Faculty Opinions recommendation of Calcium participates in feedback regulation of the oscillating ROP1 Rho GTPase in pollen tubes.

2009 ◽  
Author(s):  
Geneviève Dupont
Keyword(s):  
Rho Gtpase ◽  
Feedback Regulation ◽  
Pollen Tubes

scholarly journals Localization of a Rho GTPase Implies a Role in Tip Growth and Movement of the Generative Cell in Pollen Tubes.

1996 ◽  
pp. 293-303 ◽  
Author(s):  
Y. Lin ◽  
Y. Wang ◽  
J. K. Zhu ◽  
Z. Yang
Keyword(s):  
Tip Growth ◽  
Rho Gtpase ◽  
Generative Cell ◽  
Pollen Tubes

scholarly journals Oscillatory ROP GTPase Activation Leads the Oscillatory Polarized Growth of Pollen Tubes

2005 ◽  
Vol 16 (11) ◽  
pp. 5385-5399 ◽  
Author(s):  
Jae-Ung Hwang ◽  
Ying Gu ◽  
Yong-Jik Lee ◽  
Zhenbiao Yang
Keyword(s):  
Gene Expression ◽  
Molecular Mechanisms ◽  
Tip Growth ◽  
Rho Gtpase ◽  
Cell Movement ◽  
Pollen Tubes ◽  
Common Mechanism ◽  
Rop Gtpase ◽  
Growth Oscillation ◽  
Gtpase Activation

Oscillation regulates a wide variety of processes ranging from chemotaxis in Dictyostelium through segmentation in vertebrate development to circadian rhythms. Most studies on the molecular mechanisms underlying oscillation have focused on processes requiring a rhythmic change in gene expression, which usually exhibit a periodicity of >10 min. Mechanisms that control oscillation with shorter periods (<10 min), presumably independent of gene expression changes, are poorly understood. Oscillatory pollen tube tip growth provides an excellent model to investigate such mechanisms. It is well established that ROP1, a Rho-like GTPase from plants, plays an essential role in polarized tip growth in pollen tubes. In this article, we demonstrate that tip-localized ROP1 GTPase activity oscillates in the same frequency with growth oscillation, and leads growth both spatially and temporally. Tip growth requires the coordinate action of two ROP1 downstream pathways that promote the accumulation of tip-localized Ca2+and actin microfilaments (F-actin), respectively. We show that the ROP1 activity oscillates in a similar phase with the apical F-actin but apparently ahead of tip-localized Ca2+. Furthermore, our observations support the hypothesis that the oscillation of tip-localized ROP activity and ROP-dependent tip growth in pollen tubes is modulated by the two temporally coordinated downstream pathways, an early F-actin assembly pathway and a delayed Ca2+gradient-forming pathway. To our knowledge, our report is the first to demonstrate the oscillation of Rho GTPase signaling, which may be a common mechanism underlying the oscillation of actin-dependent processes such as polar growth, cell movement, and chemotaxis.

scholarly journals Rho GTPase ROP1 Interactome Analysis Reveals Novel ROP1-Associated Pathways for Pollen Tube Polar Growth in Arabidopsis

2020 ◽  
Vol 21 (19) ◽  
pp. 7033
Author(s):  
Hui Li ◽  
Jinbo Hu ◽  
Jing Pang ◽  
Liangtao Zhao ◽  
Bing Yang ◽  
...  
Keyword(s):  
Cell Growth ◽  
Pollen Tube ◽  
Rho Gtpase ◽  
Ion Homeostasis ◽  
Pollen Tubes ◽  
Polar Growth ◽  
Cell Wall Modification ◽  
Polar Cell ◽  
Associated Proteins ◽  
Arabidopsis Pollen

ROP (Rho-like GTPases from plants) GTPases are polarly localized key regulators of polar growth in pollen tubes and other cells in plants. However, how ROP GTPases are regulated and how they control polar growth remains to be fully understood. To gain new insights into ROP-dependent mechanisms underlying polar cell growth, we characterized the interactome of ROP1 GTPase that controls Arabidopsis pollen tube (PT) tip growth, an extreme form of polar cell growth. We established an efficient method for culturing Arabidopsis pollen tubes in liquid medium, which was used for immunoprecipitation/mass spectrometry-based identification of ROP1-associated proteins. A total of 654 candidates were isolated from the ROP1 interactome in Arabidopsis pollen tubes, and GO (Gene Ontology) classification and pathway analysis revealed multiple uncharacterized ROP1-dependent processes including translation, cell wall modification, post transcriptional modification, and ion homeostasis, in addition to known ROP1-dependent pathways. The ROP1-interactome data was further supported by the co-expression of the candidate interactors in highly mature pollen with PT germination and growth defects being discovered in 25% (8/32) of the candidate mutant genes. Taken together, our work uncovers valuable information for the identification and functional elucidation of ROP-associated proteins in the regulation of polar growth, and provides a reliable reference to identify critical regulators of polar cell growth in the future.

scholarly journals Plasma membrane nano-organization specifies phosphoinositide effects on Rho-GTPases and actin dynamics in tobacco pollen tubes

2020 ◽  
Author(s):  
Marta Fratini ◽  
Praveen Krishnamoorthy ◽  
Irene Stenzel ◽  
Mara Riechmann ◽  
Kirsten Bacia ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Pollen Tubes ◽  
Actin Dynamics ◽  
Tobacco Pollen ◽  
Dual Distribution ◽  
Cytoskeletal Dynamics

AbstractPollen tube growth requires coordination of cytoskeletal dynamics and apical secretion. The regulatory phospholipid, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) is enriched in the subapical plasma membrane of pollen tubes and can influence both actin dynamics and secretion. How alternative PtdIns(4,5)P2-effects are specified is unclear. Spinning disc microscopy (SD) reveals dual distribution of a fluorescent PtdIns(4,5)P2-reporter in dynamic plasma membrane nanodomains vs. apparent diffuse membrane labelling, consistent with spatially distinct coexisting pools of PtdIns(4,5)P2. Several PI4P 5-kinases (PIP5Ks) can generate PtdIns(4,5)P2 in pollen tubes. Despite localizing to one membrane region, AtPIP5K2 and NtPIP5K6 display distinctive overexpression effects on cell morphologies, respectively related to altered actin dynamics or membrane trafficking. When analyzed by SD, AtPIP5K2-EYFP associated with nanodomains, whereas NtPIP5K6-EYFP localized diffusely. Chimeric AtPIP5K2 and NtPIP5K6 variants with reciprocally swapped membrane-associating domains evoked reciprocally shifted effects on cell morphology upon overexpression. Overall, PI4P 5-kinase variants targeted to nanodomains stabilized actin, suggesting a specific function of PtdIns(4,5)P2-nanodomains. A distinct role of nanodomain-associated AtPIP5K2 in actin regulation is further supported by proximity to and interaction with the Rho-GTPase NtRac5, and by functional interplay with elements of ROP-signalling. Plasma membrane nano-organization may thus aid the specification of PtdIns(4,5)P2-functions to coordinate cytoskeletal dynamics and secretion in pollen tubes.

Localization of a Rho GTPase Implies a Role in Tip Growth and Movement of the Generative Cell in Pollen Tubes

1996 ◽  
Vol 8 (2) ◽  
pp. 293 ◽  
Author(s):  
Yakang Lin ◽  
Yalai Wang ◽  
Jian-kang Zhu ◽  
Zhenbiao Yang
Keyword(s):  
Tip Growth ◽  
Rho Gtpase ◽  
Generative Cell ◽  
Pollen Tubes

scholarly journals Rap-afadin axis in control of Rho signaling and endothelial barrier recovery

2013 ◽  
Vol 24 (17) ◽  
pp. 2678-2688 ◽  
Author(s):  
Anna A. Birukova ◽  
Xinyong Tian ◽  
Yufeng Tian ◽  
Katherine Higginbotham ◽  
Konstantin G. Birukov
Keyword(s):  
Rho Gtpase ◽  
Physiological Mechanism ◽  
Adherens Junction ◽  
Feedback Regulation ◽  
Actin Stress Fiber ◽  
Nucleotide Exchange ◽  
Down Regulation ◽  
Negative Feedback Regulation ◽  
P120 Catenin ◽  
Rap1 Activation

Activation of the Rho GTPase pathway determines endothelial cell (EC) hyperpermeability after injurious stimuli. To date, feedback mechanisms of Rho down-regulation critical for barrier restoration remain poorly understood. We tested a hypothesis that Rho down-regulation and barrier recovery of agonist-stimulated ECs is mediated by the Ras family GTPase Rap1. Thrombin-induced EC permeability driven by rapid activation of the Rho GTPase pathway was followed by Src kinase–dependent phosphorylation of the Rap1-specific guanine nucleotide exchange factor (GEF) C3G, activation of Rap1, and initiation of EC barrier recovery. Knockdown experiments showed that Rap1 activation was essential for down-regulation of Rho signaling and actin stress fiber dissolution. Rap1 activation also enhanced interaction between adherens junction (AJ) proteins VE-cadherin and p120-catenin and stimulated AJ reannealing mediated by the Rap1 effector afadin. This mechanism also included Rap1-dependent membrane translocation of the Rac1-specific GEF Tiam1 and activation of Rac1-dependent peripheral cytoskeletal dynamics, leading to resealing of intercellular gaps. These data demonstrate that activation of the Rap1-afadin axis is a physiological mechanism driving restoration of barrier integrity in agonist-stimulated EC monolayers via negative-feedback regulation of Rho signaling, stimulation of actin peripheral dynamics, and reestablishment of cell–cell adhesive complexes.

scholarly journals ROP Gtpase–Dependent Dynamics of Tip-Localized F-Actin Controls Tip Growth in Pollen Tubes

2001 ◽  
Vol 152 (5) ◽  
pp. 1019-1032 ◽  
Author(s):  
Ying Fu ◽  
Guang Wu ◽  
Zhenbiao Yang
Keyword(s):  
Tip Growth ◽  
Fluorescent Protein ◽  
Rho Gtpase ◽  
Pollen Tubes ◽  
Actin Binding ◽  
Apical Region ◽  
Polar Growth ◽  
Actin Organization ◽  
Rop Gtpase ◽  
Rho Family

Tip-growing pollen tubes provide a useful model system to study polar growth. Although roles for tip-focused calcium gradient and tip-localized Rho-family GTPase in pollen tube growth is established, the existence and function of tip-localized F-actin have been controversial. Using the green fluorescent protein–tagged actin-binding domain of mouse talin, we found a dynamic form of tip-localized F-actin in tobacco pollen tubes, termed short actin bundles (SABs). The dynamics of SABs during polar growth in pollen tubes is regulated by Rop1At, a Rop GTPase belonging to the Rho family. When overexpressed, Rop1At transformed SAB into a network of fine filaments and induced a transverse actin band behind the tip, leading to depolarized growth. These changes were due to ectopic Rop1At localization to the apical region of the plasma membrane and were suppressed by guanine dissociation inhibitor overexpression, which removed ectopically localized Rop1At. Rop GTPase–activating protein (RopGAP1) overexpression, or Latrunculin B treatments, also recovered normal actin organization and tip growth in Rop1At-overexpressing tubes. Moreover, overexpression of RopGAP1 alone disrupted SABs and inhibited growth. Finally, SAB oscillates and appears at the tip before growth. Together, these results indicate that the dynamics of tip actin are essential for tip growth and provide the first direct evidence to link Rho GTPase to actin organization in controlling cell polarity and polar growth in plants.

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