Secretion in unicellular marine phytoplankton:: Demonstration of regulated exocytosis in Phaeocystis globosa

被引:65
作者
Chin, WC
Orellana, MV
Quesada, I
Verdugo, P [1 ]
机构
[1] Florida State Univ, FAMU, Dept Chem Engn, Biomed Engn Program, Tallahassee, FL 32310 USA
[2] Inst Syst Biol, Seattle, WA 98103 USA
[3] Univ Washington, Dept Bioengn, Seattle, WA 98195 USA
[4] Univ Washington, Friday Harbor Labs, Seattle, WA 98195 USA
基金
美国国家科学基金会;
关键词
exocytosis; exopolymer; granule; light; mucilage; Phaeocystis;
D O I
10.1093/pcp/pch062
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
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 (lambda = 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.
引用
收藏
页码:535 / 542
页数:8
相关论文
共 56 条
[1]  
AARONSON S, 1971, LIMNOL OCEANOGR, V16, P1
[2]  
Aitken M L, 1989, Symp Soc Exp Biol, V43, P73
[3]   Microbial control of oceanic carbon flux: The plot thickens [J].
Azam, F .
SCIENCE, 1998, 280 (5364) :694-696
[4]   THE PRODUCTION OF DISSOLVED ORGANIC-MATTER BY PHYTOPLANKTON AND ITS IMPORTANCE TO BACTERIA - PATTERNS ACROSS MARINE AND FRESH-WATER SYSTEMS [J].
BAINES, SB ;
PACE, ML .
LIMNOLOGY AND OCEANOGRAPHY, 1991, 36 (06) :1078-1090
[5]   THE CONTROL OF EXOCYTOSIS IN PLANT-CELLS [J].
BATTEY, NH ;
BLACKBOURN, HD .
NEW PHYTOLOGIST, 1993, 125 (02) :307-338
[6]   Localization of Ca2+ extrusion sites in pancreatic acinar cells [J].
Belan, PV ;
Gerasimenko, OV ;
Tepikin, AV ;
Petersen, OH .
JOURNAL OF BIOLOGICAL CHEMISTRY, 1996, 271 (13) :7615-7619
[7]   PHYTOPLANKTON EXUDATION OF ORGANIC-MATTER - WHY DO HEALTHY CELLS DO IT [J].
BJORNSEN, PK .
LIMNOLOGY AND OCEANOGRAPHY, 1988, 33 (01) :151-154
[8]   Spontaneous assembly of marine dissolved organic matter into polymer gels [J].
Chin, WC ;
Orellana, MV ;
Verdugo, P .
NATURE, 1998, 391 (6667) :568-572
[9]   IONIC CONTROL OF THE SIZE OF THE VESICLE MATRIX OF BEIGE MOUSE MAST-CELLS [J].
CURRAN, MJ ;
BRODWICK, MS .
JOURNAL OF GENERAL PHYSIOLOGY, 1991, 98 (04) :771-790
[10]  
DAVIES D, 1995, J CRYPTOL, V8, P1, DOI 10.1007/BF00204799