Membrane Biogenesis and Protein Targeting in Haustorium-invaded Plant Cells

University Of Maryland, College Park, College Park MD

Investigators

Abstract

Plants are the ultimate food source for non-photosynthetic organisms. Many pathogenic fungi and oomycetes develop a feeding organ named the haustorium to extract nutrients from host plants. Such pathogens cause widespread and/or devastating crop diseases such as wheat powdery mildew and rust, potato late blight and sudden oak death, resulting in huge crop losses and tree damages worldwide. In recent years, much has been learnt about the molecular mechanisms concerning plant immunity. However, how defense responses are executed at host-pathogen interfaces is poorly understood. Interactions between the model plant Arabidopsis (epidermal cell)and Powdery mildew (haustorium) provides a convenient single-cell system for addressing this challenging question. The project utilizes an Arabidopsis resistance protein that is specifically targeted to the plant-fungal interface as a unique tool to investigate the formation of the interfacial membrane, how that formation is coupled to immune signaling and protein trafficking to enable defense execution at specific subcellular sites. New information from this project should help elucidate the fundamental cell biology principles governing formation of and activities at host-microbe interfacial membranes, and yield new insight into novel intervention strategies to control plant diseases caused by haustorium-forming pathogens. The outcome of the host-pathogen interaction is determined at the extra-haustorial membrane (EHM), the host-pathogen interface. However, both the origin and biogenesis of the EHM and the molecular host-pathogen interactions at this interface are largely unknown. The long-term goal of this project is to understand the biogenesis of the EHM and its role in host defense and fungal development. These investigators have shown that (i) a host resistance (R) protein named RPW8 from Arabidopsis is specifically targeted to the EHM where it activates haustorium-targeted defenses via an unknown mechanism; and that (ii) RPW8 contains two putative basic residue-enriched motifs essential for EHM-targeting. Therefore, RPW8 can be used as a unique tool to understand the host defense at the EHM, the origin and biogenesis of the EHM, and the EHM-oriented protein trafficking in the invaded host cell during haustorial development. Specifically, there are three major aims for this project. Aim 1 addresses how hydrogen peroxide is produced and accumulated in the host-pathogen interface during RPW8-mediated and basal resistance against haustorium-forming pathogens. Aim 2 is focused on characterization of a special protein (SNARE) complex that is engaged in the EHM-oriented vesicle trafficking. Aim 3 investigates EHM biogenesis and its role in host defense and fungal pathogenesis. A combinatory forward and reverse genetics approach, aided by chemical genetic assays and state-of-the-art confocal imaging will be employed to achieve the above three specific objectives. Novel and important knowledge from this project will significantly advance our current understanding of the cell biology and molecular interaction between plants and haustorium-forming pathogens, which should help design new strategies to control plant diseases caused by such pathogens in the future. The investigators will also continue to produce short videos of their work that can be disseminated and used for teaching.