The Arabidopsis Phosphatidylinositol Phosphate 5-Kinase PIP5K3 Is a Key Regulator of Root Hair Tip Growth

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.

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Molecular Mechanisms Regulating Root Hair Tip Growth: A Comparison with Pollen Tubes

Pollen Tip Growth ◽

10.1007/978-3-319-56645-0_9 ◽

2017 ◽

pp. 167-243 ◽

Cited By ~ 5

Author(s):

Sébastjen Schoenaers ◽

Daria Balcerowicz ◽

Kris Vissenberg

Keyword(s):

Root Hair ◽

Molecular Mechanisms ◽

Tip Growth ◽

Pollen Tubes

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Functional Characterization of fer-ts, a Temperature-Sensitive FERONIA Mutant Allele That Alters Root Hair Growth

10.1101/2020.05.27.119891 ◽

2020 ◽

Author(s):

Daewon Kim ◽

Jiyuan Yang ◽

Fangwei Gu ◽

Sung Jin Park ◽

Jonathon Combs ◽

...

Keyword(s):

Root Hair ◽

Plasma Membranes ◽

Tip Growth ◽

Elevated Temperatures ◽

Functional Characterization ◽

Root Hairs ◽

Temperature Sensitive ◽

Genetic Screens ◽

Binding Domains ◽

Cellular Components

ABSTRACTIn plants, root hairs undergo a highly-polarized form of cell expansion called tip-growth, in which cell wall deposition is restricted to the root hair apex. In order to identify essential cellular components that might have been missed in earlier genetic screens we identified conditional temperature sensitive (ts) root hair mutants by EMS mutagenesis. Here we describe one of these mutants, fer-ts (feronia-temperature sensitive). Mutant fer-ts seedlings grew normally at normal temperatures (20°C), but failed to form root hairs at elevated temperatures (30°C). Map based-cloning and whole genome sequencing revealed that fer-ts resulted from a G41S substitution in the extracellular domain of FERONIA (FER). A functional fluorescent fusion of FER containing the fer-ts mutation localized to plasma membranes, but was subject to enhanced protein turnover at elevated temperatures. While tip-growth was rapidly inhibited by addition of RALF1 peptides in both wild-type and fer-ts mutants at normal temperatures, root elongation of fer-ts seedlings was resistant to added RALF1 peptide at elevated temperatures. Additionally, at elevated temperatures fer-ts seedlings displayed altered ROS accumulation upon auxin treatment and phenocopied constitutive fer mutant responses to a variety of plant hormone treatments. Molecular modeling and sequence comparison with other CrRLK1L receptor family members revealed that the mutated glycine in fer-ts is highly conserved, but is not located in the recently characterized RALF23 and LORELI-LIKE-GLYCOPROTEIN (LLG2) binding domains, perhaps suggesting that fer-ts phenotypes may not be directly due to loss of binding to RALF1 peptides.

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