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  • 1.
    Kiefer, Christian
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Characterisation of actin cytoskeletal functions and interactions during planar polarity formation in Arabidopsis2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The establishment of cell and tissue polarity is essential for the development of eukaryotic organisms including plants and animals. When cell polarity is uniformly organised within a plane of a single tissue layer, it is referred to as planar polarity. In the model plant Arabidopsis thaliana, the polarly organised formation of root hairs towards the basal (root tip-oriented) ends of epidermal cells provides an ideal model system to study planar polarity formation. The instructive cue which uniformly organises tissue polarity in the Arabidopsis root epidermis is a concentration gradient of the plant hormone auxin. This concentration gradient leads to the polar recruitment of Rho-of-plant proteins to membrane sites where root hairs will form, making them the earliest cellular markers of planar polarity. Despite having identified several of the components required for planar polarity formation and the cellular read-out of it, little is known about how planar polarity is perceived and stably executed on the single cell level. Recently, a role for ACTIN2 in polar hair positioning was described, suggesting that actin may be involved in the cellular read-out of planar polarity.

    In the work presented here, we further investigate the contribution of the actin cytoskeleton to polar hair positioning. We identify a role for actin upstream of polar Rho-of-plant (ROP) positioning and describe ACTIN7 and ACTIN-INTERACTING PROTEIN1-2 (AIP1-2) as components required for planar polarity formation which interact directly in yeast and in vitro and genetically during planar polarity formation. AIP1-2 expression proves hair cell file-specific and depends on WEREWOLF function, revealing a link between planar polarity and cell fate patterning in the root. In addition we find that ACT7 genetically interacts with SABRE (SAB) and that actin and SAB co-localise at the cell plate and plasma membrane domains during cell division. Furthermore, we show that actin is not only involved in the positioning, but also in the organisation of the polar membrane domain which marks where a root hair will form. Among the components which localise at this site are the phosphoinositide-biosynthetic enzyme PHOSPHATIDYLINOSITOL 4-PHOSPHATE 5-KINASE3 (PIP5K3), the DYNAMIN-RELATED PROTEINs (DRPs) DRP1A and DRP2B, the D6 PROTEIN KINASE (D6PK) and membrane sterols. For several of these components, we report a function in planar polarity formation and in the organisation of the hair initiation site.

    With this work, we provide deeper insight into the function of the actin cytoskeleton and its interactions during planar polarity formation and identify additional components that contribute to the process. Moreover, we report AIP1-2 placement under control of the cell fate patterning system during establishment of planar polarity. Our results provide stepping stones for future studies aimed at investigating the mechanistic processes that contribute to planar polarity formation in more molecular and cellular detail.

  • 2.
    Kiefer, Christian
    Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Hur påverkar nivån på kemiundervisningen elevers intresse för ämnet kemi?2015Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I Sverige finns det idag ett sviktande intresse för kemi bland framtida studenter, trots att aktuella prognoser visar att det inom en snar framtid väntas ett större antal pensionsavgångar i kemisektorn och behovet av kemister därmed kommer att öka. En fråga som ställs är vart det trytande intresset kommer ifrån. Då gymnasieskolan är språngbrädan för ungdomars framtida karriär har ett stort fokus riktats mot att förstå hur gymnasieelevers intresse för ämnet kemi ser ut och hur man kan påverka det.

     

    I detta arbete har jag med hjälp av en enkät- och kompletterande intervjuundersökning försökt kartlägga hur den innehållsmässiga fördjupningsnivån som kemiundervisningen läggs på kan påverka elevers intresse för ämnet kemi. Studien, som omfattade 70 elever som precis läst färdigt kursen Kemi 2 på ett gymnasium i en mellanstor svensk stad, visar att det finns en potential att öka elevintresset för kemi genom att antingen lägga undervisningen konstant på en innehållsmässigt något högre nivå, eller genom att göra kortare tillfälliga fördjupningar där enstaka aspekter av kemins vardag förklaras på ett mer detaljerat sätt. Bland förklaringarna till att en höjning av fördjupningsnivån i kemiundervisningen kan bidra till ett ökat elevintresse är att eleverna är intresserade av kemin i sig och gärna vill ha en bättre förståelse för den, samt att en fördjupad förståelse för kemi av eleverna ofta förstås som en mer välgrundad kännedom om vardagliga saker som sker omkring oss.

  • 3.
    Kiefer, Christian S.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Claes, Andrea R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Nzayisenga, Jean-Claude
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Pietra, Stefano
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Stanislas, Thomas
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hueser, Anke
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ikeda, Yoshihisa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). nstitute of Biochemistry and Biology, Plant Physiology, University of Potsdam, Germany.
    Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity2015In: Development, ISSN 0950-1991, E-ISSN 1477-9129, Vol. 142, no 1, p. 151-161Article in journal (Refereed)
    Abstract [en]

    The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity.

  • 4.
    Nakamura, Moritaka
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Kiefer, Christian S.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Planar polarity, tissue polarity and planar morphogenesis in plants2012In: Current opinion in plant biology, ISSN 1369-5266, E-ISSN 1879-0356, Vol. 15, no 6, p. 593-600Article, review/survey (Refereed)
    Abstract [en]

    Plant tissues commonly undergo morphogenesis within a single tissue layer or between associated cells of the same tissue type such as vascular cells. Tissue morphogenesis may rely on an underlying tissue polarity marked by coordinated unidirectional asymmetric localisation of molecules to ends of cells. When observed in the plane of the tissue layer this is referred to as planar polarity and planar morphogenesis. However, planar morphogenesis can also involve multidirectional or differential growth of cells relying on cell-cell communication. Here, we review recent progress towards an understanding of hormonal coordination and molecular mechanisms underlying planar and tissue polarity as well as planar morphogenesis. Furthermore, we discuss the role of physical forces in planar morphogenesis and the contribution of tissue polarity to plant organ shape.

  • 5.
    Pietra, Stefano
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustavsson, Anna
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Kiefer, Christian
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Kalmbach, Lothar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hörstedt, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå Core Facility Electron Microscopy, Umeå University.
    Ikeda, Yoshihisa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Stepanova, Anna N.
    Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695, USA.
    Alonso, Jose M.
    Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695, USA.
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Arabidopsis SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity2013In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, p. 2779-Article in journal (Refereed)
    Abstract [en]

    The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes.

  • 6.
    Stanislas, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Institute of Biochemistry and Biology, Plant Physiology, University of Potsdam, Potsdam-Golm, Germany.
    Hüser, Anke
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Kiefer, Christian
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). christian.kiefer@umu.se.
    Brackmann, Klaus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria.
    Barbosa, Inês C.R.
    Technical University Munich, Plant Systems Biology, Freising, Germany.
    Gustavsson, Anna
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Pietra, Stefano
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schwechheimer, Claus
    Technical University Munich, Plant Systems Biology, Freising, Germany.
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Institute of Biochemistry and Biology, Plant Physiology, University of Potsdam, Potsdam-Golm, Germany.
    D6PK AGCVIII kinase is a lipid domain-dependent mediator of Arabidopsis planar polarityManuscript (preprint) (Other academic)
1 - 6 of 6
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