Plant and Cell Physiology, 2004, Vol. 45, No. 5 535-542
© 2004 Oxford University Press
Secretion in Unicellular Marine Phytoplankton: Demonstration of Regulated Exocytosis in Phaeocystis globosa
1 Biomedical Engineering Program, Department of Chemical Engineering, FAMU/FSU, Tallahassee, FL 32310, U.S.A.
2 The Institute for Systems Biology, Seattle, WA 98103, U.S.A.
3 Department of Bioengineering and Friday Harbor Labs, University of Washington, Seattle, WA 98195, U.S.A.
Almost half of the global photosynthetic activity is carried out in the ocean. During blooms, Phaeocystis can fix CO2 at rates up to 40 g C m–2 month–1. Most of this carbon is released as polysaccharides. However, the cellular mechanism whereby this huge amount of organic material is exported into the seawater remains unknown. A vaguely defined process of "exudation" is believed responsible for the release of these biopolymers. Here we report the first demonstration that Phaeocystis globosa does not "exude", but secretes microscopic gels. Secretion is stimulated by blue light (
= 470±20 nm), and it is transduced by a characteristic intracellular Ca2+ signal that precedes degranulation. The polysaccharides that form the matrix of these gels remain in condensed phase while stored in secretory vesicles. Upon exocytosis, the exopolymer matrix undergoes a characteristic phase transition accompanied by extensive swelling resulting in the formation of microscopic hydrated gels. Owing to their tangled topology, once released into the seawater, the polymers that make these gels can reptate (axially diffuse), interpenetrate neighboring gels, and anneal them together forming massive mucilage accumulations that are characteristic of Phaeocystis blooms. These gel masses can supply a rich source of microbial substrates, disperse in the seawater, and/or eventually sediment to the ocean floor.
4 Corresponding author: E-mail, verdugo{at}u.washington.edu; Fax, +1-206-543-1273.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Perez-Vilar Mucin Granule Intraluminal Organization Am. J. Respir. Cell Mol. Biol., February 1, 2007; 36(2): 183 - 190. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Perez-Vilar, R. Mabolo, C. T. McVaugh, C. R. Bertozzi, and R. C. Boucher Mucin Granule Intraluminal Organization in Living Mucous/Goblet Cells: ROLES OF PROTEIN POST-TRANSLATIONAL MODIFICATIONS AND SECRETION J. Biol. Chem., February 24, 2006; 281(8): 4844 - 4855. [Abstract] [Full Text] [PDF]
|
|