Inorganic carbon uptake for photosynthesis by the symbiotic coral-dinoflagellate association .2. Mechanisms for bicarbonate uptake
Inorganic carbon uptake for photosynthesis by the symbiotic coral-dinoflagellate association .2. Mechanisms for bicarbonate uptake
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DOI：
10.1016/0022-0981(95)00202-2
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发表时间：
1996-08-01
影响因子：
2
通讯作者：
Jaubert, J
中科院分区：
文献类型：
--
作者：
AlMoghrabi, S;Goiran, C;Jaubert, J
胞内共生菌作为光合作用中溶解无机碳(DIC)来源的HCO3吸收机制。利用簇状珊瑚、新鲜分离的虫黄藻(FIZ)和培养的虫黄藻(CZ)的微菌落进行了研究。为此，我们使用了阴离子转运的特异性抑制剂4-acetamido-4‘-isothiocyanatostilbene-2，2’-disulfonic酸-SITS-，4，4‘-diisothiocyanato-stilbene-2，2’-disulfonic酸-DIDS-，碳酸酐酶(乙酰唑胺，乙氧基唑胺)，H+-ATPase(N，N‘-二环己基碳二亚胺-DCCD-，己烯雌酚-DES-，钒酸)或钙通道(维拉帕米)。我们还测试了已知在HCO3转运中起作用的离子，如Na+和Ca2+的影响。还进行了氯离子吸收实验，以确定CZ中是否耦合了Cl-和HCO3-助熔剂。我们的结果表明，动物共生体对碳酸氢盐的摄取很可能是通过两种类型的DDS敏感的HCO；载体实现的，每种载体共享总摄取量的50%。第一种是Na+依赖的，第二种是非Na+依赖的。我们认为存在Na+非依赖的Cl-/HCO3-交换和依赖于Na+的Cl-HCO3-交换或Na+/HCO3-共存。药理数据表明，碳酸氢酶在维持光合作用速率方面起着重要作用。在完整的共生体中，碳酸氢酶活性的主要部分位于虫黄藻。FIZ和CZ的DIC吸收机理存在显著差异。在FIZ，H+-ATPase和碳酸酐酶参与碳素供应，而在CZ，HCO3-吸收机制似乎严格依赖于Na+，可能是Na+/HCO3-共运体活性的结果。我们假设，动物宿主对HCO3吸收的刺激是由虫黄藻光合作用引起的细胞内pH碱化的结果。这些结果在宿主细胞和分离的虫黄藻吸收DIC的合成方案中进行了总结。
Mechanisms of HCO3- uptake as a source of dissolved inorganic carbon (DIC) for photosynthesis by the intracellular symbiont, Symbiodinium sp. were studied using microcolonies of the coral Galaxea fascicularis, freshly isolated zooxanthellae (FIZ) and cultured zooxanthellae (CZ). For this purpose we used specific inhibitors of anion transport 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid - SITS -, 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid - DIDS -, carbonic anhydrase (acetazolamide, ethoxyzolamide), H+-ATPase (N,N'-dicyclohexylcarbodiimide - DCCD -, diethylstilbestrol - DES -, vanadate) or Ca2+ channels (verapamil). We also tested the effect of ions known to play a role in HCO3- transport, like Na+ and Ca2+. Chloride uptake experiments were also performed to determine whether Cl- and HCO3- fluxes were coupled in CZ. Furthermore, the presence of carbonic anhydrase was tested using indirect immunoflurescence.Our results suggest that bicarbonate uptake by the animal symbiont is likely to be achieved by two types of DIDS-sensitive HCO; carriers, each sharing 50% of the total uptake. The first is Na+-dependent, while the second is Na+-independent. We suggest the presence of a Na+-independent Cl-/HCO3- exchange and either a Na+-dependent Cl-HCO3- exchange or a Na+/HCO3- symport. Pharmacological data suggest that the enzyme carbonic anhydrase plays an important role in maintaining the photosynthetic rate. In the intact symbiosis, the major fraction of carbonic anhydrase activity is located in the zooxanthellae. Striking differences in DIC absorption mechanisms were found for FIZ and CZ. In FIZ, H+-ATPase and carbonic anhydrase participate in the carbon supply while in CZ the mechanism of HCO3- uptake appears to be strictly Na+-dependent and could be the result of Na+/HCO3- symport activity. We hypothesize that stimulation of HCO3- uptake by the animal host is a consequence of intracellular pH alkalization by zooxanthellae photosynthesis. These results were summarized in a synthetic scheme of DIC absorption by both host cell and isolated zooxanthellae.