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Dissecting sterol function during clathrin-dependent endocytosis and cytokinesis in Arabidopsis thaliana
Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. (Markus Grebe)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sterols are lipid components of eukaryotic membranes. Alterations of membrane sterol composition perturb the execution of cell division, which in diverse eukaryotes can have severe consequences for development of the organism. Partitioning of the cytoplasm during cell division occurs at the final stage of cell division named cytokinesis. In somatic plant cells, cytokinesis is initiated by fusion of membrane vesicles in the plane of cell division resulting in a transient compartment termed the cell plate. Cell plate maturation relies on temporal and spatial orchestration of membrane fusion and endocytosis. Impaired vesicle fusion or defects in endocytosis result in cytokinetic defects.

In Arabidopsis thaliana, the KNOLLE and DYNAMIN-RELATED PROTEIN 1A (DRP1A) contribute to cytokinesis. KNOLLE mediates fusion of vesicles at the plane of cell division while DRP1A appears to be involved in cell plate maturation through its role in clathrin-mediated endocytosis.

This thesis shows that KNOLLE is specifically restricted to the cell division plane through sterol-dependent endocytosis that involves a clathrin- and DRP1A-mediated mechanism. Sterols affect internalization of KNOLLE through their role in lateral membrane organization by keeping diffusion of KNOLLE to lateral membranes in check via its endocytic removal. It is shown that the cell plate represents a high-lipid-order membrane domain that depends on the correct composition and the right concentration of sterols. Accumulation of DRP1A at the cell plate requires correct sterol concentration and composition similar to high-lipid order. Conversely, high-lipid-order at the cell plate relies on DRP1A activity suggesting a feedback between DRP1A function and lipid order establishment. Finally, it is shown that sterols are also present at the tonoplast of dividing and elongated root cells.

Taken together, the results reveal that formation of the cell plate in Arabidopsis thaliana depends on an intricate interplay between cytokinetic vesicle fusion, sterol-dependent lateral membrane and high-lipid-order domain organization as well as endocytic machinery function.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2013. , 64 p.
Keyword [en]
Arabidopsis, membrane, sterols, cytokinesis, KNOLLE, endocytosis, clathrin, DRP1A
National Category
Natural Sciences
Research subject
Developmental Biology; Molecular Biology; Molecular Cellbiology
URN: urn:nbn:se:umu:diva-80030ISBN: 978-91-7459-721-9OAI: diva2:646658
Public defence
2013-10-04, KBC-huset, KB3A9, Umeå Universitet, Umeå, 10:00 (English)
Available from: 2013-09-13 Created: 2013-09-09 Last updated: 2015-05-07Bibliographically approved
List of papers
1. Endocytosis restricts Arabidopsis KNOLLE syntaxin to the cell division plane during late cytokinesis
Open this publication in new window or tab >>Endocytosis restricts Arabidopsis KNOLLE syntaxin to the cell division plane during late cytokinesis
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2010 (English)In: EMBO Journal, ISSN 0261-4189, E-ISSN 1460-2075, Vol. 29, no 3, 546-58 p.Article in journal (Refereed) Published
Abstract [en]

Cytokinesis represents the final stage of eukaryotic cell division during which the cytoplasm becomes partitioned between daughter cells. The process differs to some extent between animal and plant cells, but proteins of the syntaxin family mediate membrane fusion in the plane of cell division in diverse organisms. How syntaxin localization is kept in check remains elusive. Here, we report that localization of the Arabidopsis KNOLLE syntaxin in the plane of cell division is maintained by sterol-dependent endocytosis involving a clathrin- and DYNAMIN-RELATED PROTEIN1A-dependent mechanism. On genetic or pharmacological interference with endocytosis, KNOLLE mis-localizes to lateral plasma membranes after cell-plate fusion. Fluorescence-loss-in-photo-bleaching and fluorescence-recovery-after-photo-bleaching experiments reveal lateral diffusion of GFP-KNOLLE from the plane of division to lateral membranes. In an endocytosis-defective sterol biosynthesis mutant displaying lateral KNOLLE diffusion, KNOLLE secretory trafficking remains unaffected. Thus, restriction of lateral diffusion by endocytosis may serve to maintain specificity of syntaxin localization during late cytokinesis.

National Category
Plant Biotechnology
Research subject
Physiological Botany
urn:nbn:se:umu:diva-31866 (URN)10.1038/emboj.2009.363 (DOI)000274233400004 ()19959995 (PubMedID)
Available from: 2010-02-19 Created: 2010-02-19 Last updated: 2015-05-07Bibliographically approved
2. The Endoplasmic Reticulum Is the Main Membrane Source for Biogenesis of the Lytic Vacuole in Arabidopsis
Open this publication in new window or tab >>The Endoplasmic Reticulum Is the Main Membrane Source for Biogenesis of the Lytic Vacuole in Arabidopsis
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2013 (English)In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 25, no 9, 3434-3449 p.Article in journal (Refereed) Published
Abstract [en]

Vacuoles are multifunctional organelles essential for the sessile lifestyle of plants. Despite their central functions in cell growth, storage, and detoxification, knowledge about mechanisms underlying their biogenesis and associated protein trafficking pathways remains limited. Here, we show that in meristematic cells of the Arabidopsis thaliana root, biogenesis of vacuoles as well as the trafficking of sterols and of two major tonoplast proteins, the vacuolar H+-pyrophosphatase and the vacuolar H+-adenosinetriphosphatase, occurs independently of endoplasmic reticulum (ER)-Golgi and post-Golgi trafficking. Instead, both pumps are found in provacuoles that structurally resemble autophagosomes but are not formed by the core autophagy machinery. Taken together, our results suggest that vacuole biogenesis and trafficking of tonoplast proteins and lipids can occur directly from the ER independent of Golgi function.

Place, publisher, year, edition, pages
American Society of Plant Biologists, 2013
National Category
Botany Cell Biology Biochemistry and Molecular Biology
urn:nbn:se:umu:diva-80178 (URN)10.1105/tpc.113.114827 (DOI)000326287100023 ()
Available from: 2013-09-11 Created: 2013-09-11 Last updated: 2015-05-07Bibliographically approved

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