targets in infected plant hosts.

Pyricularia oryzae: Lab star and field scourge

“…MAX effectors are massively and specifically expressed during early biotrophy (de Guillen et al., 2015 ; Le Naour‐Vernet et al., 2023 ; Yan et al., 2023 ). They include many AVR proteins recognized by intracellular NLR immune receptors (Lahfa et al., 2023 ). Additional structural families of P. oryzae effectors have been identified by genome‐wide modelling of protein structures (Derbyshire & Raffaele, 2023 ; Seong & Krasileva, 2021 ; Seong & Krasileva, 2023 ).…”

Resistance Analysis of Padi Gogo Merah (Oryza Nivara L) Against Blast Disease

“…Gene annotation investigation successfully identified 58 to 78 MAX effector genes per genome in a set of 120 isolates representing seven host-associated lineages leading to restriction of early biotrophic infection and strongly influenced by the host plant . NMR observation shown that MAX effectors superfamily in 20 structural groups that vary in the canonical MAX fold, disulfide bond patterns, and additional secondary structures in N-and C-terminal extensions which potentially effecting the wide diversity of their virulence functions and host targets (Cadiou, et al, 2023;Lahfa et al, 2023).…”