Barott Katie L, Venn Alexander A, Perez Sidney O, Tambutté Sylvie, Tresguerres Martin
Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093;
Marine Biology Department, Centre Scientifique de Monaco, MC-98000 Monaco, Monaco; and Laboratoire Européen Associé 647 "Biosensib," Centre Scientifique de Monaco-Centre National de la Recherche Scientifique, MC-98000 Monaco, Monaco.
Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):607-12. doi: 10.1073/pnas.1413483112. Epub 2014 Dec 29.
Symbiotic dinoflagellate algae residing inside coral tissues supply the host with the majority of their energy requirements through the translocation of photosynthetically fixed carbon. The algae, in turn, rely on the host for the supply of inorganic carbon. Carbon must be concentrated as CO2 in order for photosynthesis to proceed, and here we show that the coral host plays an active role in this process. The host-derived symbiosome membrane surrounding the algae abundantly expresses vacuolar H(+)-ATPase (VHA), which acidifies the symbiosome space down to pH ∼ 4. Inhibition of VHA results in a significant decrease in average H(+) activity in the symbiosome of up to 75% and a significant reduction in O2 production rate, a measure of photosynthetic activity. These results suggest that host VHA is part of a previously unidentified carbon concentrating mechanism for algal photosynthesis and provide mechanistic evidence that coral host cells can actively modulate the physiology of their symbionts.
生活在珊瑚组织内的共生甲藻通过光合固定碳的转运为宿主提供大部分能量需求。反过来，这些藻类则依赖宿主提供无机碳。为了使光合作用得以进行，碳必须以二氧化碳的形式被浓缩，在此我们表明珊瑚宿主在这一过程中发挥着积极作用。围绕藻类的源自宿主的共生体膜大量表达液泡H(+) -ATP酶（VHA），该酶将共生体空间酸化至pH约为4。抑制VHA会导致共生体中平均H(+)活性显著降低，降幅高达75%，同时光合活性指标氧气产生速率也显著降低。这些结果表明宿主VHA是藻类光合作用中一个此前未被识别的碳浓缩机制的一部分，并提供了珊瑚宿主细胞可主动调节其共生体生理机能的机制证据。
