Localized changes in apoplastic and cytoplasmic pH are associated with root hair development in Arabidopsis thaliana

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2925-2934 ◽  
Author(s):  
T.N. Bibikova ◽  
T. Jacob ◽  
I. Dahse ◽  
S. Gilroy
Keyword(s):  
Root Hair ◽  
Tip Growth ◽  
Root Hairs ◽  
Initiation Site ◽  
Cytoplasmic Ph ◽  
Apoplastic Ph ◽  
Initiation Process ◽  
Root Hair Formation ◽  
Root Hair Initiation ◽  
Hair Formation

Morphogenesis in plants is characterized by highly regulated cell enlargement. However, the mechanisms controlling and localizing regions of growth remain essentially unknown. Root hair formation involves the induction of a localized cell expansion in the lateral wall of a root epidermal cell. This expanded region then enters a second phase of localized growth called tip growth. Root hair formation therefore provides a model in which to study the cellular events involved in regulating localized growth in plants. Confocal ratio imaging of the pH of the cell wall revealed an acidification at the root hair initiation site. This acidification was present from the first morphological indications of localized growth, but not before, and was maintained to the point where the process of root hair initiation ceased and tip growth began. Preventing the wall acidification with pH buffers arrested the initiation process but growth resumed when the wall was returned to an acidic pH. Cytoplasmic pH was found to be elevated from approximately 7.3 to 7. 7 at the initiation site, and this elevation coincided with the acidification of the wall. Preventing the localized increase in cytoplasmic pH with 10 mM butyrate however did not inhibit either the wall acidification or the initiation process. In contrast, there was no detectable gradient in pH associated with the apex of tip growing root hairs, but both elevated apoplastic pH and butyrate treatment irreversibly inhibited the tip growth process. Thus the processes of tip growth and initiation of root hairs show differences in their pH requirements. These results highlight the role of localized control of apoplastic pH in the control of cell architecture and morphogenesis in plants.

scholarly journals AtRBOHC/RHD2 vesicular delivery to the apical plasma membrane domain during root hair development

2021 ◽  
Author(s):  
Lenka Kuběnová ◽  
Michaela Tichá ◽  
Jozef Šamaj ◽  
Miroslav Ovečka
Keyword(s):  
Plasma Membrane ◽  
Quantitative Analysis ◽  
Root Hair ◽  
Tip Growth ◽  
Root Hairs ◽  
Apical Plasma Membrane ◽  
Loss Of Function ◽  
Short Root ◽  
Early Endosomes ◽  
Root Hair Initiation

AbstractArabidopsis root hairs develop as long tubular extensions from the rootward pole of trichoblasts and exert polarized tip growth. The establishment and maintenance of root hair polarity is a complex process involving the local apical production of reactive oxygen species (ROS) generated by NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG PROTEIN C/ROOT HAIR DEFECTIVE 2 (AtRBOHC/RHD2). It has been shown that loss-of-function rhd2 mutants have short root hairs that are unable to elongate by tip growth, and this phenotype was fully complemented by GFP-RHD2 expressed under the RHD2 promoter. However, the spatiotemporal mechanism of AtRBOHC/RHD2 subcellular redistribution and delivery to the plasma membrane (PM) during root hair initiation and tip growth are still unclear. Here, we used advanced microscopy for detailed qualitative and quantitative analysis of vesicular compartments containing GFP-RHD2 and characterization of their movements in developing bulges and growing root hairs. These compartments, identified by an independent marker such as the trans-Golgi network (TGN), deliver GFP-RHD2 to the apical PM domain, the extent of which correlates with the stage of root hair formation. Movements of TGN/early endosomes, but not late endosomes, were affected in the bulging domains of the rhd2-1 mutant. Finally, we reveal that accumulation in the growing tip, docking, and incorporation of TGN compartments containing GFP-RHD2 to the apical PM of root hairs requires structural sterols. These results help clarify the mechanism of polarized AtRBOHC/RHD2 targeting, maintenance, and recycling at the apical PM domain, coordinated with different developmental stages of root hair initiation and growth.One-sentence summaryAdvanced microscopy and quantitative analysis of vesicular TGN compartments revealed that delivering GFP-RHD2 to the apical plasma membrane domains of developing bulges and growing root hairs requires structural sterols.

scholarly journals GTL1 is required for a robust root hair growth response to avoid nutrient overloading

2021 ◽  
Author(s):  
Michitaro Shibata ◽  
David S Favero ◽  
Ryu Takebayashi ◽  
Ayako Kawamura ◽  
Bart Rymen ◽  
...  
Keyword(s):  
Nutrient Availability ◽  
Root Hair ◽  
Hair Growth ◽  
Root Hairs ◽  
The Face ◽  
Hand Defects ◽  
Positive Regulators ◽  
Root Hair Formation ◽  
Root Hair Growth ◽  
Hair Formation

Root hair growth is tuned in response to the environment surrounding plants. While most of previous studies focused on the enhancement of root hair growth during nutrient starvation, few studies investigated the root hair response in the presence of excess nutrients. We report that the post-embryonic growth of wild-type Arabidopsis plants is strongly suppressed with increasing nutrient availability, particularly in the case of root hair growth. We further used gene expression profiling to analyze how excess nutrient availability affects root hair growth, and found that RHD6 subfamily genes, which are positive regulators of root hair growth, are down-regulated in this condition. On the other hand, defects in GTL1 and DF1, which are negative regulators of root hair growth, cause frail and swollen root hairs to form when excess nutrients are supplied. Additionally, we observed that the RHD6 subfamily genes are mis-expressed in gtl1-1 df1-1. Furthermore, overexpression of RSL4, an RHD6 subfamily gene, induces swollen root hairs in the face of a nutrient overload, while mutation of RSL4 in gtl1-1 df1-1 restore root hair swelling phenotype. In conclusion, our data suggest that GTL1 and DF1 prevent unnecessary root hair formation by repressing RSL4 under excess nutrient conditions.

EIN3 and RSL4 interfere with an MYB–bHLH–WD40 complex to mediate ethylene-induced ectopic root hair formation in Arabidopsis

2021 ◽  
Vol 118 (51) ◽  
pp. e2110004118
Author(s):  
Yuping Qiu ◽  
Ran Tao ◽  
Ying Feng ◽  
Zhina Xiao ◽  
Dan Zhang ◽  
...  
Keyword(s):  
Root Hair ◽  
Molecular Mechanisms ◽  
Protein Complexes ◽  
Root Hairs ◽  
Elongation Factor ◽  
Root Hair Development ◽  
Root Hair Formation ◽  
Hair Development ◽  
Transcriptional Complex ◽  
Hair Formation

The alternating cell specifications of root epidermis to form hair cells or nonhair cells in Arabidopsis are determined by the expression level of GL2, which is activated by an MYB–bHLH–WD40 (WER–GL3–TTG1) transcriptional complex. The phytohormone ethylene (ET) has a unique effect of inducing N-position epidermal cells to form root hairs. However, the molecular mechanisms underlying ET-induced ectopic root hair development remain enigmatic. Here, we show that ET promotes ectopic root hair formation through down-regulation of GL2 expression. ET-activated transcription factors EIN3 and its homolog EIL1 mediate this regulation. Molecular and biochemical analyses further revealed that EIN3 physically interacts with TTG1 and interferes with the interaction between TTG1 and GL3, resulting in reduced activation of GL2 by the WER–GL3–TTG1 complex. Furthermore, we found through genetic analysis that the master regulator of root hair elongation, RSL4, which is directly activated by EIN3, also participates in ET-induced ectopic root hair development. RSL4 negatively regulates the expression of GL2, likely through a mechanism similar to that of EIN3. Therefore, our work reveals that EIN3 may inhibit gene expression by affecting the formation of transcription-activating protein complexes and suggests an unexpected mutual inhibition between the hair elongation factor, RSL4, and the hair specification factor, GL2. Overall, this study provides a molecular framework for the integration of ET signaling and intrinsic root hair development pathway in modulating root epidermal cell specification.

Epidermal pattern formation in the root and shoot of Arabidopsis

2007 ◽  
Vol 35 (1) ◽  
pp. 146-148 ◽  
Author(s):  
S. Schellmann ◽  
M. Hülskamp ◽  
J. Uhrig
Keyword(s):  
Pattern Formation ◽  
Root Hair ◽  
Leaf Surface ◽  
Root Hairs ◽  
Model Systems ◽  
Trichome Formation ◽  
Root Hair Formation ◽  
Epidermal Patterning ◽  
Hair Formation

Root hair formation, stomata development on hypocotyls and trichome formation on leaves in Arabidopsis represent three model systems for epidermal patterning in plants that involve a common set of genes or corresponding homologues. The resulting pattern and the developmental readout are, however, strikingly different. Trichomes become regularly spaced on the leaf surface. Root hairs and stomata-bearing cells are formed in rows at specific locations with reference to the underlying cortex cells. In this review, we summarize the mechanistic similarities and discuss differences that might account for the different outcome of patterning in each system.

scholarly journals Root Hair Formation: F-Actin-Dependent Tip Growth Is Initiated by Local Assembly of Profilin-Supported F-Actin Meshworks Accumulated within Expansin-Enriched Bulges

2000 ◽  
Vol 227 (2) ◽  
pp. 618-632 ◽  
Author(s):  
František Baluška ◽  
Ján Salaj ◽  
Jaideep Mathur ◽  
Markus Braun ◽  
Fred Jasper ◽  
...  
Keyword(s):  
Root Hair ◽  
Tip Growth ◽  
Local Assembly ◽  
Root Hair Formation ◽  
Hair Formation

scholarly journals Distinct ROPGEFs successively drive polarization and outgrowth of root hairs

2019 ◽  
Author(s):  
Philipp Denninger ◽  
Anna Reichelt ◽  
Vanessa A. F. Schmidt ◽  
Dietmar G. Mehlhorn ◽  
Lisa Y. Asseck ◽  
...  
Keyword(s):  
Root Hair ◽  
Tip Growth ◽  
Ectopic Expression ◽  
Root Hairs ◽  
Cell Types ◽  
Cell Polarization ◽  
Cellular Growth ◽  
Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Root Hair Formation

SUMMARYRoot hairs are tubular protrusions of the root epidermis that significantly enlarge the exploitable soil volume in the rhizosphere. Trichoblasts, the cell type responsible for root hair formation, switch from cell elongation to tip growth through polarization of the growth machinery to a pre-defined root hair initiation domain (RHID) at the plasma membrane. The emergence of this polar domain resembles the establishment of cell polarity in other eukaryotic systems [1–3]. Rho-type GTPases of plants (ROPs) are among the first molecular determinants of the RHID [4, 5] and later play a central role in polar growth [6]. Numerous studies have elucidated mechanisms that position the RHID in the cell [7–9] or regulate ROP activity [10–18]. The molecular players that target ROPs to the RHID and initiate outgrowth, however, have not been identified. We dissected the timing of the growth machinery assembly in polarizing hair cells and found that positioning of molecular players and outgrowth are temporally separate processes that are each controlled by specific ROP guanine nucleotide exchange factor (GEFs). A functional analysis of trichoblast-specific GEFs revealed GEF3 to be required for normal ROP polarization and thus efficient root hair emergence, while GEF4 predominantly regulates subsequent tip growth. Ectopic expression of GEF3 induced the formation of spatially confined, ROP-recruiting domains in other cell types, demonstrating the role of GEF3 to serve as a membrane landmark during cell polarization. Our findings suggest that morphogenetic programs in plants employ distinct regulatory modules for the alignment and activation of the cellular growth machinery.

scholarly journals Ethylene signaling increases reactive oxygen species accumulation to drive root hair initiation in Arabidopsis thaliana

2021 ◽  
Author(s):  
Rachel Emily Martin ◽  
Eliana Marzol ◽  
Jose M Estevez ◽  
Gloria K Muday
Keyword(s):  
Reactive Oxygen Species ◽  
Hair Cells ◽  
Root Hair ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Ethylene Signaling ◽  
Ros Accumulation ◽  
Root Hair Formation ◽  
Root Hair Initiation ◽  
Hair Formation

Root hair initiation is a highly regulated aspect of root development. The plant hormone, ethylene, and its precursor, 1-amino-cyclopropane-1-carboxylic acid (ACC), induce formation and elongation of root hairs. We asked whether elevated ethylene induced root hair formation by increasing reactive oxygen species (ROS) synthesis in hair cells. Using confocal microscopy paired with redox biosensors and dyes, we demonstrated that treatments that elevate ethylene levels led to increased ROS accumulation in hair cells prior to root hair formation. In two ethylene-insensitive mutants, etr1-3 and ein3/eil1, there was no increase in root hair number or ROS accumulation. Conversely, etr1-7, a constitutive ethylene signaling receptor mutant, has increased root hair formation and ROS accumulation similar to ethylene-treated wild type seedlings. The rhd2-6 mutant, with a defect in the gene encoding a ROS synthesizing Respiratory Burst Oxidase Homolog C (RBOHC), showed impaired ethylene-dependent ROS synthesis and root hair formation and decreased RBOH enzyme activity compared to Col-0. To identify additional proteins that drive ROS induced root hair formation, we examined a time course root transcriptomic dataset examining Col-0 grown in the presence of ACC and identified PRX44 and other positively regulated transcripts that encode class III peroxidases (PRXs). The prx44-2 mutant has decreased root hair initiation and ROS accumulation when treated with ACC compared to Col-0 and pPRX44::GFP fluorescence is increased in response to ACC treatment. Together, these results support a model in which ethylene increases ROS accumulation through RBOHC and PRX44 to drive root hair formation.

scholarly journals Alternative Oxidase Inhibition Impairs Tobacco Root Development and Root Hair Formation

2021 ◽  
Vol 12 ◽  
Author(s):  
Yang Liu ◽  
Lu-Lu Yu ◽  
Ye Peng ◽  
Xin-Xin Geng ◽  
Fei Xu
Keyword(s):  
Gene Expression ◽  
Root Development ◽  
Transcriptome Analysis ◽  
Root Hair ◽  
Alternative Oxidase ◽  
Regulation Of Gene Expression ◽  
Main Root ◽  
Respiratory Pathway ◽  
Root Hair Formation ◽  
Hair Formation

Alternative oxidase (AOX) is the terminal oxidase of the mitochondrial respiratory electron transport chain in plant cells and is critical for the balance of mitochondrial hemostasis. In this study, the effect of inhibition of AOX with different concentrations of salicylhydroxamic acid (SHAM) on the tobacco root development was investigated. We show here that AOX inhibition significantly impaired the development of the main root and root hair formation of tobacco. The length of the main root of SHAM-treated tobacco was significantly shorter than that of the control, and no root hairs were formed after treatment with a concentration of 1 mM SHAM or more. The transcriptome analysis showed that AOX inhibition by 1 mM SHAM involved in the regulation of gene expression related to root architecture. A total of 5,855 differentially expressed genes (DEGs) were obtained by comparing SHAM-treated roots with control. Of these, the gene expression related to auxin biosynthesis and perception were significantly downregulated by 1 mM SHAM. Similarly, genes related to cell wall loosening, cell cycle, and root meristem growth factor 1 (RGF1) also showed downregulation on SHAM treatment. Moreover, combined with the results of physiological measurements, the transcriptome analysis demonstrated that AOX inhibition resulted in excessive accumulation of reactive oxygen species in roots, which further induced oxidative damage and cell apoptosis. It is worth noting that when indoleacetic acid (20 nM) and dimethylthiourea (10 mM) were added to the medium containing SHAM, the defects of tobacco root development were alleviated, but to a limited extent. Together, these findings indicated that AOX-mediated respiratory pathway plays a crucial role in the tobacco root development, including root hair formation.

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