Research in the Xu laboratory focuses on plant and microalgal lipid metabolism. By applying state-of-the-art approaches in genetics, biochemistry, cellular biology, synthetic biology and biotechnology, we aim to address both fundamental and applied questions in the field. The major research objectives in our research group are to improve our understanding of the mechanisms underlying acyl lipid assembly (e.g. triacylglycerols/oils, galactolipids/photosynthetic membrane lipids, phospholipids/membrane lipids) in photosynthetic organisms and to design lipid biosynthetic pathways to improve agriculture production and produce value-added oils for food, feed, fuel, and materials applications.Learn More
Research Area: Biotechnology
Our work spans three research themes:
1) DNA metasystematics: We gather biodiversity data through the analysis of marker genes from bulk samples (water, soil, and sediments). We pioneered this technique for benthic macroinvertebrates, used widely as bioindicators of aquatic ecosystems.
2) Biodiversity transcriptomics: We develop comparative transcritpome-based approaches for non-model organisms to gain insights on evolution of transcriptomes and understand molecular responses at ecological scale.
3) Bioinformatic approaches for biodiversity genomics data: We develop and test taxonomic assignment approaches for many taxonomic groups and marker genes, and develop tools to enhance analysis of metabarcoding and biodiversity genomic data through machine-learning methods and refined analysis.
Research in my laboratory is focused on the architecture and assembly of the cell surfaces of pathogenic bacteria. Current areas of emphasis are:
1) Structure and function of multi-enzyme complexes required for the export of capsular polysaccharides through the periplasm and across the outer membrane of Gram-negative bacteria.
2) Structural basis for substrate recognition by ABC transporters involved in the export of bacterial cell-surface polysaccharides.
3) Structure and function studies of prokaryotic glycosyltransferase enzymes.
4) Mechanisms that couple glycan biosynthesis and chain extension to transport pathways.
My research group focuses on the diagnosis, prognosis and treatment of Lyme disease. I focus on different topics within this research theme, including: 1) the various forms that Borrelia (Lyme bacteria) can adopt and their corresponding role in the expression of the disease; 2) the effects of people and bacteria genetics in the expression of of the disease; 3) the development of new diagnostic tools; and, 4) the interactions that people diagnosed with Lyme disease have with the medical system.Learn More
My background is in molecular and cell biology of lipid metabolism. Currently, my students and I work on the regulation of membrane phospholipids, fatty acids, and methyl-group donors. More specifically, we look at regulation of genes involved in choline transport and phospholipid metabolism; nutrient transporters and kinetics of membrane transport; molecular and cell biology of lipids; the effect of nutrients on protein synthesis and gene expression; and, nutritional genomics (nutrigenomics) of risk factors for cardiovascular disease and insulin resistance.Learn More
The ultimate goal of my research is to understand viruses and viral diseases for the betterment of agriculture. Our research involves a number of important viruses that infect plants, which include Grapevine rupestris stem pitting-associated virus (GRSPaV), a ubiquitous and important pathogen of grapes worldwide. Current research directions include: Processing and subcellular localization of polyproteins; structure and cellular localization of viral replication complexes; evolution and bio-informatics of grapevine viruses; development of virus-induced gene-silencing vectors ; and, development and application of technologies for the diagnosis of grapevine viruses.Learn More
My research group investigates biotic and abiotic stress on plants at the cellular and sub-cellular biochemical and molecular levels. The objective is to identify what changes occur in plant cells upon exposure to stress and which of these changes aid the plant to increase its tolerance to the stress.A major focus currently is the investigation of freezing stress tolerance in grapevines. Winters in Ontario can cause substantial damage to the cultivated grapes used in the Wine Industry, whereas wild grapes have no problems. We try to find out what the molecular basis is for this phenomenon. The ultimate goal is to use this knowledge to improve freezing and drought stress tolerance in the cultivated grapes.Learn More
A key focus of the group is on the protein degradation machinery that helps to maintain proper level of proteins (protein homeostasis) in Mycobacterium tuberculosis, the causative agent of TB, the world's single largest infectious killer that is annually responsible for 1.5 million deaths. The questions we aim to answer are:
1) What is the assembly mechanism of the M. tuberculosis proteasome core particle and its regulatory particles?
2) What is the role of allostery and long-range interactions in the machinery that tags substrates for proteasomal degradation?
3) How are substrates selected for tagging and degradation?
4) What is the molecular basis of antibiotics that operate by disrupting proteasomal protein degradation?
We study the transcriptomic and proteomic adaptation of yeasts to changing nutrient environments, as well as their domestication and fermentation to better understand yeast performance and potentially develop strategies and predictions of fermentation efficiencies and flavour compound production during alcoholic fermentations. We also look at yeast diversity and the unique flavour compounds that could expand product diversity in the wine, beer and cider industries.Learn More
Many of the signaling pathways that are involved in development are also involved in the onset and progression of disease. As an example, the Wnt signaling pathway is required during many stages of development and in the homeostasis of stem cells in the adult. Perturbation of this pathway in stem cells in the adult often leads to cancer. It is now known that greater than 90% of colorectal cancers are caused by mutations in the Wnt signaling pathway. As this pathway is important for both proper development and disease, I am curious to know how this pathway can turn it self on and off so many times during development and why it fails to turn off in disease. The lab focuses on two negative feedback regulators of Wnt signaling: Nkd1 and Axin2.Learn More
My research focuses on asymmetric RNA localization and localized translational control in animal species. I have also studied asymmetric RNA localization in neural stem cells and their contribution to both cellular differentiation and cortical development across species. Currently, my students and I are investigating various proteins that we think are important for RNA regulation during brain development.Learn More
My research explores biodiversity from different perspectives and scales. We have develop molecular diagnostic tools for plant identification, including herbal product authentication and certification. Also, we contribute to the Plant Barcode of Life, investigating intra and interspecific variation in plants, and incorporate both Indigenous knowledge and DNA-based approaches to understanding diversity. In addition, I have extensively researched the effects of ecosystem management on community structure. Lastly, I am engaged in the scholarship of teaching and learning and have recently looked at 1) learning objects as mechanisms of engagement, 2) active learning within large first year biology classes, and 3) ancient pedagogies.Learn More
My research focuses on three main areas of plant cell biology:
1) Characterization of enzymes involved in seed oil biosynthesis.
2) Understanding various aspects of the biogenesis of peroxisomes, including how membrane proteins are targeted to this organelle, and what role the endoplasmic reticulum (ER) serves in the formation of peroxisomes.
3) Identification and characterization of a unique class of integral membrane proteins known as "Tail-Anchored" (TA) proteins.
My lab studies:
1) Large-scale genome evolution, with a focus on the "C-value enigma," transposable elements, and whole-genome duplications.
2) DNA quantification methods to measure nuclear DNA content.
3) DNA-based methods for species identification and questions in evolutionary biology to understand how biological diversity arises at all levels.
4) Genome size evolution to understand the operation of natural selection and other evolutionary principles.
5) The interface between Integrative Genomics and Evolutionary Biology, otherwise disconnected fields within the biological sciences.
I study evolution in heterogeneous environments, over large geographic ranges, and in the presence of variable species assemblages by using computational approaches and bioinformatics techniques to analyze large, high-resolution genomic datasets. My work revolves around two focal questions: 1) How consistent are evolutionary and ecological outcomes of species interactions? and 2) To what extent are species evolutionarily cohesive across their ranges? Most of the fish species I study are affected by human-mediated disturbances, including species introductions and fragmentation of aquatic habitat by dams. I use large genomic, ecological, and isotopic datasets to understand how evolutionary processes function across ecological contexts.Learn More
My primary research interest concerns the splendid array of compounds that are made by plants and the underlying molecular and biochemical basis of their synthesis. My lab focuses on natural products that are of medicinal, industrial or pharmacological relevance and on specialized metabolites that help plants cope with their dynamic environment. As an example, we investigate the biosynthesis, composition and structure of plant-derived polyisoprenoids. We also work closely with collaborators in various fields such as organic chemistry, food science, neurobiology, and ecology with the overall goal to shed light on the processes that operate at the interface of plant primary and secondary metabolism.Learn More
My lab aims to understand 1) the molecular genetic mechanisms of recombination in mammalian cells; 2) how defects in recombination contribute to tumorigenesis; and, 3) the nature of recombination hotspots. We are presently researching questions pertaining to: the mechanism and frequency of recombination in mammalian cells; the role of large palindromes in promoting recombination; mammalian heteroduplex DNA formation and repair; genetics of strand invasion and 3' end polymerization; how DNA sequences act to stimulate recombination; non-crossover mechanisms of homologous recombination; the genetic control of recombination.Learn More
As they are literally rooted in place, plants possess remarkable mechanisms that perceive, interpret, and respond to internal and external cues so as to optimise plant growth and development relative to prevailing environment conditions. Despite the incredible diversity in plant forms, the molecular mechanisms that control plant responses to internal and external cues are highly conserved across diverse genera. The timing and localisation of these mechanisms shape plant and development. Our research team aims to gain greater insights into molecular mechanisms that plants employ to convert internal cues and external signals into appropriate adjustments in resource acquisition and allocation, focusing on the role of gene regulation in conditioning these adjustments.Learn More
One of the fundamental questions in plant biology concerns the nature of the signals that bring about the transition from vegetative to reproductive growth. My research is aimed at characterizing the developmental signals that cause plants to flower. The primary focus of this work is the maize indeterminate gene (id1). Maize plants that lack id1 function flower extremely late, or not at all, and they exhibit abnormal flower development. The ID1 protein contains zinc-finger motifs, suggesting that it regulates the expression of other genes. Expression analysis reveals that id1 mRNA is expressed only in leaf tissue, suggesting that ID1 acts by controlling the production of leaf-derived signals that mediate the transition to flowering.Learn More
Much of our current effort is focused on understanding the regulation of starch synthesis in storage tissues such as the developing seeds of cereals. Starch is the major determinant of yield in such crops, and has wide application in both the food and non-food industries, yet there remain a huge number of unknowns in what limits the production and structure of this important glucan polymer. There is also an increasing realization that different types of starch provide benefits for human health. Our research covers cereals such as maize, barley, rice, and wheat, as well as the model organism Arabidopsis thaliana. I lead a large, interdisciplinary team whose expertise includes plant biochemistry, genetics, molecular biology, microbiology, human physiology, and nutrition.Learn More
For bacteria, survival requires evading detection. Pathogens must evade their host, but all bacteria need to avoid being targeted by phages. Gram negative bacteria’s survival depends on lipopolysaccharide and capsule – highly complex carbohydrate molecules that coat their outer surface. The enzymes that produce these molecules are complex, drawing on a large set of basic modules but then tweaking and combining them into new organizations that accomplish unique ends. My lab is focused on understanding how the structures and large-scale architectures of these enzymes create the enormous variety of unique custom carbohydrates observed in nature. To this end, we use crystallography, enzymology, and a variety of biophysical assays and bioinformatics tools to better understand these proteins.Learn More
While animal models have lead to huge advancements in our understanding of neurobiology, there is controversy over whether overexpression/silencing of gene expression is representative of diverse disease states. Indeed, the lack of availability of primary human neurons has made evaluating the pathological consequences of genomic mutations arduous. The use of human induced pluripotent stem cell (hiPSC) technology overcomes these limitations by providing a source of human neurons from both normal and disease genetic backgrounds. We currently focus on stem cell based models of Parkinson's Disease (PD) to study how mitochondrial stress mechanisms impact on neuronal function in human disease.Learn More
My lab examines the control mechanisms underpinning starch biosynthesis in leaf chloroplasts (which make starch during the daytime, and degrade it at night) of the model plant Arabidopsis thaliana, and non-photosynthetic amyloplasts of cereal endosperms such as maize, wheat, barley and rice which make storage starches. More specifically, we are interested in the biochemical control mechanisms governing the many enzymes and enzyme classes which make up the core pathway of starch biosynthesis. This involves investigating the role of protein-protein interactions and protein phosphorylation in coordinating the proteins involved in starch synthesis and degradation within the plastid to produce the highly ordered and complex structure of the starch granule.Learn More
Morphological studies have provided an outline of biodiversity, but are incapable of surveying, managing and protecting it on a planetary scale. By exploiting two technologies that are gaining power exponentially – DNA sequencing and computational capacity – my research promises an ever-accelerating capacity to monitor and know life. In particular, I aim to automate species identification and discovery, and to employ this capacity to answer longstanding scientific questions. Automation is possible because sequence diversity in short, standardized gene regions (DNA barcodes) enables fast, cheap, and accurate species discrimination. New instruments can inexpensively gather millions of DNA sequences, enabling surveys of organismal diversity at speeds and scales that have been impossible.Learn More
We currently have several projects in various areas that explore aspects of the gut microbiome and beyond:
1) Understanding how gut microbes are involved in the modulation of disease in colorectal cancer, diabetes, infection, and inflammatory bowel diseases
2) Isolation and characterisation of hunter-gatherer people's gut microbiome in an effort to discover novel microbial species and understand their function
3) Characterisation of the non-bacterial microbes of the human microbiome and their functions
4) Building model systems to study human gut microbes in vitro and in vivo
5) The study of 'oncomicrobes' (in particular, Fusobacterium nucleatum), and the development of colorectal cancer.
6) Translation to the clinic - development of 'microbial ecosystem therapeutics'