Versatile effectors of phytopathogenic fungi target host immunity

Abstract

Phytopathogenic fungi secrete a large arsenal of effector molecules, including proteinaceous effectors, small RNAs, phytohormones and derivatives thereof. The pathogenicity of fungal pathogens is primarily determined by these effectors that are secreted into host cells to undermine innate immunity, as well as to facilitate the acquisition of nutrients for their in planta growth and proliferation. After conventional and non-conventional secretion, fungal effectors are translocated into different subcellular compartments of the host cells to interfere with various biological processes. In extracellular spaces, apoplastic effectors cope with physical and chemical barriers to break the first line of plant defenses. Intracellular effectors target essential immune components on the plasma membrane, in the cytosol, including cytosolic organelles, and in the nucleus to suppress host immunity and reprogram host physiology, favoring pathogen colonization. In this review, we comprehensively summarize the recent advances in fungal effector biology, with a focus on the versatile virulence functions of fungal effectors in promoting pathogen infection and colonization. A perspective of future research on fungal effector biology is also discussed.

Rab7/Retromer-based endolysosomal trafficking facilitates effector secretion and host invasion in rice blast

“…Phytopathogenic fungi secrete various types of effectors into the host tissue to suppress plant immunity, and promote colonization and disease [2, 3]. For the translocation of the effectors, M. oryzae possesses two distinct secretion pathways.…”

“…Despite the differences in lifestyles, a majority of these phytopathogens use a common strategy i.e. secretion of fungal effectors into the host to facilitate colonization [2, 3]. M. oryzae , the causal agent of the rice blast disease, seriously threatens rice production worldwide and has emerged as a top model to study host-fungus interaction [1, 4].…”

Action Mechanisms of Effectors in Plant-Pathogen Interaction

“…Although current research on effectors is quite prolific, and many effectors with clear mechanisms of action have been revealed, as the iceberg model proposed by Thordal-Christensen [ 35 ] suggests, there are more effectors, yet undiscovered, hiding under the iceberg in the large number of crosstalk signals between the interacting units. Based on existing research progress, this taxon of effectors is extremely broad in scope and exhibits surprising diversity [ 29 ]. Therefore, to discover commonalities among these molecular sequence diversities will be a major challenge.…”

“…The extraplasmic effectors dismantle the host physical and chemical barriers and break the first line of defense of the plant. The intracellular effectors target essential immune components in the plasma membrane, cytoplasm (including organelles) and nucleus, suppress host immunity, reprogram host physiology and favor pathogen colonization [ 29 ]. In the following sections, we synthesize the effectors that are well-researched under each mechanism for further classification and summary.…”

“…Ray et al [ 28 ] have provided a systematic review of the interaction between virus effectors and plants, so we do not repeat these details further here. Previously, Tariqjaveed et al [ 29 ] conducted a comprehensive review of fungal effectors based on their targets of action, and Pradhan et al [ 30 ] explored the double-edged role of fungal effectors in terms of different trophic types. While previous studies have focused more on discussing the spatial targets of effectors and the differences in effector deployment strategies among different pathogens, this review focuses on the role of effectors in different biological processes during infestation, highlighting recent progress made in the study of plant-pathogen interaction models and phytopathogenic bacterial, oomycete, and fungal effectors, and looking forward to the future challenges of effector research.…”