Sheng Yang He Lab etched on to an Arabidopsis leaf using cryo-SEM focused ion beam

Plant diseases are one of the most important causes of crop loss globally, presenting a major obstacle in the sustained production of crops that are essential for basic human nutrition and health worldwide. Understanding how pathogens cause plant diseases therefore has far-reaching implications in agriculture and human health. Because of conceptual and mechanistic parallels in infectious diseases in plants and humans, elucidating the molecular bases of plant diseases also enriches the fundamental knowledge of infectious disease biology that is needed to develop innovative strategies to combat a variety of pathogens.

Research Interests

My lab is interested in elucidating how virulent bacterial pathogens cause diseases in susceptible plants. Using the Arabidopsis thaliana-Pseudomonas syringae system as a model and a variety of contemporary experimental approaches, we made significant progress toward this goal and contributed to the discovery of several key mechanisms underlying disease susceptibility and bacterial pathogenesis in plants.

Research Focus

In the past few years, we have concentrated our efforts on the study of the bacterial type III secretion system, the immune-suppressing functions of type III effectors, the immune function of plant stomata and the jasmonate hormone signaling cascade. Ultimately we would like to define all host cellular pathways a bacterial pathogen, like P. syringae, must subvert in order to cause disease in plants. A final proof of such an understanding would be reconstitution of disease susceptibility using a combination of host mutants that recapitulate disease development in the absence of bacterial infection, a task that has yet to be achieved in the study of any host-pathogen interaction in plants or humans.

New Research Initiatives

Despite significant progress, our current understanding of disease susceptibility and bacterial pathogenesis in plants remains largely one-dimensional, reflecting the heavy reliance of current studies on simplistic bilateral interactions of one pathogen and one host under largely static laboratory conditions. As a result, our current knowledge of disease susceptibility and bacterial pathogenesis does not reflect the multi-dimensional features of plant diseases that occur in nature. To break new grounds for the next phase of research on disease susceptibility and bacterial pathogenesis in plants, we initiated the following new research efforts in the past few years.

Disease Triangle
Environment and Disease: Understanding the molecular basis of the disease triangle dogma

A long-standing dogma in plant disease susceptibility states that disease outbreaks require not only the presence of a virulent pathogen and a susceptible host, but also a set of disease-favoring environmental conditions. The molecular basis of the “disease triangle” dogma is poorly understood, but is crucial for solving the mystery of many plant disease outbreaks in nature. Unlike static laboratory conditions, environmental conditions under which plants grow in nature are highly dynamic. Toward understanding the molecular basis of the disease triangle, we initiated major efforts aimed at elucidating how two of the most important environmental factors, temperature and humidity, exert their effects on the development of disease at the molecular level.

Plant Microbiome
Plant Microbiome and Disease: Development of a soil-based gnotobiotic system for plant research

Current studies of disease susceptibility and bacterial pathogenesis in plants have also paid little attention to the potential role of the microbiome that is indigenous to each plant. We believe that the next phase of research on disease susceptibility and bacterial pathogenesis must consider the microbiome as an integral component of a multi-dimensional interaction during disease. Unfortunately, the plant science community currently lacks a versatile microbe-free system that closely resembles plant growth conditions found in nature. In the past few years we initiated efforts to develop a soil-based gnotobiotic plant growth system (called “FlowPot”), which enables study of plant-microbe interactions in the presence or absence of the endogenous microbiome. With further optimization, we anticipate that the FlowPot gnotobiotic system may be broadly useful in the study of interplay between the microbiome and plant biology.

Modified COI1 receptor
Natural Defense Against Bacterial Type III Secretion

Because of the central role of the type III protein secretion apparatus in causing bacterial infections in plants and humans, there have been various efforts to inactivate this apparatus as a broadly applicable strategy for bacterial disease control. However, currently very little is known about the molecular interplay between the type III secretion apparatus and plant immune response. We have launched new efforts to determine the nature of host defenses against the type III secretion apparatus. If successful, we would develop innovative approaches to block this central virulence apparatus conserved in diverse bacterial pathogens.