scholarly journals Spatial differences in stoichiometry of EGR phosphatase and Microtubule-Associated Stress Protein 1 control root meristem activity during drought stress.

2021 ◽  
Author(s):  
Toshisagba Longkumer ◽  
Chih-Yun Chen ◽  
Marco Biancucci ◽  
Bhaskara Govinal Badiger ◽  
Paul E. Verslues
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Cell Expansion ◽  
Growth Regulation ◽  
Root Meristem ◽  
Stress Protein ◽  
Root Cell ◽  
Root Cortex ◽  
Meristem Cell ◽  
Meristem Size

During moderate severity drought and low water potential (Ψw) stress, poorly understood signaling mechanisms restrict both meristem cell division and subsequent cell expansion. We found that the Clade E Growth-Regulating 2 (EGR2) protein phosphatase and Microtubule Associated Stress Protein 1 (MASP1) differed in their stoichiometry of expression across the root meristem and had opposing effects on root meristem activity at low Ψw. Ectopic MASP1 or EGR expression increased or decreased, respectively, root meristem size and root elongation during low Ψw stress. This, along with the ability of phosphomimic MASP1 to overcome EGR suppression of root meristem size and observation that ectopic EGR expression had no effect on unstressed plants, indicated that during low Ψw EGR activation and attenuation of MASP1 phosphorylation in their overlapping zone of expression determines root meristem size and activity. Ectopic EGR expression also decreased root cell size at low Ψw. Conversely, both the egr1-1egr2-1 and egr1-1egr2-1masp1-1 mutants had similarly increased root cell size; but, only egr1-1egr2-1 had increased cell division. These observations demonstrated that EGRs affect meristem activity via MASP1 but affect cell expansion via other mechanisms. Interestingly, EGR2 was highly expressed in the root cortex, a cell type important for growth regulation and environmental response.

scholarly journals ABA represses TOR and root meristem activity through nuclear exit of the SnRK1 kinase

2021 ◽  
Author(s):  
Borja Belda-Palazon ◽  
Monica Costa ◽  
Tom Beeckman ◽  
Filip Rolland ◽  
Elena Baena-Gonzalez
Keyword(s):  
Cell Proliferation ◽  
Nuclear Export ◽  
Growth Regulation ◽  
Root Meristem ◽  
Plant Tolerance ◽  
Proliferation Zone ◽  
Meristem Size ◽  
Main Driver ◽  
Root Meristematic Cells ◽  
Underlying Mechanisms

The phytohormone abscisic acid (ABA) promotes plant tolerance to major stresses like drought, partly by modulating plant growth and development. However, the underlying mechanisms are poorly understood. Here, we show that cell proliferation in the Arabidopsis thaliana root meristem is controlled by the interplay between three kinases, SNF1-RELATED KINASE 2 (SnRK2), the main driver of ABA signaling, the SnRK1 energy sensor, and the growth-promoting TARGET OF RAPAMYCIN (TOR) kinase. Under favorable conditions, the SnRK1α1 catalytic subunit is enriched in the nuclei of root meristematic cells and this is accompanied by normal cell proliferation and meristem size. Depletion of SnRK2s in a snrk2.2 snrk2.3 double mutant causes constitutive cytoplasmic localization of SnRK1α1 and a reduction in meristem size, suggesting that, under non-stress conditions, SnRK2s enable growth by retaining SnRK1α1 in the nucleus. In response to elevated ABA levels, SnRK1α1 translocates to the cytoplasm and this is accompanied by inhibition of TOR, decreased cell proliferation and meristem size. Blocking nuclear export with leptomycin B abrogates ABA-driven SnRK1α1 relocalization to the cytoplasm and the inhibition of TOR. Fusion of SnRK1α1 to an SV40 nuclear localization signal leads to defective TOR repression in response to ABA, demonstrating that SnRK1α1 nuclear exit is a premise for this repression. Finally, the SnRK2-dependent changes in SnRK1α1 subcellular localization are specific to the proliferation zone of the meristem, underscoring the relevance of this mechanism for growth regulation.

Nickel effect on root-meristem cell division in Plantago lanceolata (Plantaginaceae) seedlings

2017 ◽  
Vol 65 (5) ◽  
pp. 446 ◽  
Author(s):  
Dolja Pavlova
Keyword(s):  
Cell Division ◽  
Mitotic Index ◽  
Root Meristem ◽  
Plantago Lanceolata ◽  
Nuclear Material ◽  
Root Tip ◽  
Dependent Manner ◽  
Meristem Cell ◽  
Anaphase Bridges ◽  
Tip Cells

The toxic effect of nickel (Ni) on cell division on root-meristem cells in seedlings of Plantago lanceolata L. was studied and compared. Seed material was collected from serpentine and non-serpentine populations of the species distributed in the Rhodope Mountains, Bulgaria. The root-tip meristem cells of germinated seeds were treated with different solutions of 0.01, 0.025, 0.05, 0.1 mM Ni as NiSO4 6H2O with distilled water for 24 h and 48 h respectively. The mitotic index decreased when Ni concentrations and exposure time increased in both type of samples. Significant differences in the mitotic indexes were found between the controls and the roots treated with Ni. The mitotic index was higher in root-meristem cells of serpentine seedlings. C-mitosis, anaphase bridges, chromosome stickiness, laggards and extrusion of nuclear material into the cytoplasm were observed in the root-tip cells treated with Ni. The percentage of aberrations generally increased in a concentration- and time-dependent manner. The percentage of the extruded nuclei was higher in cells treated with 0.05 and 0.1 mM Ni. It can be concluded that P. lanceolata seedlings on serpentine can tolerate higher Ni concentrations than can non-serpentine seedlings.

Root development in Arabidopsis: four mutants with dramatically altered root morphogenesis

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 57-70 ◽  
Author(s):  
P.N. Benfey ◽  
P.J. Linstead ◽  
K. Roberts ◽  
J.W. Schiefelbein ◽  
M.T. Hauser ◽  
...  
Keyword(s):  
Root Growth ◽  
Root Development ◽  
Cell Expansion ◽  
Root Cell ◽  
Short Root ◽  
Root Cortex ◽  
Specific Effects ◽  
Cortex Cell ◽  
Cell Layers ◽  
Root Morphogenesis

A genetic analysis of root development in Arabidopsis thaliana has identified mutants that have abnormal morphogenesis. Four of these root morphogenesis mutants show dramatic alterations in post-embryonic root development. The short-root mutation results in a change from indeterminate to determinate root growth and the loss of internal root cell layers. The cobra and lion's tail mutations cause abnormal root cell expansion which is conditional upon the rate of root growth. Expansion is greatest in the epidermal cells in cobra and in the stele cells in lion's tail. The sabre mutation causes abnormal cell expansion that is greatest in the root cortex cell layer and is independent of the root growth rate. The tissue-specific effects of these mutations were characterized with monoclonal antibodies and a transgenic marker line. Genetic combinations of the four mutants have provided insight into the regulation of growth and cell shape during Arabidopsis root development.

scholarly journals Endocytic Trafficking Promotes Vacuolar Enlargements for Fast Cell Expansion Rates in Plants

2021 ◽  
Author(s):  
Kai Duenser ◽  
Maria Schoeller ◽  
Christian Loefke ◽  
Nannan Xiao ◽  
Barbora Parizkova ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Cell Size ◽  
Plant Cell ◽  
Cell Expansion ◽  
Plant Cells ◽  
Root Cell ◽  
Endocytic Trafficking ◽  
Size Determination ◽  
Space Filling

The vacuole has a space-filling function, allowing a particularly rapid plant cell expansion with very little increase in cytosolic content (Loefke et al., 2015; Scheuring et al., 2016; Duenser et al., 2019). Despite its importance for cell size determination in plants, very little is known about the mechanisms that define vacuolar size. Here we show that the cellular and vacuolar size expansions are coordinated. By developing a pharmacological tool, we enabled the investigation of membrane delivery to the vacuole during cellular expansion. Counterintuitively, our data reveal that endocytic trafficking from the plasma membrane to the vacuole is enhanced in the course of rapid root cell expansion. While this "compromise" mechanism may theoretically at first decelerate cell surface enlargements, it fuels vacuolar expansion and, thereby, ensures the coordinated augmentation of vacuolar occupancy in dynamically expanding plant cells.

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