Plants are in contact with diverse microbes blown by the wind, delivered via the water cycle and recruited to their roots and leaves from the soil. Many of these microbes are unable to start their life cycle in association with a living plant. Others are potential pathogens, potential symbionts, or harmless commensals. The ultimate outcome of plant-microbe interactions is tuned by host and microbe genotypes, and by the environmental context. While current research typically focuses on binary host-microbe interactions, essentially all land plants grow in intimate association with complex microbial communities. These attach to, and inhabit both the roots (rhizosphere) and above ground organs (phyllosphere) as epiphytes or endophytes. Plant-derived exudates and secreted secondary metabolites are implicated in encouraging specific microbial colonization including the well known interactions of legumes with nitrogen fixing bacteria. Host plants often rely on the associated microbiome for one or more critical nutrients, like fixed nitrogen. The plant, in turn, can provide fixed atmospheric carbon to some members of the microbiome, thus acting as a carbon sequestration niche.
Plant interactions with microbes are important in the context of plant health and global food security. Yield loses due to microbial pathogens and pests can be up to 30%, and much of this loss takes place after the fresh water input required to grow the crop in question. Thus, if we could better combat microbial infection of plants via rational deployment of the plant immune system, we could save significant amounts of water, and spare significant acreage from the plow.
We utilize genetics, genomics and molecular and cell biology tools to study the plant immune system, and, increasingly, how it intersects with assemblage of the plant microbiome (see ‘Major Achievements’). My lab currently focuses on these questions:
- How do plant intracellular NB-LRR innate immune receptors recognize pathogen virulence effectors and how are they activated?
- What is the structural and functional diversity of type III effectors from a single but widespread bacterial species, the host non-adapted pathogen Pseudomonas syringae (hereafter, Psy)?
- Do virulence effectors from two pathogens with very different life styles, P. syringae and an obligate biotrophic haustorial oomycete parasite, Hyaloperonospora arabidopsidis (hereafter, Hpa) converge onto a core set of host immune system targets?
- Can we expand our understanding of plant-microbe interactions to include the plant-associated microbiome and understand how the metagenome influences plant health and disease resistance?