Fungal effectors and plant susceptibility

Plants can be colonized by fungi that have adopted highly diverse lifestyles, ranging from symbiotic to necrotrophic. Colonization is governed in all systems by hundreds of secreted fungal effector molecules. These effectors suppress plant defense responses and modulate plant physiology to accommodate fungal invaders and provide them with nutrients. Fungal effectors either function in the interaction zone between the fungal hyphae and host or are transferred to plant cells. This review describes the effector repertoires of 84 plant-colonizing fungi. We focus on the mechanisms that allow these fungal effectors to promote virulence or compatibility, discuss common plant nodes that are targeted by effectors, and provide recent insights into effector evolution. In addition, we address the issue of effector uptake in plant cells and highlight open questions and future challenges.