Plant cell biology
Professor Chris Hawes, Professor David Evans, Dr John Runions, Dr Christine Faulkner, Dr Anne Osterrieder, Dr Katja Graumann
The plant cell biology laboratories incorporate the microscopy and bioimaging facilities (TEM, SEM, fluorescence, Zeiss LSM 510 Meta confocals) of the Research School and includes a fully equipped molecular/biochemistry laboratory, greenhouse and plant cell culture facilities. The main research theme of the group is the study of the flow of membrane, and the transport of proteins within the endomembrane system in plant cells from the nuclear envelope through to the plasma membrane, the proteins organising the system, organelle biogenesis and the response of cells to pathogen attack. Major strengths of the group are in the application and development of fluorescent protein technology for the in vivo imaging of plant cells by confocal microscopy, immunocytochemistry and electron microscopy. The annual Cell Imaging course of the Royal Microscopical Society is run by members of the Group.
Professor Chris Hawes, Department Research Lead and Postgraduate Tutor
The organisation of the endoplasmic reticulum in plant cells:
The cortical endoplasmic reticulum (ER) in plant cells is a highly structured dynamic network of tubules and small cisternae over which, in some tissues such as leaf epidermis, the Golgi bodies move. We have recently shown that both tubules can grow out from the network and that the surface of the ER membrane itself is moving in an actin-dependent manner. We are currently investigating the role of two families of ER membrane proteins, the reticulons and RHD3 proteins, in the establishment of the cortical ER during cell plate and plasmodesmata development and the maintenance of the cortical network in interphase cells. This work has been supported by the B a Leverhulme Trust grant and a current BBSRC grant.
Plant Golgi dynamics and biogenesis:
We have previously shown that in many plant cell types the Golgi bodies are dynamic travelling over the ER network as distinct secretory units. Live cell imaging utilising fluorescence recovery after photobleaching technology has demonstrated cargo transport between the ER and Golgi. Several interlinked projects are currently being undertaken on the plant Golgi. The distribution of transferases and other enzymes within the Golgi stack are being investigated by live cell imaging a and the differential fate of Golgi membranes and proteins upon Golgi destruction and biogenesis is being established. In a BBSRC funded project a number of peripheral Golgi “matrix” proteins have been identified and their role in maintenance of Golgi structure and in Golgi biogenesis is being investigated. Interactions between the Golgi matrix proteins and between matrix proteins and regulatory GTPases (Rabs) are being investigated using live cell imaging, optical tweezers and fluorescence resonance energy transfer (FRET) techniques.
BBSRC, Leverhulme Trust, STFC.
Dr Verena Kriechbaumer, BBSRC postdoctoral researcher
Ms Petra Kivinimie, Research Student
Ms Alessandra Rochetti, Research Student
Dr Imogen Sparkes, Exeter University
Dr Lorenzo Frigerio, University of Warwick
Prof. Karl Oparka, University of Edinburgh
Drs Jennifer Schoberer & Richard Strassa, BOKU, Vienna
Dr Tijs Ketelaar, Wageningen University
Drs Stan Botchway & Andy Ward, Rutherford Appleton Laboratories
Professor David Evans, Head of Department & Faculty Postgraduate Tutor
The plant nuclear envelope is a surprisingly poorly understood system and the research of the group is concentrated on identifying native plant nuclear envelope proteins and studying their properties. The nuclear envelope is a dynamic system that undergoes massive changes in the cell cycle and is closely interlinked with the nucleoskeleton and cytoskeleton. While a few nuclear envelope proteins are conserved between animals, plants and yeast, many are not and there are significant differences that require exploration.
We are using fluorescent protein technology to study the location, role and traffic of newly described proteins at the nuclear envelope, especially during the cell cycle and have developed a family of fluorescent nuclear envelope probes. This work is in collaboration with Professor Iris Meier at Ohio State University USA and Professor Christophe Tatout, Université Blaise Pascal, Clermont Ferrand, France.
Mechanisms for the targeting and retention of inner nuclear envelope proteins:
Using chimaeric fluorescent constructs of the human lamin B receptor and plant SUN domain proteins we have undertaken studies of the mechanisms, conserved between kingdoms, that permit targeting to the plant nuclear envelope. Using data obtained from mutants in which key targeting and binding domains have been deleted, we developed a model for inner nuclear envelope location of proteins in plants and are continuing this work with native plant proteins.
Localisation and function of novel nuclear envelope proteins in plants:
Using a bioinformatics approach we have identified homologues of animal and yeast nuclear envelope proteins in plants and, with our collaborators are continuing to expand knowledge of the higher plant proteome. We first characterised proteins containing SUN domains as part of the plant LINker of Nucleoskeleton and Cytoskeleton (LINC) complex in plants and have continued to identify binding partners and to characterise the function of the complex in plants. This work has been funded by the Leverhulme Trust and commercial applications of it by the Higher Education Innovation Fund (HEIF).
Recent: Leverhulme Trust
Current: Higher Education Innovation Fund, Oxford Brookes University
Dr Sarah Smith - Research Associate
Mrs Vidya Pawar - Research Student
Dr Katja Graumann and Dr John Runions, Oxford Brookes University
Dr Susan Armstrong, University of Birmingham
Prof Iris Meier, Ohio State University, USA
Prof Christophe Tatout and Dr Emmanuel Vanrobays, Université Blaise Pascal, Clermont Ferrand, France
Dr John Runions, Reader in Cell and Molecular Biology
Proteins are constantly in flux in living cells. My laboratory utilises advanced imaging techniques to visualise proteins in different organelles including the cell membrane, cell wall, and the cytoskeleton. A central question in cell biology is 'how do cells recognise changes in their environment and what mechanisms do they employ to respond to these?'
Fluorescent proteins are naturally occurring in some animals and have been co-opted by cell biologists for the study of all types of organism including plants. I use fluorescent protein technology to monitor protein interactions at the cell surface. To see these proteins clearly, even deep within tissues, we use high-power laser microscopes. My most recent research is using a new type of laser excitation of fluorescent proteins that lets us study the behaviour of single molecules within membranes.
Recent findings within my laboratory include the discovery of a protein which spans the cell membrane to connect the cell’s internal support structure with the external, enveloping cell wall. This protein provides a scaffold that helps maintain cellular structure. Related research has led to the finding that the cell wall of plant cells is responsible for stabilising proteins within the cell membrane. Importantly, this provides a mechanism by which plants can immobilise signalling receptors on their surface so that they are prepared to respond to stresses such as pathogen attack.
A new BBSRC grant has provided funding so that I can continue with this research. This next phase of the work will continue to study the continuum of connection at the cell surface in cell-wall mutant backgrounds so that we can establish how the interrelationship between cell membrane and cell wall works.
Frances Tolmie - Research Student
Drs Stan Botchway and Marissa Martin-Fernandez, STFC, Rutherford Appleton Labs.
Dr Christine Faulkner, Research Fellow in Plant Cell Biology
How do plant cells communicate with each other when under attack?
Cell-to-cell communication is a fundamental biological process, necessary for co-ordination of development and environmental responses in multicellular organisms. In plants, intercellular channels called plasmodesmata connect neighbouring cells. Plasmodesmata are known to regulate the flow of metabolites, larger molecules such as transcription factors, and even some classes of pathogens from cell-to-cell. Regulation of cell-to-cell connectivity via plasmodesmata is required for developmental transitions such as the induction of flowering and lateral root formation, but we do not yet understand how cell-to-cell communication and intercellular flux is controlled in response to external stimuli such as pathogen attack. When a plant is attacked by a pathogen, defence responses involve the co-ordinated action of groups of cells that communicate through chemical and physical signals. Many chemical signals associated with defence responses (reactive oxygen species (ROS), calcium, nitric oxide, salicylic acid, jasmonic acid and ethylene) are small enough to diffuse from one cell into another through plasmodesmata and it has been hypothesised that the opening and closing of these channels controls the location and activity of these defence-associated molecules and their efficacy in defence responses.
I use fluorescent dyes and proteins to trace which cells are connected (and therefore communicating) during attack by fungal and oomycete pathogens. Using the plasmodesmal proteome I aim to identify proteins that control plasmodesmal opening and closing in the presence of a pathogen. By examining the function of these proteins and characterising the mechanisms that they use to open or close plasmodesmata I will determine how to exploit these proteins to increase plant resistance to harmful pathogens.
Dr Silke Robatzek, the Sainsbury Laboratory, Norwich
Prof. Jonathan Jones, the Sainsbury Laboratory, Norwich
Prof. Volker Lipka, University of Goettingen
Prof. Karl Oparka, University of Edinburgh
Dr Anne Osterrieder, Research & Science Communication Fellow
The Golgi apparatus lies in the centre of the secretory pathway, a complex membrane system conserved in all eukaryotic cells. It is similar to a compartmentalised conveyor belt system in a factory: it processes, distributes and stores a wide range of important proteins such as storage proteins in cereal grains or proteins involved in plant stress responses. In animal cells the Golgi apparatus is organised as a single large ribbon. A plant cell however can have up to hundreds of small mobile Golgi bodies which move along the cytoskeleton over the endoplasmic reticulum (ER). Golgi bodies contain enzymes that attach sugars to proteins, they pack and ship protein cargo and lipids and produce material for the cell wall.
Tethering factors take over a range of important functions at the Golgi apparatus and the ER-Golgi interface, such as the regulation of protein transport or the formation and maintenance of the polarised Golgi stack. I am interested in characterising plant tethering factors at the cis-Golgi (in collaboration with Prof Chris Hawes) and at the trans-Golgi face and trans-Golgi network. In collaboration with Drs Stan Botchway, Mark Pollard and Andy Ward I am using and developing advanced laser-based bioimaging methods such as fluorescence lifetime imaging (FLIM) to test protein-protein interactions and optical laser tweezers to micromanipulate Golgi bodies in living plant cells.
A new project in collaboration with Dr Irene Mueller-Harvey (University of Reading) and Riitta Julkunen-Tiitto (University of Eastern Finland) will explore the use of bioimaging methods to study the subcellular localisation of plant secondary metabolites and enzymes required for their synthesis.
I am passionate about making science accessible to non-experts and encourage dialogue between researchers and the public. I co-ordinate a number of public engagement events for the Faculty of Health and Life Sciences in collaboration with staff and students from the Faculty and from the Oxford Brookes Poetry Centre. These events include the annual Brookes Science Bazaar, interdisciplinary partnerships between sciences and humanities, events for the 'Amazing Acts' Festival at the Pegasus Theatre, ‘CSI Oxfordshire’ and internal public engagement training sessions.
I am also using social media networks such as Twitter or YouTube to engage diverse audiences online, and blog about science, outreach and science communication at http://www.plantcellbiology.com and http://www.extelligenceexperiment.com. I run online engagement training workshops for researchers at Oxford Brookes and for the Society of Experimental Biology and the Royal Microscopical Society.
Oxford Brookes University
Drs Stan Botchway, Andy Ward and Mark Pollard, Rutherford Appleton Lab, STFC
Dr Paola Tosi, Rothamsted
Dr Irene Mueller-Harvey, Reading University
Dr Riitta Julkunen-Tiitto, University of Eastern Finland
Dr Jennifer Schoberer and Richard Strasser, BOKU, Vienna
Dr Katja Graumann, Leverhulme Research Fellow
My research expertise is in the field of nuclear envelope (NE) biology. My work is associated with that of Prof David Evans group and I am using my Leverhulme Trust funded Early Career Fellowship to advance my research on plant NE protein functions and interactions throughout the cell cycle.
Investigating the SUN domain protein family at the plant NE
The Sad1-Unc84 (SUN) domain family consists of two main groups – the classical C-terminal SUN domain proteins and the mid-SUN proteins. Previously, I identified and characterised the two classical C-terminal SUN domain proteins – AtSUN1 and AtSUN2 – in plants. Current work is focussing on the three mid-SUN proteins AtSUN3, AtSUN4 and AtSUN5. Interactions between C-terminal SUN proteins and mid-SUN proteins as well as localisation and expression of AtSUN3/4/5 are being investigated; work which is supported by a collaboration with Prof Christophe Tatout.
Protein interaction networks at the plant NE
In addition to SUN proteins interacting with each other, various NE integral and associated proteins are being examined as putative SUN interaction partners. One group of proteins that is under investigation are Nuclear Envelope Associated Proteins (NEAPs) 1, 2 and 3. They were identified in a bioinformatics approach as putative NE proteins localised at the nuclear periphery. Further characterisation studies of NEAPs are currently carried out by Vidya Pawar, a PhD student co-supervised Prof David Evans and me.
Klarsicht/Anc1/Syne1 homology (KASH) domain proteins are the classical interactors of SUN proteins. In animal and yeast, the SUN-KASH complexes form bridges across the NE that directly link the cytoskeleton with the nucleoskeleton and chromatin. These nucleo-cytoskeletal bridging complexes are essential for chromatin organisation in interphase and division, nuclear shape as well as positioning and movement of the nucleus in response to external stimuli. My research led to the recent identification of the first plant KASH protein and characterising this SUN-KASH interaction. We currently are investigating the cytoskeletal connections of these complexes. This work is carried out in collaboration with Prof Iris Meier and Dr Imogen Sparks.
In addition to NEAPs and KASH proteins, I am also trying to identify other SUN interactors by screening cDNA libraries in a membrane bound yeast two hybrid system and co-immunoprecipitation with SUN proteins as bait. The aim is to piece together a network of protein interactions based on SUN proteins at the plant NE and identifying novel plant NE proteins. This work is carried out together with Prof Tatout and Prof Dorothy Shippens.
The Leverhulme Trust Early Career Research Fellowship
Oxford Brookes University/Higher Education Innovation Fund
European Molecular Biology Organisation Short Term Fellowships
Mrs Vidya Pawar, PhD student with Prof. D. Evans
Dr Sarah Smith, Research Associate
Dr Sue Armstrong, University of Birmingham, Birmingham, UK
Prof Christophe Tatout, Blaise Pascal University, Clermont-Ferrand, France
Prof Iris Meier, Ohio State University, Columbus, USA
Prof Dorothy Shippen, Texas A&M University, College Station, USA
Dr Hillary Rogers, Cardiff University, Cardiff, UK
Dr Imogen Sparks, University of Exeter, Exeter, UK