Effectors of Plant Necrotrophic Fungi

Abstract

Plant diseases caused by necrotrophic fungal pathogens result in large economic losses in field crop production worldwide. Effectors are important players of plant-pathogen interaction and deployed by pathogens to facilitate plant colonization and nutrient acquisition. Compared to biotrophic and hemibiotrophic fungal pathogens, effector biology is poorly understood for necrotrophic fungal pathogens. Recent bioinformatics advances have accelerated the prediction and discovery of effectors from necrotrophic fungi, and their functional context is currently being clarified. In this review we examine effectors utilized by necrotrophic fungi and hemibiotrophic fungi in the latter stages of disease development, including plant cell death manipulation. We define "effectors" as secreted proteins and other molecules that affect plant physiology in ways that contribute to disease establishment and progression. Studying and understanding the mechanisms of necrotrophic effectors is critical for identifying avenues of genetic intervention that could lead to improved resistance to these pathogens in plants.

Keywords: defense suppression; effector; hypersensitive response; necrosis-inducing activity; necrotrophic fungi; programmed cell death; sRNA effectors.

FIGURE 1

Schematic representation of effector functions during plant-fungal necrotroph interactions. Effectors can be secreted into the apoplast or into plant cells from invasive hyphae, and can disrupt cell wall/membrane integrity, initiate programmed cell death (PCD), suppress PCD, alter hormone signaling, affect signaling cascades that use calcium ion fluxes, or suppress plant gene expression through small non-coding RNAs (sRNAs). Some of these processes have been shown to be light-dependent. Created with BioRender.com.