| 1. |
- Dejonghe, Wim, et al.
(författare)
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Mitochondrial uncouplers inhibit clathrin-mediated endocytosis largely through cytoplasmic acidification
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- ATP production requires the establishment of an electrochemical proton gradient across the inner mitochondrial membrane. Mitochondrial uncouplers dissipate this proton gradient and disrupt numerous cellular processes, including vesicular trafficking, mainly through energy depletion. Here we show that Endosidin9 (ES9), a novel mitochondrial uncoupler, is a potent inhibitor of clathrin-mediated endocytosis (CME) in different systems and that ES9 induces inhibition of CME not because of its effect on cellular ATP, but rather due to its protonophore activity that leads to cytoplasm acidification. We show that the known tyrosine kinase inhibitor tyrphostinA23, which is routinely used to block CME, displays similar properties, thus questioning its use as a specific inhibitor of cargo recognition by the AP-2 adaptor complex via tyrosine motif-based endocytosis signals. Furthermore, we show that cytoplasm acidification dramatically affects the dynamics and recruitment of clathrin and associated adaptors, and leads to reduction of phosphatidylinositol 4,5-biphosphate from the plasma membrane.
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| 2. |
- Dong, Yang, et al.
(författare)
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HEARTBREAK Controls Post-translational Modification of INDEHISCENT to Regulate Fruit Morphology in Capsella
- 2020
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 30:19, s. 3880-3888
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Tidskriftsartikel (refereegranskat)abstract
- Morphological variation is the basis of natural diversity and adaptation. For example, angiosperms (flowering plants) evolved during the Cretaceous period more than 100 mya and quickly colonized terrestrial habitats [1]. A major reason for their astonishing success was the formation of fruits, which exist in a myriad of different shapes and sizes [2]. Evolution of organ shape is fueled by variation in expression patterns of regulatory genes causing changes in anisotropic cell expansion and division patterns [3-5]. However, the molecular mechanisms that alter the polarity of growth to generate novel shapes are largely unknown. The heart-shaped fruits produced by members of the Capsella genus comprise an anatomical novelty, making it particularly well suited for studies on morphological diversification [6-8]. Here, we show that post-translational modification of regulatory proteins provides a critical step in organ-shape formation. Our data reveal that the SUMO protease, HEARTBREAK (HTB), from Capsella rubella controls the activity of the key regulator of fruit development, INDEHISCENT (CrIND in C. rubella), via de-SUMOylation. This post-translational modification initiates a transduction pathway required to ensure precisely localized auxin biosynthesis, thereby facilitating anisotropic cell expansion to ultimately form the heart-shaped Capsella fruit. Therefore, although variation in the expression of key regulatory genes is known to be a primary driver in morphological evolution, our work demonstrates how other processes-such as post-translational modification of one such regulator-affects organ morphology.
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| 3. |
- Doyle, Siamsa, et al.
(författare)
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A role for the auxin precursor anthranilic acid in root gravitropism via regulation of PIN‐FORMED protein polarity and relocalisation in Arabidopsis
- 2019
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Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 223:3, s. 1420-1432
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Tidskriftsartikel (refereegranskat)abstract
- Distribution of auxin within plant tissues is of great importance for developmental plasticity, including root gravitropic growth. Auxin flow is directed by the subcellular polar distribution and dynamic relocalisation of auxin transporters such as the PIN‐FORMED (PIN) efflux carriers, which can be influenced by the main natural plant auxin indole‐3‐acetic acid (IAA). Anthranilic acid (AA) is an important early precursor of IAA and previously published studies with AA analogues have suggested that AA may also regulate PIN localisation.Using Arabidopsis thaliana as a model species, we studied an AA‐deficient mutant displaying agravitropic root growth, treated seedlings with AA and AA analogues and transformed lines to over‐produce AA while inhibiting its conversion to downstream IAA precursors.We showed that AA rescues root gravitropic growth in the AA‐deficient mutant at concentrations that do not rescue IAA levels. Overproduction of AA affects root gravitropism without affecting IAA levels. Treatments with, or deficiency in, AA result in defects in PIN polarity and gravistimulus‐induced PIN relocalisation in root cells.Our results revealed a previously unknown role for AA in the regulation of PIN subcellular localisation and dynamics involved in root gravitropism, which is independent of its better known role in IAA biosynthesis.
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| 4. |
- Grones, Peter, et al.
(författare)
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Fluctuating auxin response gradients determine pavement cell-shape acquisition
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117, s. 16027-16034
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Tidskriftsartikel (refereegranskat)abstract
- Puzzle-shaped pavement cells provide a powerful model system to investigate the cellular and subcellular processes underlying com- plex cell-shape determination in plants. To better understand pavement cell-shape acquisition and the role of auxin in this pro- cess, we focused on the spirals of young stomatal lineage ground cells of Arabidopsis leaf epidermis. The predictability of lobe forma- tion in these cells allowed us to demonstrate that the auxin response gradient forms within the cells of the spiral and fluctuates based on the particular stage of lobe development. We revealed that specific localization of auxin transporters at the different membranes of these young cells changes during the course of lobe formation, sug- gesting that these fluctuating auxin response gradients are orches- trated via auxin transport to control lobe formation and determine pavement cell shape.
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| 5. |
- Kushwah, Sunita, et al.
(författare)
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Arabidopsis XTH4 and XTH9 Contribute to Wood Cell Expansion and Secondary Wall Formation(1)([OPEN])
- 2020
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Ingår i: Plant Physiology. - : American Society of Plant Science. - 0032-0889 .- 1532-2548. ; 182:4, s. 1946-1965
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Tidskriftsartikel (refereegranskat)abstract
- Xyloglucan is the major hemicellulose of dicotyledon primary cell walls, affecting the load-bearing framework with the participation of xyloglucan endo-transglycosylase/hydrolases (XTHs). We used loss- and gain-of function approaches to study functions of XTH4 and XTH9 abundantly expressed in cambial regions during secondary growth of Arabidopsis (Arabidopsis thaliana). In secondarily thickened hypocotyls, these enzymes had positive effects on vessel element expansion and fiber intrusive growth. They also stimulated secondary wall thickening but reduced secondary xylem production. Cell wall analyses of inflorescence stems revealed changes in lignin, cellulose, and matrix sugar composition indicating an overall increase in secondary versus primary walls in mutants, indicative of higher xylem production compared with the wild type (since secondary walls were thinner). Intriguingly, the number of secondary cell wall layers compared with the wild type was increased in xth9 and reduced in xth4, whereas the double mutant xth4x9 displayed an intermediate number of layers. These changes correlated with specific Raman signals from the walls, indicating changes in lignin and cellulose. Secondary walls were affected also in the interfascicular fibers, where neither XTH4 nor XTH9 was expressed, indicating that these effects were indirect. Transcripts involved in secondary wall biosynthesis and cell wall integrity sensing, including THESEUS1 and WALL ASSOCIATED KINASE2, were highly induced in the mutants, indicating that deficiency in XTH4 and XTH9 triggers cell wall integrity signaling, which, we propose, stimulates xylem cell production and modulates secondary wall thickening. Prominent effects of XTH4 and XTH9 on secondary xylem support the hypothesis that altered xyloglucan affects wood properties both directly and via cell wall integrity sensing.
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| 6. |
- Majda, Mateusz, et al.
(författare)
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Elongation of wood fibers combines features of diffuse and tip growth
- 2021
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Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 232:2, s. 673-691
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Tidskriftsartikel (refereegranskat)abstract
- Xylem fibers are highly elongated cells that are key constituents of wood, play major physiological roles in plants, comprise an important terrestrial carbon reservoir, and thus have enormous ecological and economic importance. As they develop, from fusiform initials, their bodies remain the same length while their tips elongate and intrude into intercellular spaces.To elucidate mechanisms of tip elongation, we studied the cell wall along the length of isolated, elongating aspen xylem fibers and used computer simulations to predict the forces driving the intercellular space formation required for their growth.We found pectin matrix epitopes (JIM5, LM7) concentrated at the tips where cellulose microfibrils have transverse orientation, and xyloglucan epitopes (CCRC-M89, CCRC-M58) in fiber bodies where microfibrils are disordered. These features are accompanied by changes in cell wall thickness, indicating that while the cell wall elongates strictly at the tips, it is deposited all over fibers. Computer modeling revealed that the intercellular space formation needed for intrusive growth may only require targeted release of cell adhesion, which allows turgor pressure in neighboring fiber cells to ‘round’ the cells creating spaces.These characteristics show that xylem fibers’ elongation involves a distinct mechanism that combines features of both diffuse and tip growth.
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| 7. |
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| 8. |
- Majda, Mateusz, et al.
(författare)
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Mechanochemical Polarization of Contiguous Cell Walls Shapes Plant Pavement Cells
- 2017
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Ingår i: Developmental Cell. - : Elsevier BV. - 1534-5807 .- 1878-1551. ; 43:3, s. 4-304
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Tidskriftsartikel (refereegranskat)abstract
- The epidermis of aerial plant organs is thought to be limiting for growth, because it acts as a continuous load-bearing layer, resisting tension. Leaf epidermis contains jigsaw puzzle piece-shaped pavement cells whose shape has been proposed to be a result of subcellular variations in expansion rate that induce local buckling events. Paradoxically, such local compressive buckling should not occur given the tensile stresses across the epidermis. Using computational modeling, we show that the simplest scenario to explain pavement cell shapes within an epidermis under tension must involve mechanical wall heterogeneities across and along the anticlinal pavement cell walls between adjacent cells. Combining genetics, atomic force microscopy, and immunolabeling, we demonstrate that contiguous cell walls indeed exhibit hybrid mechanochemical properties. Such biochemical wall heterogeneities precede wall bending. Altogether, this provides a possible mechanism for the generation of complex plant cell shapes. Pavement cells in the leaf epidermis are multi-lobed like jigsaw puzzle pieces. Majda et al. provide evidence through in vivo analyses using atomic force microscopy and computational modeling that mechanical heterogeneities across and along anticlinal cell walls allow wall bending that contributes to lobe formation and these complex cell shapes.
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| 9. |
- Majda, Mateusz, et al.
(författare)
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The Role of Auxin in Cell Wall Expansion
- 2018
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 19
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Forskningsöversikt (refereegranskat)abstract
- Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition.
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| 10. |
- Majda, Mateusz
(författare)
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Visualization of Plant Cell Wall Epitopes Using Immunogold Labeling for Electron Microscopy
- 2019
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Ingår i: Bio-protocol. - 2331-8325. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Plant cell walls consist of different polysaccharides and structural proteins, which form a rigid layer located outside of the plasma membrane. The wall is also a very dynamic cell composite, which is characterized by complex polysaccharide interactions and various modifications during cell development. The visualization of cell wall components in situ is very challenging due to the small size of cell wall composites (nanometer scale), large diversity of the wall polysaccharides and their complex interactions. This protocol describes immunogold labeling of different cell wall epitopes for high-resolution transmission electron microscopy (TEM). It provides a detailed procedure for collection and preparation of plant material, ultra-thin sectioning, specimen labeling and contrasting. An immunolabeling procedure workflow was optimized to obtain high efficiency of carbohydrates labeling for high-resolution TEM. This method was applied to study plant cell wall characteristics in various plant tissues but could also be applied for other cell components in plant and animal tissues.
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