Necrotrophic pathogens are an important group of plant pathogenic fungi and bacteria notorious for their aggressiveness and broad host range. They actively kill plant cells to extract nutrients from dead tissue. Control of crop diseases caused by necrotrophic pathogens often relies on pesticide application because resistance to necrotrophic pathogens is usually controlled by multiple genes, making it difficult to breed for resistance. Presently, knowledge about, and understanding of the underlying molecular mechanisms for resistance to this type of pathogen is very limited. It is known to involve a process called autophagy in which specific cytoplasmic constituents are degraded, which in turn somehow prevents the invading necrotroph from inducing cell death. This project aims to elucidate the mechanism by which autophagy protects plants from necrotrophic pathogens.
At the focus of this project is a novel selective autophagy pathway mediated by the plant-specific ATI3 autophagy receptor, which is recruited to autophagosomes through interaction with ATG8. Genetic analyses suggest ATI3 plays a critical role in plant resistance to necrotrophs. ATI3 also interacts with UBAC2a and UBAC2b, homologs of a conserved ubiquitin-binding component of endoplasmic reticulum (ER)-associated degradation (ERAD). This project will test whether the ATI3 selective autophagy pathway plays an important role in plant immunity to necrotrophs by targeting deleterious ER constituents, thereby protecting against pathogen-induced, ER stress-mediated cell death. Specific objectives are to (1) confirm the critical role of ATI3 and UBAC2 in plant disease resistance through comprehensive genetic analysis; 2) determine whether the ATI3/UBAC2-mediated selective autophagy protects plant cells against pathogen-induced ER stress; and 3) analyze the role of the ER stress sensor IRE1 and the physical ATI3-UBAC2 interaction in the regulation of the ATI3 selective autophagy pathway. The goal of the project is the discovery of distinct pathways of selective autophagy associated with plant responses to specific plant biotic and abiotic stresses. Detailed knowledge on the role of autophagy in plant immune systems will lead to development of novel strategies for creating disease resistant crops. Autophagy and ERAD are also involved in many diseases in humans including cancers and, therefore, the knowledge from the project will have implications beyond the plant world. This project will provide a strong interdisciplinary training environment for graduate students. Some aspects of project will be incorporated into programs for training undergraduate students with hands-on experience in molecular biology techniques and for creative teaching in classrooms.
