DISSECTING SIGNALING PATHWAYS IN PLANT IMMUNITY

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Dissecting signaling pathways in plant immunity Microbial diseases are a major threat to global crop production, resulting in annual crop yield losses between 10 to 16%. Billions of dollars are spent each year on pesticides to protect crops from pathogens. These chemicals are often damaging to the environment and may also lead to the evolution of pesticide-resistant pathogens. Thus, safe and sustainable pathogen control methods are critical to the success of modern agriculture. One successful approach is to breed crops with disease resistance (R) genes, which mostly encode nucleotide-binding domain and leucine-rich repeats (NLR) immune receptors that can perceive specific pathogens and trigger strong defense responses. Typical plant NLRs are further classified into Toll/interleukin-1 receptor (TIR) or coil-coiled (CC) type depending on their corresponding N-termini. Despite NLR-mediated resistance being highly effective, its molecular mechanism remains unclear. The long-term goal of my lab is to understand NLR-mediated immunity at the molecular level and use that knowledge to develop methods for sustainable crop protection. During the past decade, we have established several autoimmune models and successfully used them to discover many novel components that contribute to plant immunity. We showed that nucleocytoplasmic trafficking, transcriptional regulation, NLR dimerization/oligomerization, protein modifications and RNA processing all play important roles in NLR-mediated immunity. We also uncovered an NLR degradation pathway that regulates the homeostasis of NLRs. In this current NSERC Discovery program of research, we will build on these established autoimmune models and use next-generation sequencing, CRISPR/Cas9 gene editing and proteomics methods to identify key missing players of NLR-mediated immunity and elucidate how they function together to mount a proper defense upon pathogen attack. In the next five years, we will focus on the following two specific objectives: 1.Characterize TIR-type NLR (TNL) mediated immune signaling pathways activated through the helper NLRs, ADR1s and NRG1s; and 2.Dissect plant immune signaling pathways that are dependent or independent of the defense hormone salicylic acid. The proposed research will not only enrich our understanding of how plants defend against microbial pathogens and train the next-generation of highly qualified diverse scientists, but will also provide new insight for designing novel strategies to protect the crop plants without reliance on pesticides. In addition, as NLR receptors are also present in mammals, our proposed studies on plant NLRs may shed light on how their animal counterparts function and could thus have potential health benefits.