Exploring folds, evolution and host interactions: understanding effector structure/function in disease and immunity

Abstract

Summary Over the past decade, tremendous progress has been made in plant pathology, broadening our understanding of how pathogens colonize their hosts. To manipulate host cell physiology and subvert plant immune responses, pathogens secrete an array of effector proteins. A co‐evolutionary arms‐race drives the pathogen to constantly reinvent its effector repertoire to undermine plant immunity. In turn, hosts develop novel immune receptors to maintain effector recognition and mount defences. Understanding how effectors promote disease and how they are perceived by the plant's defence network persist as major subjects in the study of plant–pathogen interactions. Here, we focus on recent advances (over roughly the last two years) in understanding structure/function relationships in effectors from bacteria and filamentous plant pathogens. Structure/function studies of bacterial effectors frequently uncover diverse catalytic activities, while structure‐informed similarity searches have enabled cataloguing of filamentous pathogen effectors. We also suggest how such advances have informed the study of plant–pathogen interactions.

Perception of structurally distinct effectors by the integrated WRKY domain of a plant immune receptor

“…Diffraction data was collected at Diamond Light Source, i03 beamline, under proposal mx18565. The data were scaled and merged by Aimless in the CCP4i2 software package (2). The AvrRps4 C /RRS1 WRKY complex structure was solved by molecular replacement using PHASER (3) with the structures of AvrRps4 C (PDB ID: 4B6X) and PopP2/RRS1 WRKY (PDB ID: 5W3X) as search models.…”

“…Plants co-evolve with their pathogens, resulting in extensive genetic variation in host immune receptor and pathogen virulence factor (effector) repertoires (1). To enable host colonization, pathogenic microbes deliver effector proteins into host cells that suppress host immune responses and elevate host susceptibility by manipulating host physiology (2, 3). Plants have evolved surveillance mechanisms to detect and then activate defenses that combat pathogens, and detect host-translocated effectors via nucleotide-binding leucine-rich repeat receptors (NLRs) (4).…”

The Phytophthora effector Avh241 interacts with host NDR1‐like proteins to manipulate plant immunity

“…Sequence analyses revealed that Avh241 contains two conserved WY motifs, which have been identified in many RxLR effectors (Yu et al, 2012). Although the sequence similarity of these effectors is low, they display a conserved fold buried within the core of the helical bundle (Win et al, 2012; Mukhi et al, 2020). Recently, the crystal structure of Avh240 revealed a duplicated WY domain with a novel assembly model (Guo et al, 2019).…”

Comparative secretomics identifies conserved WAxR motif-containing effectors in rust fungi that suppress cell death in plants

“…The successful loosening of the cell wall further causes the transfer of various apoplastic, cytoplasmic effectors as well as virulence determinants that suppress the immunity of the host in numerous ways. Several novel mechanisms have been utilized by pathogens that have been highlighted by recent studies, such as suppressing RNA interference, targeting various cellular organelles of host plants, and maintaining conserved fold in the novel effectors to perform a conserved molecular function(de Guillen et al, 2019; Jaswal et al, 2020; Mukhi et al, 2020; Xu et al, 2019; Yin et al, 2019).…”