Howard Teresinki PhD Candidate, Snedden Lab, Queen's University Identification and characterization of novel targets for a subfamily of Arabidopsis calmodulin-like (CML) proteins
Calcium is a ubiquitous second messenger in signal transduction pathways of all eukaryotic cells. In plants, calcium signalling plays critical roles in a variety of developmental processes as well as during cellular responses to abiotic and biotic stress. The evolutionarily-conserved calcium sensor, Calmodulin (CaM), responds to calcium signals and, through protein-protein interactions in cells, facilitates downstream responses. Plants possess an additional and unique family of “calmodulin-like” (CML) calcium sensors which, in Arabidopsis thaliana, contains 50 members. Despite this expanded complexity, few of the binding partners and/or in vivo functions of CMLs are known. Here I present data from my PhD thesis demonstrating that CaM and a subfamily of biochemically unusual CMLs are capable of interacting with specialized structural domains from among three distinct and unrelated protein families in Arabidopsis. I utilised a combination of genetic, biochemical, and biophysical approaches to explore the physical properties and physiological roles of CML interactions with these putative targets. Collectively, my data suggests novel functions for plant CMLs in gene regulation and cytoskeletal activity.
Dr. Arinjay Banerjee Laboratory for Zoonotic Viruses and Comparative Immunology, University of Saskatchewan Past, present and future of SARS-CoV-2
Dr. Arinjay Banerjee is a postdoctoral researcher in Dr. Karen Mossman’s laboratory at McMaster University. Over the last 6 years, he has studied emerging zoonotic viruses, such as coronaviruses that spill over from wildlife species (eg. bats) to infect humans and cause severe disease. More recently, Dr. Banerjee has been investigating SARS-CoV-2 and its interaction with the human immune system. In this talk, he will discuss his current research on SARS-CoV-2 and work that his team shall undertake at the Vaccine and Infectious Disease Organization to investigate emerging zoonotic viruses and develop countermeasures.
Dr. David Ng AMBL, Michael Smith Laboratories, University of British Columbia The Phylo Trading Card Game: A crowdsourced game-based learning approach to biodiversity education
The Phylo Trading Card game is an exercise in crowdsourced game design with the explicit intent of introducing biodiversity and other STEM concepts to its players. The Phylo game is a competitive and interactive way for participants to engage with species and ecosystems. This seminar will talk about the origins and progression of the project as a tool for STEM related game-based learning. The talk will also briefly mention a pilot study that revolved around human perceptions of wildlife and identifying whether such perceptions may be altered by using the game as a potential tool. Utilizing an in-lab study design, this research identified the impact of this novel educational approach and compared it to more traditional teaching methods across criteria including ecological perceptions, knowledge, positive and negative affect, and species recall.
Ryan Kilburn PhD Candidate, Plaxton & Snedden Labs Investigations into the multifaceted functions of Ricinus communis calcium-dependent protein kinase-1 (RcCDPK1)
As the global population grows and demands on agricultural land rise, there is a need to increase crop yields. Castor (Ricinus communis) oil seeds (COS) have become an important model for oil seed metabolic engineering due to their massive accumulation of oil at maturity relative to commercially important oil seeds such as canola. In developing COS, a unique ‘bacterial-type’ phosphoenolpyruvate carboxylase (PEPC) isozyme is highly expressed as a regulatory and catalytic subunit of a novel Class-2 PEPC complex. Class-2 PEPC’s unique kinetic and regulatory properties, and dynamic subcellular targeting to the mitochondrial surface, support the hypothesis that it facilitates rapid refixation of respiratory CO2 while sustaining a large anaplerotic flux to replenish TCA cycle C-skeletons withdrawn in support of storage oil and protein biosynthesis in developing COS. R. communis Ca2+-dependent protein kinase-1 (RcCDPK1) catalyzes in vivo inhibitory phosphorylation of bacterial-type PEPC (BTPC) at Ser451 in developing COS (Ying et al. 2017 Plant Physiol.). This research aims to address how autophosphorylation influences RcCDPK1’s ability to transphosphorylate BTPC at Ser451. Interestingly, RcCPDK1 exhibits high sequence similarity (83%) to its closest ortholog from the model plant Arabidopsis thaliana, AtCPK4, which also catalyzes Ca2+-dependent phosphorylation of COS BTPC at Ser451 in vitro. AtCPK4 also appears to regulate signal transduction of the stress hormone abscisic acid (ABA) by phosphorylating an important ABA-responsive transcription factor (AtABF4), raising questions about further overlap between substrates of these two CDPK orthologs, and ultimately whether RcCDPK1 might also function in castor ABA signaling. Using a mix of biochemistry and genetic approaches with a focus on enzyme kinetics and functional genomics, this project aims to unravel understudied aspects of autophosphorylation in CDPKs, as well as to determine possible links between the control of central carbon metabolism and ABA signaling.
Dr. Gian Luca Negri Genome Sciences Centre, BC Cancer Research Centre Unraveling biological complexity through proteomics: applications and challenges
Mass spectrometry has become a commonly used technique to study complex biological processes. Although several strategies now make it possible to measure the proteome with increasing depth and accuracy, several challenges remain. In this talk, I introduce the general workflow of mass spectrometry-based proteomics with a focusing on experimental design, technical and computational considerations. I use examples from flies to humans and highlight the intricacy of integrating mass spectrometry with other high-throughput data.
Dr. Ian Chin-Sang Department of Biology, Queen's University Using a tiny worm to help solve a big problem like cancer
Cancer often results when normal signal transduction pathways go awry due to the abnormal regulation or function of the genes in these pathways. A major oncogenic pathway is the Insulin and Insulin Growth Factor Signaling (IIS) pathway. The insulin and insulin-like growth factor signaling (IIS) pathways have multiple functions in development, metabolism, reproduction, lifespan and behaviour. A very important negative regulator of this pathway is the tumour suppressor PTEN. In a remarkable parallel, loss of the C. elegans PTEN orthologue (DAF-18) causes cells to divide when they should remain quiescent. Furthermore, the human PTEN can functionally replace worm DAF-18. When C. elegans hatch in the absence of food it shuts down its development until food is available in a process called L1 arrest. Normally during L1 arrest the Q neuroblasts remain quiescent, however, in daf-18 mutants the Q neuroblasts proliferate, migrate and differentiate. We have used genetic suppressor screens and pharmacological tests to identify novel branches and regulators of the C. elegans IIS. We also systematically overexpressed each of the 40 Insulin-like peptides in C. elegans to provide roles for each. We showed that some insulin peptides can activate the receptor while some inhibit the receptor, while others have mixed function (agonists or antagonists) depending on the developmental process. We have used this data to determine what makes an insulin-like peptide an activator or inhibitor of the DAF-2 insulin-like receptor. Our research using C. elegans has identified novel regulators of IIS and will help in the clinical setting by providing valuable information on human PTEN variants of unknown significance. The inhibitory insulin-like peptides will provide mechanistic insight for therapies to treat hyperinsulinemia related diseases.
Dr. Elizabeth Rideout Department of Cellular and Physiological Sciences, UBC Molecular mechanisms of sex-specific body size plasticity in Drosophila
The ability to adjust body size in response to nutrients differs between the sexes in most species, including mammals. Yet the molecular mechanisms underlying this sex-specific body size plasticity remain unknown. In our work, we used the fruit fly, Drosophila melanogaster, to reveal the molecular mechanisms underlying the sex difference in body size plasticity. Normally, the magnitude of the body size increase in response to a nutrient-rich diet is higher in female flies. We recently discovered that a nutrient-rich diet augments body size in females and not males because of a female-biased increase in activity of the conserved insulin signaling pathway. We further identified the factors that allow females, and not males, to augment insulin signaling in response to nutrients. This knowledge provides important evidence of how the insulin pathway can be regulated differently in each sex, and provides clues into why there are sex differences in so many phenotypes (e.g. lifespan) and diseases (e.g. type 2 diabetes) associated with the insulin pathway.
Dr. Sonali Roy Noble Research Institute Regulation of Nitrogen Acquisition by Peptide Hormones
The root system of a plant performs vital functions including resource uptake when nutrient availability in soil is non-homogenous; while also providing a surface for interactions with beneficial microbes. Legume roots tolerate deficiency of the macronutrient Nitrogen by not only enhancing its direct uptake but also by establishing a unique symbiotic relationship with soil bacteria called rhizobia. Here I present findings that put genome-encoded small secreted peptides or ‘peptide hormones’ at the center-stage of N-acquisition in legumes. Our findings suggest that peptides likely provide a cheap, environmentally-friendly, non-GMO route to address current challenges of plant growth in nutrient-deprived soils.
Checkmate: You've been ubiquitinated! Investigating ubiquitin-mediated turnover of BIK1, a key plant immune signalling kinase
Plants are susceptible to infection from bacterial, fungal, and viral diseases; although they cannot run away, they are far from defenseless! Plants have complex immune systems that are responsible for the detection of pathogens and initiating signal transmission in order to respond to and fight off infections. BOTRYTIS INDUCED KINASE 1 (BIK1) is a key regulator of immune signaling that is required for protection against multiple types of pathogens. BIK1 is activated through phosphorylation by plasma-membrane receptor kinases and in turn phosphorylates and activates other downstream proteins. To prevent overactive immune responses, accumulation of BIK1 is tightly regulated through ubiquitination by PLANT U-BOX 25 and subsequent degradation by the proteasome. This thesis investigates the functional importance of ubiquitination on BIK1 and how ubiquitination impacts BIK1 turnover. We identified nine BIK1 ubiquitination sites using highly sensitive mass spectrometry. Higher order ubiquitin-ablative mutants were generated to determine which terminal residues are important for proteasomal turnover. We verified that BIK1 ubiquitin-ablative mutants were catalytically active and appropriately localized to the plasma membrane and nucleus when transiently expressed in tobacco. Using a semi-in vivo approach, I demonstrate that ablating all nine of these BIK1 ubiquitination sites slows the rate of degradation and therefore may be important for regulating BIK1 levels in plants. Genetic analyses were explored using mutated BIK1 variants in a bik1 knockout or WT background but yielded inconclusive data. This work contributes to the growing body of literature on post-translational modification by ubiquitination and highlights that, unlike certain post-translational modifications which are highly residue specific (ie phosphorylation), ubiquitination substrate specificity is likely less critical at the residue level.
Dr. Peter Mergaert Centre National de la Recherche Scientifique Role of antimicrobial peptides and the ROS-producing enzyme Duox in insect gut symbiosis
Most animals harbor a gut microbiota that consists of potentially pathogenic, commensal and mutualistic microorganisms. In insects, antimicrobial peptides (AMPs) and the reactive oxygen species (ROS)-producing enzyme “Dual oxidase” (Duox) are the central regulators of gut mucosal immunity. They antagonize pathogenic bacteria and maintain gut homeostasis. However, the non-specific harmful activity of AMPs and ROS on microorganisms raises the question about the role of AMPs and Duox in the maintenance of mutualistic gut symbionts. In my seminar, I will highlight how AMPs and Duox control the establishment of a specific gut symbiosis in the bean bug Riptortus pedestris, which harbors in a symbiotic compartment of the midgut the mutualistic bacterium Burkholderia insecticola. We have demonstrated that symbiosis-specific as well as immunity-specific AMPs are produced massively during B. insecticola infection of the gut and that resistance to these AMPs is crucial for the capacity of the bacterium to colonize the gut. On the other hand, and contrarily to our initial expectation, we found that Duox-dependent ROS did not directly contribute to epithelial immunity in the midgut in response to B. insecticola or to pathogenic bacteria. Instead, we demonstrated that Duox is essential for symbiosis and the colonization of the gut by the aerobic B. insecticola by mediating the formation of a respiratory network enveloping the gut.