Monday June 3, 2019 // Regulation of receptor kinase-mediated signaling during plant immunity and beyond
Cyril Zipfel // Institute of Plant and Microbial Biology, Zürich-Basel Plant Science Center University of Zürich, Switzerland
Plants genomes encode hundreds of cell surface-localized receptor kinases that control almost all aspects of plant life, ranging from reproduction, growth to responses to the external environment. Using receptor kinases that function as immune receptors by perceiving microbial elicitors, we are studying the molecular basis of plant immunity, but also more generally how plant receptor kinases work at the mechanistic level. Using the leucine-rich repeat receptor kinases FLS2 and EFR (which perceive bacterial flagellin and EF-Tu, respectively) as model systems, we are investigating how plant receptor kinases function as part of multimeric protein complexes at the plasma membrane – often in complex with other receptor kinases, which act as regulatory proteins. I will present our recent work that uncovered the importance of these regulatory receptor kinases and receptor kinase-associated proteins in controlling the assembly and activity of functional heteromeric receptor complexes.
Special Biology Seminar: Biological Sciences room 3110, Monday June 3, 11:30 - 12:30
April 18, 2019 // What’s Stomata With You? Investigating the Role of a Protein Kinase Family in Stomatal Defense
Kristen Siegel, MSc Candidate, Dept Biology, Queen's University, Monaghan Lab
Stomata are microscopic pores found in leaf epidermal tissue that facilitate gas exchange between a plant and its environment during photosynthesis. Each pore is bordered with two specialized guard cells, which can modulate their turgidity to cause stomatal opening or closure. Photosynthetically favourable conditions, such as high levels of blue light, induce stomatal opening through guard cell water uptake. However, these openings are also commonly seized as a point of entry for plant microbial pathogens. Upon pathogen detection, plasma membrane-localized receptors will initiate intracellular signalling cascades, and ultimately cause stomatal closure though water efflux and guard cell deflation. This process, known as stomatal defense, contributes to a broad-spectrum immune response which is sufficient to defend against most pathogens. In a proteomics-based screen for regulators of immunity in Arabidopsis thaliana, we identified components of stomatal defense as well as several proteins with unknown function. Of particular interest was a novel protein belonging to a small family of mitogen-activated protein kinases involved in blue-light induced stomatal opening. This work investigates the putative role of this family in stomatal defense and immune signalling.
April 11, 2019 // Guarded and Targeted: Investigating the role of MACPF domain proteins in plant immunity
Irina Sementchoukova, MSc candidate, Monaghan Lab, Dept Biology, Queen's
Pseudomonas syringae is a bacterial pathogen that causes disease in a broad range of plant species. As a part of its infection strategy, P. syringae releases virulence factors called effectors into plant cells to disarm host defenses. In response to effector sabotage, plants evolved intracellular NUCLEOTIDE BINDING AND LEUCINE RICH REPEAT RECEPTORS (NLRs) that ‘guard’ the integrity of critical immune signalling components prone to be effector targets. When no damage is detected, NLRs remain in the ‘OFF’ state, and only turn ‘ON’ when perturbations are detected in the guarded protein. Activated NLRs typically result in a form of programmed cell death at the site of infection that protects surrounding uninfected tissues. MEMBRANE ATTACK COMPLEX/PERFORIN (MACPF) proteins are well known agents of defense in the mammalian immune system, though the molecular function of this protein family in plants has not been established. The model plant Arabidopsis thaliana encodes four MACPF domain proteins, and genetic evidence suggests that at least two of these proteins are involved in the plant immune response. Interestingly, loss-of-function mutations in these loci result in hyperactive immune signaling and cell death, reminiscent of dysregulated NLR activation. My project has thus been focused on determining if MACPF proteins may be effector targets guarded by plant NLRs.
Dr. Peter Roy, Dept Molecular Genetics, University of Toronto
The Roy Lab at the University of Toronto has spent over a decade exploring the utility of C. elegans in drug development. In this seminar, Prof. Roy will introduce the nematode C. elegans as a tool for medium-throughput small-molecule screens. He will then describe three vignettes that illustrate the power and peril of using C. elegans to develop small molecules that have utility beyond the bench.
Dr. Dawn Hall, Office of the Chief Information Officer, Treasury Board of Canada Secretariat, Government of Canada
When I obtained a PhD in Biology in 2007, I never would have predicted what the next 10+ years of my career would bring. This talk will begin with a retrospective look at my time as a PhD student and post-doc, followed by a description of the career experiences that have followed: from science communication and exhibit content development at the Ontario Science Centre, to exhibit interpretation for the renewal of the Canada Science and Technology Museum, to my current role as an analyst/advisor with the Government of Canada. Throughout, I will discuss the decisions that I made, and how the skills that were developed during my PhD and post-doc were applied in the jobs that have followed. I will also share lessons learned and perspectives from the career journey.
Dr. Louise Winn, Dept of Biomedical and Molecular Sciences, Queen's University
Drugs and environmental chemicals can harm the developing fetus by causing not only the commonly appreciated structural defects such as cleft lip, but also biochemical and functional abnormalities related to alterations in membranes as well as enzymes and other proteins. These compounds can also disrupt normal metabolic and endocrine signalling via epigenetic modifications, including DNA methylation, histone modifications, and/or RNA-mediated silencing of genes through miRNA, resulting in negative health outcomes later-in-life.My research program aims to investigate mechanisms of in utero initiated developmental toxicity employing a combination of expertise in biochemical and morphological assessment of chemical toxicity, and molecular toxicological approaches. Our goal is to answer fundamental mechanistic questions about the biological effects of in utero exposures to drugs and environmental chemicals to inform exposure monitoring practices, policy and human health assessments.
Feb 28, 2019 // Exploration of sustainable Arctic fisheries: microbiomes for bioprospecting and fish health assessments
Erin Hamilton, M. Sc. Candidate
The Towards a Sustainable Fishery for Nunavummiut (TSFN) Project is partnered with the Nunavut community of Gjoa Haven. We are using genomic and microbial analyses to inform strategies to retain genetically-diverse and healthy fish stocks for Inuit communities. In this region, Arctic char (Salvelinus alpinus) and whitefish (Coregonus spp.) can be anadromous, migrating annually from the ocean to freshwater lakes and rivers in order to escape sub-zero temperatures. The fish and their associated microbiomes must adapt accordingly to their changing environment. Analysis of fish microbial community compositions has shown that skin bacterial communities are statistically different when sampled from freshwater or saline water sites, but appear to maintain a core community, with Proteobacteria, Firmicutes, and Cyanobacteria presenting as major phyla. Given these findings, microbial assemblages could be used as a proxy for fish health. In addition, there is bioprospecting potential for microbial taxa that could provide advantages for fish in aquaculture.
Friday, Feb 22, 11:30-12:30 // Temporal changes of Arabidopsis plasma membrane proteome during cold- and de-acclimation
Dr. Matsuo Uemura, Faculty of Agriculture, Iwate University, Morioka, Japan
Freezing stress is one of the most important limiting factors of plant survival. Plants have developed a freezing adaptation mechanism upon sensing low temperatures (cold-acclimation). Compositional changes in the plasma membrane, one of the initial sites of freezing injury, is prerequisite of achieving cold acclimation and have been investigated in several plant species. However, the cold dehardening process at elevated temperatures (de-acclimation) has not yet been fully characterized. Here we conducted shotgun proteomics with label-free semiquantification on plasma membrane fractions of Arabidopsis leaves during cold acclimation and de-acclimation. A list of 873 proteins with significantly changed proteins in response to the two processes was obtained. Although the cold-acclimation-responsive proteins were globally returned to non-acclimated levels by de-acclimation, several representative cold-acclimation-responsive proteins tended to remain at higher abundance during de-acclimation process. Our results suggest that plants deharden right after cold acclimation to restart growth and development but some protein changes of the plasma membrane may be maintained to cope with the threat of sudden freezing during deacclimation process.
Dr. Mark Belmont, University of Manitoba
This seminar will provide insights into the utility of next generation, RNAi-based molecular fungicides and their applicability to control crop pathogens. Sclerotina sclerotiorum, the causal agent of white mold, infects over 450 species of plants worldwide. This fungal phytopathogen has become a major threat to crops including canola which contributes $27 billion to the Canadian economy. Sclerotinia is a persistent problem for canola growers that has traditionally been managed using broad-spectrum fungicides. However, current fungicide strategies have proven to be ineffective. Thus, there is an immediate need to manage Sclerotinia using novel species-specific control methods. Our strategy exploits the inherent cellular defense process known as RNA interference (RNAi). Upon encountering a double stranded RNA (dsRNA) molecule, the cell processes the dsRNA specifically targeting transcripts with sequence homology. Sclerotinia-specific target genes were identified using bioinformatics. RNAi knockdown was confirmed using qRT-PCR on RNA isolated from fungal cultures. Transgenic plants over-expressing the dsRNA showed a profound and prolonged tolerance to Sclerotinia.
Dr. Adam Mott, Dept Biology, Univ Toronto, Scarborough Campus
To thrive, plants must be able to quickly recognize and respond to changing environmental conditions and pathogen attack. The perception of many signals is accomplished through the collective action of members of the leucine-rich repeat receptor kinase (LRR-RK) family, of which there are 225 in Arabidopsis. Upon detection of an extracellular signal, these receptors physically interact to form signaling-competent structures able to integrate complex signals to guide plant defence and growth. Using a high-throughput interaction screen we determined the physical interactions between 200 of the LRR-RLKs from Arabidopsis. Using network analysis and community detection we have detected distinct, but interconnected, subnetworks that show evidence of specialized biological activity and demonstrated novel function for several previous unstudied receptors. In addition, we show that the overall network structure is critical for proper signaling responses, and disruptions can have unexpected consequences at a distance.