CSB Deptl Seminar: Prof. Christian Hardtke, Dept of Plant Molecular Biology, University of Lausanne

CSB Departmental Seminar

Prof. Christian Hardtke
Department of Plant Molecular Biology
University of Lausanne

"Autocrine Peptides, Self-organization and Zombie Cells: Molecular Switches in Phloem Formation"

Friday, November 13, 2015 at 2 p.m.
Ramsay Wright Building, Room 432

Host: Prof. Thomas Bertleth  <thomas.berleth@utoronto.ca>

Abstract:
The evolution of the plant vascular system has had a crucial impact on the biosphere and earth history, because it enabled plants to effectively colonize land. Plant vasculature comprises two distinct transport systems, xylem and phloem. Xylem consists of connected vessels, which transport water and nutrients extracted from the soil to the rest of the plant body. Phloem is a more complex and versatile tissue, which distributes photosynthetic sugars, nutrients as well as developmental signals throughout the plant, typically from source to sink organs. Phloem sap conduits are formed by connected sieve elements, whose differentiation includes cell elongation, wall thickening and enucleation. Little is known about the molecular-genetic control of this vital differentiation process. The growth apices of plants, the meristems, connect to established vasculature via continuous production of early phloem, so-called protophloem. An ideal system to investigate this process is the Arabidopsis root meristem, where protophloem strand formation can be followed along the spatio-temporal gradient of single cell files. Over the last years, we have defined a molecular-genetic network that consists of two antagonistic modules and guides the formation of root protophloem sieve elements, starting from their stem cells. The positive regulators include polar plasma membrane-associated proteins that localize opposite to each other, while the negative regulators comprise receptor-like kinase signalling pathways that convey the response to autocrine peptide ligands. Because all positive and negative regulators identified so far are expressed from the beginning to the end of the differentiation process, developing protophloem cells must eventually escape their autocrine peptide signals to switch from proliferation to differentiation in a self-organizing spatio-temporal manner.

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CSB Deptl Seminar: Dr. Youssef Belkhadir, Gregor Mendel Institute of Molecular Plant Biology, Vienna, Austria

CSB Departmental Seminar

Dr. Youssef Belkhadir
Gregor Mendel Institute of Molecular Plant Biology
Vienna, Austria

"Design Principles and Self-Assembling Properties of the Extracellular Interactome in Arabidopsis"

Friday, October 23, 2015 at 2:00 p.m.
Ramsay Wright Building, Room 432

Host:  Prof. Darrell Desveaux <darrell.desveaux@utoronto.ca>

Abstract: 
In plants, an expanded family of cell-surface receptor kinases (RKs) transduce either ‘self’ or ‘non‐self’ signals into changes in nuclear gene expression. Plant RKs are typically characterized by an extracellular domain, a single transmembrane pass and in most cases, a functional intracellular kinase domain. Extracellular domains (ECDs) can modulate the activity of signaling competent RKs complexes by controlling ligand specificity and by recruiting appropriate signaling partners. Owing to the inherently transient nature of their interactions and bottlenecks with their expression in heterologous systems, there is very limited knowledge on the global interaction network ECDs can establish in their resting or ligand-activated functioning modes. I will present our genome-scale efforts aimed at discovering novel ECD interactions in the RKs repertoire of Arabidopsis.

 

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CSB Deptl Seminar: Dr. Jeffrey Leung, Seed Biology, Department of Institut Jean-Pierre Bourgin, INRA, Versailles, France

CSB Departmental Seminar

Dr. Jeffrey Leung
Seed Biology
Department of Institut Jean-Pierre Bourgin
INRA, Versailles, France

"The Plant's Dilemma: Managing the Competing Priorities between Water Economy and a Positive Carbon Budget"

Friday, Oct 30, 2015 at 2:00 p.m.
Ramsay Wright Building, Room 432

Host:  Prof. Eiji Nambara <eiji.nambara@utoronto.ca>

Abstract:

In the opening salvos of his engaging article, How Stomata Resolve the Dilemma of Opposing Priorities, K. Raschke (1976) wrote that "Land plants are in a dilemma throughout their lives: assimilation of CO2 from the atmosphere requires intensive gas exchange; the prevention of excessive water loss demands that gas exchange be kept low." What seemed a rarefied musing of a plant academic nearly 40 years ago has since broadened into global environmental concerns. My work into how higher plants in an open field juggle this conflicting need for an abundance of both H2O and CO2 to drive photosynthesis has led me to identify the metabolite, acetylated 1, 3-diaminopropane, that seems to trigger a risk-taking behavior in C3 plants to assimilate CO2 despite the potential for tissue dehydration.

Citation:

Raschke, K. (1976) How stomata resolve the dilemma of opposing priorities. Phil. Trans. R. Soc. B. Biol. 273, 551-560.

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CSB Special Seminar: Prof. Kentrao Inoue, Department of Plant Sciences, University of California at Davis

CSB Special Seminar

Professor Kentrao Inoue
Department of Plant Sciences
University of California at Davis

"Chloroplast Evolution - the Requirement and Adaptation of Protein Transport"

Wednesday, Oct 14, 2015 at 1:00 p.m.
Earth Sciences Centre, Room 3087

Host:  Prof. Keiko Yoshioka <keiko.yoshioka@utoronto.ca>

Chloroplast evolution began when the ancestral cyanobacterium was engulfed by a eukaryotic cell and became an endosymbiont. Successful conversion to the chloroplast depended on relocation of the genes from the endosymbiont to the host nucleus. This process required establishment of the protein import apparatus that allows uptake of cytosolically-synthesized proteins across the double-membrane envelope of the pre-organelle. In bacteria, membrane protein insertion usually occurs co-translationally. By contrast, nuclear-encode proteins found in the thylakoid membrane within the chloroplast are targeted post-translationally, thus need a novel strategy that prevents pre-mature folding or aggregation of hydrophobic proteins. Our research is centered on protein transport, which is required for and adapted during chloroplast evolution. More specifically, we address various questions about the protein import channel Toc75 (for translocon at the outer-envelope-membrane of chloroplasts! 75) and its paralog OEP80 (for outer envelope protein 80). These proteins are present in the outer membrane and share the common ancestor with BamA, which are essential proteins found in the outer membranes of Gram negative bacteria but do not catalyze protein import. We also study targeting of Plsp1 (for plastid type I signal peptidase 1), a single-pass protein of bacterial origin, to the envelope and thylakoid membranes within the chloroplast. I will discuss how we got there and what we are excited about. Supported by NSF-MCB and DOE-BES.

Selected reference:

Midorikawa T, Endow, JK, Dufour J, Zhu J, Inoue K (2014) Plastidic type I signal peptidase 1 is a redox-depenent thylakoid processing peptidase. The Plant Journal, 80, 592-603.

Midorikawa T, Inoue K (2013) Multiple fates of nonmature lumenal proteins in thylakoids. The Plant Journal 76, 73-86.

Nafati M, Inoue K (2013) Indispensable roles of plastids in Arabidopsis thaliana embryogenesis - update. Advances in Genomic Science 1, 234-252.

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CSB Deptl Seminar: Prof. Rong Li, Director of Center for Cell Dynamics, Department of Cell Biology, Johns Hopkins University

CSB Departmental Seminar

Professor Rong Li
Director, Center for Cell Dynamics
Department of Cell Biology
Johns Hopkins University

"A Numbers Game: Rapid Cellular Evolution Driven by Karyotype Instability and Stoichiometry Imbalance"

Friday, Nov 6, 2015 at 2:00 p.m.
Ramsay Wright Building, Room 432

Host:  Prof. Rodrigo Fernandez-Gonzalez, IBBME <rodrigo.fernandez.gonzalez@utoronto.ca>

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CSB Deptl Seminar: Prof. Florence Marlow, Developmental and Molecular Biology, Neuroscience, Albert Einstein College of Medicine

CSB Departmental Seminar

Professor Florence Marlow
Associate Professor of Developmental and Molecular Biology
Associate Professor of Neuroscience
Albert Einstein College of Medicine

"Maternal Regulators of Oocyte Polarity and Germ Cell Development"

Friday, October 9, 2015 at 2:00 p.m.
Ramsay Wright Building, Room 432

Host: Prof. Ashley Bruce <ashley.bruce@utoronto.ca>

Abstract:
A key research goal of my group is to understand the molecular pathways and cellular events that establish the first developmental axis, the animal-vegetal axis. Since this process is maternally regulated, we use a combination of genetic, molecular, cell biological, and embryological approaches in the zebrafish model system to study oocyte polarity determination. This process was previously not readily tractable in vertebrates in part due a lack of mutants ablating oocyte polarity. Through maternal-effect genetic screens, mutants disrupting oocyte polarity were identified, including bucky ball (buc), the only known gene that is essential for formation of an ancient and conserved polarized structure of primary oocytes, the Balbiani body, and for establishment of early oocyte polarity in a vertebrate. These mutants together with mutants and transgenic models developed in my own lab, and the novel Buc-interacting partners that we have identified through genetic and biochemistry approaches, have provided unprecedented access and a very powerful system to gain mechanistic insight into a fundamental problem of cell and developmental biology- understanding the molecular basis of oocyte polarization and vertebrate animal-vegetal axis formation and germline specification. Our most recent work shows that establishment of oocyte polarity begins with the centrosome in cyst cells and that microtubule organizer activity requires centrosomal localization of Buc to promote oocyte polarity in zebrafish oocytes. We have also identified maternal factors that are necessary for germ cell specification and that promote germ granule formation in the embryo.

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CSB Special Seminar: Prof. Gina Poe, Anesthesiology/Molecular & Integrative Physiology, University of Michigan

CSB Special Seminar

Professor Gina Poe
Anesthesiology/Molecular & Integrative Physiology
University of Michigan

"Sleep to Remodel the Brain: Role for the Central Noradrenergic System and Its Absence"

Wednesday, October 7, 2015 at 3:00 p.m.
Ramsay Wright Building, Room 432

Host: Prof. John Peever <john.peever@utoronto.ca>

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CSB Seminar: Dr. James McKenna, Dept of Psychiatry/Division of Sleep Medicine & Research Services, Harvard Medical School & VA Boston Healthcare System

CSB Departmental Seminar

Dr. James McKenna
Dept of Psychiatry/Division of Sleep Medicine & Research Services
Harvard Medical School & VA Boston Healthcare System

"Neuroanatomical Investigations of Basal Forebrain GABAergic and Glutamatergic Neurons"
Friday, October 2, 2015
Ramsay Wright Building, Room 432 at 2:00 p.m.
Host:  Prof. John Peever  <john.peever@utoronto.ca>
Abstract:
The ascending reticular activating system (ARAS) is responsible for the cortical activation indicative of wakefulness. Our laboratory’s recent transgenic mouse models now allow detailed evaluation of GABAergic and glutamatergic neuronal subtypes in the basal forebrain, which is the ventral sub-cortical node of the ARAS. Such neuroanatomical validation allows further study of the role of basal forebrain GABAergic, cholinergic, and glutamatergic neurons in sleep-wake behavior, using in vitro and in vivo optogenetic approaches. Our findings indicate that basal forebrain cholinergic, glutamatergic, and GABAergic systems likely work synergistically to promote wakefulness and cortical activation.
Publications:
1: Kim T, Thankachan S, McKenna JT, McNally JM, Yang C, Choi JH, Chen L, Kocsis B, Deisseroth K, Strecker RE, Basheer R, Brown RE, McCarley RW. Cortically projecting basal forebrain parvalbumin neurons regulate cortical gamma band oscillations. Proc Natl Acad Sci U S A. 2015 Mar 17;112(11):3535-40. doi: 10.1073/pnas.1413625112. Epub 2015 Mar 2. Erratum in: Proc Natl Acad Sci U S A. 2015 May 26;112(21):E2848. PubMed PMID: 25733878; PubMed Central PMCID: PMC4371918.
2: Yang C, McKenna JT, Zant JC, Winston S, Basheer R, Brown RE. Cholinergic neurons excite cortically projecting basal forebrain GABAergic neurons. J Neurosci. 2014 Feb 19;34(8):2832-44. doi: 10.1523/JNEUROSCI.3235-13.2014. PubMed PMID: 24553925; PubMed Central PMCID: PMC3931499.
3: McKenna JT, Yang C, Franciosi S, Winston S, Abarr KK, Rigby MS, Yanagawa Y, McCarley RW, Brown RE. Distribution and intrinsic membrane properties of basal forebrain GABAergic and parvalbumin neurons in the mouse. J Comp Neurol. 2013 Apr 15;521(6):1225-50. doi: 10.1002/cne.23290. PubMed PMID: 23254904; PubMed Central PMCID: PMC3627393.

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CSB Deptl Seminar: Prof. Donald Fox, Pharmacology and Cancer Biology, Duke University School of Medicine

CSB Departmental Seminar

Professor Donald Fox
Pharmacology and Cancer Biology
Duke University School of Medicine

"Polyploidy and Aneuploidy in Organ Development"

Friday, October 16, 2015 at 2:00 p.m.
Ramsay Wright Building, Room 432

Host: Prof. Tony Harris <tony.harris@utoronto.ca>

Abstract:
My laboratory’s core focus is the biology of whole genome duplication, or polyploidy. Polyploidy was described shortly after the discovery of chromosomes, yet we still know little about its functions. Endopolyploid cells (polyploid cells in otherwise diploid organisms) are present in many human organs such as the heart and liver, and are present in increased proportions when these organs suffer injury. Further, recent sequencing of ~4,000 human tumors found polyploidy is an incredibly common event, supporting the hypothesis that polyploidy contributes to genome instability in diverse cancers. Intrigued by its frequent yet poorly understood occurrence in repairing and genomically unstable tissues, we developed the Drosophila hindgut as a genetically accessible tissue model to discover new, in vivo-relevant functions/mechanisms of polyploidy. Specifically, we study how polyploidy alters the genome during organ development, and the role of polyploidy in organ repair.

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CSB Seminar: Prof. Yves De Koninck, Director, Neurophotonics Centre, Psychiatry and Neuroscience, Director, Quebec Mental Health Institute

CSB Departmental Seminar
co-hosted with the Collaborative Program in Neuroscience

Professor Yves De Koninck
Director, Neurophotonics Centre
Professor of Psychiatry and Neuroscience
Scientific Director, Quebec Mental Health Institute

"New Tools to Probe the Brain with Light ..."

Location: Health Sciences Building 610 Auditorium at 155 College Street

Host:  Prof. Melanie Woodin  <m.woodin@utoronto.ca>

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