Skip to main content
NCBI home page
The Plant Cell logoLink to The Plant Cell
. 1999 Sep;11(9):1731–1742. doi: 10.1105/tpc.11.9.1731

Control of pollen tube tip growth by a Rop GTPase-dependent pathway that leads to tip-localized calcium influx.

H Li 1, Y Lin 1, R M Heath 1, M X Zhu 1, Z Yang 1
PMCID: PMC144310  PMID: 10488239

Abstract

We have shown that Rop1At, a pollen-specific Rop GTPase that is a member of the Rho family of small GTP binding proteins, acts as a key molecular switch controlling tip growth in Arabidopsis pollen tubes. Pollen-specific expression of constitutively active rop1at mutants induced isotropic growth of pollen tubes. Overexpression of wild-type Arabidopsis Rop1At led to ectopic accumulation of Rop1At in the plasma membrane at the tip and caused depolarization of pollen tube growth, which was less severe than that induced by the constitutively active rop1at. These results indicate that both Rop1At signaling and polar localization are critical for controlling the site of tip growth. Dominant negative rop1at mutants or antisense rop1at RNA inhibited tube growth at 0.5 mM extracellular Ca(2+), but growth inhibition was reversed by higher extracellular Ca(2+). Injection of anti-Rop antibodies disrupted the tip-focused intracellular Ca(2+) gradient known to be crucial for tip growth. These studies provide strong evidence for a Rop GTPase-dependent tip growth pathway that couples the control of growth sites with the rate of tip growth through the regulation of tip-localized extracellular Ca(2+) influxes and formation of the tip-high intracellular Ca(2+) gradient in pollen tubes.

Full Text

The Full Text of this article is available as a PDF (866.2 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bedinger P. The remarkable biology of pollen. Plant Cell. 1992 Aug;4(8):879–887. doi: 10.1105/tpc.4.8.879. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bibikova T. N., Zhigilei A., Gilroy S. Root hair growth in Arabidopsis thaliana is directed by calcium and an endogenous polarity. Planta. 1997 Dec;203(4):495–505. doi: 10.1007/s004250050219. [DOI] [PubMed] [Google Scholar]
  3. Chant J., Stowers L. GTPase cascades choreographing cellular behavior: movement, morphogenesis, and more. Cell. 1995 Apr 7;81(1):1–4. doi: 10.1016/0092-8674(95)90363-1. [DOI] [PubMed] [Google Scholar]
  4. Delmer D. P., Pear J. R., Andrawis A., Stalker D. M. Genes encoding small GTP-binding proteins analogous to mammalian rac are preferentially expressed in developing cotton fibers. Mol Gen Genet. 1995 Jul 22;248(1):43–51. doi: 10.1007/BF02456612. [DOI] [PubMed] [Google Scholar]
  5. Drubin D. G., Nelson W. J. Origins of cell polarity. Cell. 1996 Feb 9;84(3):335–344. doi: 10.1016/s0092-8674(00)81278-7. [DOI] [PubMed] [Google Scholar]
  6. Garrill A., Jackson S. L., Lew R. R., Heath I. B. Ion channel activity and tip growth: tip-localized stretch-activated channels generate an essential Ca2+ gradient in the oomycete Saprolegnia ferax. Eur J Cell Biol. 1993 Apr;60(2):358–365. [PubMed] [Google Scholar]
  7. Hall A. Rho GTPases and the actin cytoskeleton. Science. 1998 Jan 23;279(5350):509–514. doi: 10.1126/science.279.5350.509. [DOI] [PubMed] [Google Scholar]
  8. Haseloff J., Siemering K. R., Prasher D. C., Hodge S. Removal of a cryptic intron and subcellular localization of green fluorescent protein are required to mark transgenic Arabidopsis plants brightly. Proc Natl Acad Sci U S A. 1997 Mar 18;94(6):2122–2127. doi: 10.1073/pnas.94.6.2122. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Holdaway-Clarke T. L., Feijo J. A., Hackett G. R., Kunkel J. G., Hepler P. K. Pollen Tube Growth and the Intracellular Cytosolic Calcium Gradient Oscillate in Phase while Extracellular Calcium Influx Is Delayed. Plant Cell. 1997 Nov;9(11):1999–2010. doi: 10.1105/tpc.9.11.1999. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Kost B., Lemichez E., Spielhofer P., Hong Y., Tolias K., Carpenter C., Chua N. H. Rac homologues and compartmentalized phosphatidylinositol 4, 5-bisphosphate act in a common pathway to regulate polar pollen tube growth. J Cell Biol. 1999 Apr 19;145(2):317–330. doi: 10.1083/jcb.145.2.317. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Kuhn T. B., Williams C. V., Dou P., Kater S. B. Laminin directs growth cone navigation via two temporally and functionally distinct calcium signals. J Neurosci. 1998 Jan 1;18(1):184–194. doi: 10.1523/JNEUROSCI.18-01-00184.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Lee A., Wong S. T., Gallagher D., Li B., Storm D. R., Scheuer T., Catterall W. A. Ca2+/calmodulin binds to and modulates P/Q-type calcium channels. Nature. 1999 May 13;399(6732):155–159. doi: 10.1038/20194. [DOI] [PubMed] [Google Scholar]
  13. Li H., Wu G., Ware D., Davis K. R., Yang Z. Arabidopsis Rho-related GTPases: differential gene expression in pollen and polar localization in fission yeast. Plant Physiol. 1998 Oct;118(2):407–417. doi: 10.1104/pp.118.2.407. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Lin Y., Wang Y., Zhu J. K., Yang Z. Localization of a Rho GTPase Implies a Role in Tip Growth and Movement of the Generative Cell in Pollen Tubes. Plant Cell. 1996 Feb;8(2):293–303. doi: 10.1105/tpc.8.2.293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Lin Y., Yang Z. Inhibition of Pollen Tube Elongation by Microinjected Anti-Rop1Ps Antibodies Suggests a Crucial Role for Rho-Type GTPases in the Control of Tip Growth. Plant Cell. 1997 Sep;9(9):1647–1659. doi: 10.1105/tpc.9.9.1647. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Luo L., Liao Y. J., Jan L. Y., Jan Y. N. Distinct morphogenetic functions of similar small GTPases: Drosophila Drac1 is involved in axonal outgrowth and myoblast fusion. Genes Dev. 1994 Aug 1;8(15):1787–1802. doi: 10.1101/gad.8.15.1787. [DOI] [PubMed] [Google Scholar]
  17. Malho R., Read N. D., Trewavas A. J., Pais M. S. Calcium Channel Activity during Pollen Tube Growth and Reorientation. Plant Cell. 1995 Aug;7(8):1173–1184. doi: 10.1105/tpc.7.8.1173. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Malho R., Trewavas A. J. Localized Apical Increases of Cytosolic Free Calcium Control Pollen Tube Orientation. Plant Cell. 1996 Nov;8(11):1935–1949. doi: 10.1105/tpc.8.11.1935. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Messerli M., Robinson K. R. Tip localized Ca2+ pulses are coincident with peak pulsatile growth rates in pollen tubes of Lilium longiflorum. J Cell Sci. 1997 Jun;110(Pt 11):1269–1278. doi: 10.1242/jcs.110.11.1269. [DOI] [PubMed] [Google Scholar]
  20. Moutinho A, Trewavas AJ, Malho R. Relocation of a Ca2+-dependent protein kinase activity during pollen tube reorientation . Plant Cell. 1998 Sep;10(9):1499–1510. doi: 10.1105/tpc.10.9.1499. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Pierson E. S., Miller D. D., Callaham D. A., Shipley A. M., Rivers B. A., Cresti M., Hepler P. K. Pollen tube growth is coupled to the extracellular calcium ion flux and the intracellular calcium gradient: effect of BAPTA-type buffers and hypertonic media. Plant Cell. 1994 Dec;6(12):1815–1828. doi: 10.1105/tpc.6.12.1815. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Pierson E. S., Miller D. D., Callaham D. A., van Aken J., Hackett G., Hepler P. K. Tip-localized calcium entry fluctuates during pollen tube growth. Dev Biol. 1996 Feb 25;174(1):160–173. doi: 10.1006/dbio.1996.0060. [DOI] [PubMed] [Google Scholar]
  24. Ridley A. J., Hall A. The small GTP-binding protein rho regulates the assembly of focal adhesions and actin stress fibers in response to growth factors. Cell. 1992 Aug 7;70(3):389–399. doi: 10.1016/0092-8674(92)90163-7. [DOI] [PubMed] [Google Scholar]
  25. Ridley A. J., Paterson H. F., Johnston C. L., Diekmann D., Hall A. The small GTP-binding protein rac regulates growth factor-induced membrane ruffling. Cell. 1992 Aug 7;70(3):401–410. doi: 10.1016/0092-8674(92)90164-8. [DOI] [PubMed] [Google Scholar]
  26. Ridley A. J. Rho: theme and variations. Curr Biol. 1996 Oct 1;6(10):1256–1264. doi: 10.1016/s0960-9822(02)70711-2. [DOI] [PubMed] [Google Scholar]
  27. Roy SJ, Holdaway-Clarke TL, Hackett GR, Kunkel JG, Lord EM, Hepler PK. Uncoupling secretion and tip growth in lily pollen tubes: evidence for the role of calcium in exocytosis. Plant J. 1999 Aug;19(4):379–386. doi: 10.1046/j.1365-313x.1999.00515.x. [DOI] [PubMed] [Google Scholar]
  28. Scharenberg A. M., Kinet J. P. PtdIns-3,4,5-P3: a regulatory nexus between tyrosine kinases and sustained calcium signals. Cell. 1998 Jul 10;94(1):5–8. doi: 10.1016/s0092-8674(00)81214-3. [DOI] [PubMed] [Google Scholar]
  29. Silver R. A., Lamb A. G., Bolsover S. R. Calcium hotspots caused by L-channel clustering promote morphological changes in neuronal growth cones. Nature. 1990 Feb 22;343(6260):751–754. doi: 10.1038/343751a0. [DOI] [PubMed] [Google Scholar]
  30. Twell D., Yamaguchi J., Wing R. A., Ushiba J., McCormick S. Promoter analysis of genes that are coordinately expressed during pollen development reveals pollen-specific enhancer sequences and shared regulatory elements. Genes Dev. 1991 Mar;5(3):496–507. doi: 10.1101/gad.5.3.496. [DOI] [PubMed] [Google Scholar]
  31. Winge P., Brembu T., Bones A. M. Cloning and characterization of rac-like cDNAs from Arabidopsis thaliana. Plant Mol Biol. 1997 Nov;35(4):483–495. doi: 10.1023/a:1005804508902. [DOI] [PubMed] [Google Scholar]
  32. Yang Z. Signaling tip growth in plants. Curr Opin Plant Biol. 1998 Dec;1(6):525–530. doi: 10.1016/s1369-5266(98)80046-0. [DOI] [PubMed] [Google Scholar]
  33. Yang Z., Watson J. C. Molecular cloning and characterization of rho, a ras-related small GTP-binding protein from the garden pea. Proc Natl Acad Sci U S A. 1993 Sep 15;90(18):8732–8736. doi: 10.1073/pnas.90.18.8732. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Plant Cell are provided here courtesy of Oxford University Press

RESOURCES