A Mutation in MRH2 Kinesin Enhances the Root Hair Tip Growth Defect Caused by Constitutively Activated ROP2 Small GTPase in Arabidopsis

NOTCH plays essential roles in cell fate specification during embryonic development and in adult tissue maintenance. In keratinocytes, it is a key inducer of differentiation. ROCK, an effector of the small GTPase Rho, is also implicated in keratinocyte differentiation, and its inhibition efficiently potentiates immortalization of human keratinocytes and greatly improves survival of dissociated human pluripotent stem cells. However, the molecular basis for ROCK activation is not fully established in these contexts. Here we provide evidence that intracellular forms of NOTCH1 trigger the immediate activation of ROCK1 independent of its transcriptional activity, promoting differentiation and resulting in decreased clonogenicity of normal human keratinocytes. Knockdown of NOTCH1 abrogated ROCK1 activation and conferred sustained clonogenicity upon differentiation stimuli. Treatment with a ROCK inhibitor, Y-27632, or ROCK1 silencing substantially rescued the growth defect induced by activated NOTCH1. Furthermore, we revealed that impaired self-renewal of human induced pluripotent stem cells upon dissociation is, at least in part, attributable to NOTCH-dependent ROCK activation. Thus, the present study unveils a novel NOTCH-ROCK pathway critical for cellular differentiation and loss of self-renewal capacity in a subset of immature cells.

Download Full-text

Signaling in Pollen Tube Growth: Beyond the Tip of the Polarity Iceberg

Plants ◽

10.3390/plants8060156 ◽

2019 ◽

Vol 8 (6) ◽

pp. 156 ◽

Cited By ~ 4

Author(s):

Nolan Scheible ◽

Andrew McCubbin

Keyword(s):

Pollen Tube ◽

Signaling Pathways ◽

Pollen Tube Growth ◽

Tip Growth ◽

Holistic Approach ◽

Pollen Tubes ◽

Small Gtpase ◽

Tube Growth ◽

Concerted Action ◽

Current State

The coordinated growth of pollen tubes through floral tissues to deliver the sperm cells to the egg and facilitate fertilization is a highly regulated process critical to the Angiosperm life cycle. Studies suggest that the concerted action of a variety of signaling pathways underlies the rapid polarized tip growth exhibited by pollen tubes. Ca2+ and small GTPase-mediated pathways have emerged as major players in the regulation of pollen tube growth. Evidence suggests that these two signaling pathways not only integrate with one another but also with a variety of other important signaling events. As we continue to elucidate the mechanisms involved in pollen tube growth, there is a growing importance in taking a holistic approach to studying these pathways in order to truly understand how tip growth in pollen tubes is orchestrated and maintained. This review considers our current state of knowledge of Ca2+-mediated and GTPase signaling pathways in pollen tubes, how they may intersect with one another, and other signaling pathways involved. There will be a particular focus on recent reports that have extended our understanding in these areas.

Download Full-text

A Galacturonic Acid–Containing Xyloglucan Is Involved in Arabidopsis Root Hair Tip Growth

The Plant Cell ◽

10.1105/tpc.112.103390 ◽

2012 ◽

Vol 24 (11) ◽

pp. 4511-4524 ◽

Cited By ~ 49

Author(s):

Maria J. Peña ◽

Yingzhen Kong ◽

William S. York ◽

Malcolm A. O’Neill

Keyword(s):

Root Hair ◽

Galacturonic Acid ◽

Tip Growth ◽

Arabidopsis Root

Download Full-text

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

The Plant Cell ◽

10.1105/tpc.107.056119 ◽

2008 ◽

Vol 20 (2) ◽

pp. 367-380 ◽

Cited By ~ 138

Author(s):

Hiroaki Kusano ◽

Christa Testerink ◽

Joop E.M. Vermeer ◽

Tomohiko Tsuge ◽

Hiroaki Shimada ◽

...

Keyword(s):

Root Hair ◽

Tip Growth ◽

Phosphatidylinositol Phosphate

Download Full-text

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

10.1101/2021.09.13.460100 ◽

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.

Download Full-text