Microtubule Initiation from the Nuclear Surface Controls Cortical Microtubule Growth Polarity and Orientation in Arabidopsis thaliana

Abstract Background Cortical microtubules regulate cell expansion by determining cellulose microfibril orientation in the root apex of Arabidopsis thaliana. While the regulation of cell wall properties by cortical microtubules is well studied, the data on the influence of cell wall to cortical microtubule organization and stability remain scarce. Studies on cellulose biosynthesis mutants revealed that cortical microtubules depend on Cellulose Synthase A (CESA) function and/or cell expansion. Furthermore, it has been reported that cortical microtubules in cellulose-deficient mutants are hypersensitive to oryzalin. In this work, the persistence of cortical microtubules against anti-microtubule treatment was thoroughly studied in the roots of several cesa mutants, namely thanatos, mre1, any1, prc1-1 and rsw1, and the Cellulose Synthase Interacting 1 protein (csi1) mutant pom2-4. In addition, various treatments with drugs affecting cell expansion were performed on wild-type roots. Whole mount tubulin immunolabeling was applied in the above roots and observations were performed by confocal microscopy. Results Cortical microtubules in all mutants showed statistically significant increased persistence against anti-microtubule drugs, compared to those of the wild-type. Furthermore, to examine if the enhanced stability of cortical microtubules was due to reduced cellulose biosynthesis or to suppression of cell expansion, treatments of wild-type roots with 2,6-dichlorobenzonitrile (DCB) and Congo red were performed. After these treatments, cortical microtubules appeared more resistant to oryzalin, than in the control. Conclusions According to these findings, it may be concluded that inhibition of cell expansion, irrespective of the cause, results in increased microtubule stability in A. thaliana root. In addition, cell expansion does not only rely on cortical microtubule orientation but also plays a regulatory role in microtubule dynamics, as well. Various hypotheses may explain the increased cortical microtubule stability under decreased cell expansion such as the role of cell wall sensors and the presence of less dynamic cortical microtubules.

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FRA1 modulates cortical microtubule localization of CMU proteins

10.1101/760389 ◽

2019 ◽

Author(s):

Anindya Ganguly ◽

Chuanmei Zhu ◽

Weizu Chen ◽

Ram Dixit

Keyword(s):

Arabidopsis Thaliana ◽

Cell Wall ◽

Molecular Mechanisms ◽

Cortical Microtubule ◽

Cellulose Synthase ◽

Lateral Stability ◽

Cortical Microtubules ◽

Tail Region ◽

Opposing Effect ◽

Growth And Reproduction

ABSTRACTConstruction of the cell wall demands harmonized deposition of cellulose and matrix polysaccharides. Cortical microtubules orient the deposition of cellulose by guiding the trajectory of plasma membrane-embedded cellulose synthase complexes. Vesicles containing matrix polysaccharides are thought to be transported by the FRA1 kinesin to facilitate their secretion along cortical microtubules. The cortical microtubule cytoskeleton thus provides a platform to coordinate the delivery of cellulose and matrix polysaccharides, but the underlying molecular mechanisms remain unknown. Here, we show that the tail region of the FRA1 kinesin physically interacts with CMU proteins which are important for the microtubule-dependent guidance of cellulose synthase complexes. Interaction with CMUs did not affect microtubule binding or motility of the FRA1 kinesin but had an opposing effect on the cortical microtubule localization of CMU1 and CMU2 proteins, thus regulating the lateral stability of cortical microtubules. Phosphorylation of the FRA1 tail region by CKL6 inhibited binding to CMUs and consequently reversed the extent of cortical microtubule decoration by CMU1 and CMU2. Genetic experiments demonstrated the significance of this interaction to the growth and reproduction of Arabidopsis thaliana plants. We propose that modulation of CMU’s microtubule localization by FRA1 provides a mechanism to control the coordinated deposition of cellulose and matrix polysaccharides.

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Aurora B spatially regulates EB3 phosphorylation to coordinate daughter cell adhesion with cytokinesis

The Journal of Cell Biology ◽

10.1083/jcb.201301131 ◽

2013 ◽

Vol 201 (5) ◽

pp. 709-724 ◽

Cited By ~ 40

Author(s):

Jorge G. Ferreira ◽

António J. Pereira ◽

Anna Akhmanova ◽

Helder Maiato

Keyword(s):

Cell Adhesion ◽

Daughter Cell ◽

Cortical Microtubule ◽

Focal Adhesions ◽

Mitotic Exit ◽

Aurora B ◽

Microtubule Stability ◽

Spatiotemporal Regulation ◽

Cytoskeleton Remodeling ◽

Microtubule Growth

During mitosis, human cells round up, decreasing their adhesion to extracellular substrates. This must be quickly reestablished by poorly understood cytoskeleton remodeling mechanisms that prevent detachment from epithelia, while ensuring the successful completion of cytokinesis. Here we show that the microtubule end-binding (EB) proteins EB1 and EB3 play temporally distinct roles throughout cell division. Whereas EB1 was involved in spindle orientation before anaphase, EB3 was required for stabilization of focal adhesions and coordinated daughter cell spreading during mitotic exit. Additionally, EB3 promoted midbody microtubule stability and, consequently, midbody stabilization necessary for efficient cytokinesis. Importantly, daughter cell adhesion and cytokinesis completion were spatially regulated by distinct states of EB3 phosphorylation on serine 176 by Aurora B. This EB3 phosphorylation was enriched at the midbody and shown to control cortical microtubule growth. These findings uncover differential roles of EB proteins and explain the importance of an Aurora B phosphorylation gradient for the spatiotemporal regulation of microtubule function during mitotic exit and cytokinesis.

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Molecular genetic analysis of left–right handedness in plants

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2002.1088 ◽

2002 ◽

Vol 357 (1422) ◽

pp. 799-808 ◽

Cited By ~ 83

Author(s):

Takashi Hashimoto

Keyword(s):

Arabidopsis Thaliana ◽

Genetic Analysis ◽

Molecular Genetic ◽

Cortical Microtubule ◽

Molecular Genetic Analysis ◽

Left Handed ◽

Helical Growth ◽

Molecular Components ◽

Axial Organs

Handedness in plant growth may be most familiar to us when we think of tendrils or twining plants, which generally form consistent right– or left–handed helices as they climb. The petals of several species are sometimes arranged like fan blades that twist in the same direction. Another less conspicuous example is ‘circumnutation’, the oscillating growth of axial organs, which alternates between a clockwise and an anti–clockwise direction. To unravel molecular components and cellular determinants of handedness, we screened Arabidopsis thaliana seedlings for helical growth mutants with fixed handedness. Recessive spiral1 and spiral2 mutants show right–handed helical growth in roots, hypocotyls, petioles and petals; semi–dominant lefty1 and lefty2 mutants show opposite left–handed growth in these organs. lefty mutations are epistatic to spiral mutations. Arabidopsis helical growth mutants with fixed handedness may be impaired in certain aspects of cortical microtubule functions, and characterization of the mutated genes should lead us to a better understanding of how microtubules function in left–right handedness in plants.

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iDePP: a genetically encoded system for the inducible depletion of PI(4,5)P2 in Arabidopsis thaliana

10.1101/2020.05.13.091470 ◽

2020 ◽

Cited By ~ 1

Author(s):

Mehdi Doumane ◽

Léia Colin ◽

Alexis Lebecq ◽

Aurélie Fangain ◽

Joseph Bareille ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Plasma Membrane ◽

Protein Localization ◽

Cortical Microtubule ◽

Plant Cells ◽

Actin Dynamics ◽

Animal Cells ◽

Compensatory Mechanisms ◽

Microtubule Organization ◽

Membrane Contact Sites

ABSTRACTPhosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a low abundant lipid present at the plasma membrane of eukaryotic cells. Extensive studies in animal cells revealed the pleiotropic functions of PI(4,5)P2. In plant cells, PI(4,5)P2 is involved in various cellular processes including the regulation of cell polarity and tip growth, clathrin-mediated endocytosis, polar auxin transport, actin dynamics or membrane-contact sites. To date, most studies investigating the role of PI(4,5)P2 in plants have relied on mutants lacking enzymes responsible for PI(4,5)P2 synthesis and degradation. However, such genetic perturbations only allow steady-state analysis of plants undergoing their life cycle in PI(4,5)P2 deficient conditions and the corresponding mutants are likely to induce a range of non-causal (untargeted) effects driven by compensatory mechanisms. In addition, there are no small molecule inhibitors that are available in plants to specifically block the production of this lipid. Thus, there is currently no system to fine tune PI(4,5)P2 content in plant cells. Here we report a genetically encoded and inducible synthetic system, iDePP (Inducible Depletion of PI(4,5)P2 in Plants), that efficiently removes PI(4,5)P2 from the plasma membrane in different organs of Arabidopsis thaliana, including root meristem, root hair and shoot apical meristem. We show that iDePP allows the inducible depletion of PI(4,5)P2 in less than three hours. Using this strategy, we reveal that PI(4,5)P2 is critical for cortical microtubule organization. Together, we propose that iDePP is a simple and efficient genetic tool to test the importance of PI(4,5)P2 in given cellular or developmental responses but also to evaluate the importance of this lipid in protein localization.Research OrganismA. thaliana

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