Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
J Exp Biol. 2010 Nov 1;213(Pt 21):3644-55. doi: 10.1242/jeb.040881.
Reef-building corals inhabit high light environments and are dependent on photosynthetic endosymbiotic dinoflagellates for nutrition. While photoacclimation responses of the dinoflagellates to changes in illumination are well understood, host photoacclimation strategies are poorly known. This study investigated fluorescent protein expression in the shallow-water coral Acropora yongei during a 30 day laboratory photoacclimation experiment in the context of its dinoflagellate symbionts. Green fluorescent protein (GFP) concentration measured by Western blotting changed reversibly with light intensity. The first 15 days of the photoacclimation experiment led to a ∼1.6 times increase in GFP concentration for high light corals (900 μmol quanta m⁻² s⁻¹) and a ∼4 times decrease in GFP concentration for low light corals (30 μmol quanta m⁻² s⁻¹) compared with medium light corals (300 μmol quanta m⁻² s⁻¹). Green fluorescence increased ∼1.9 times in high light corals and decreased ∼1.9 times in low light corals compared with medium light corals. GFP concentration and green fluorescence intensity were significantly correlated. Typical photoacclimation responses in the dinoflagellates were observed including changes in density, photosynthetic pigment concentration and photosynthetic efficiency. Although fluorescent proteins are ubiquitous and abundant in scleractinian corals, their functions remain ambiguous. These results suggest that scleractinian corals regulate GFP to modulate the internal light environment and support the hypothesis that GFP has a photoprotective function. The success of photoprotection and photoacclimation strategies, in addition to stress responses, will be critical to the fate of scleractinian corals exposed to climate change and other stressors.
造礁珊瑚栖息在高光环境中，依赖共生的光合甲藻获取营养。尽管甲藻对光照变化的光适应反应已得到充分研究，但宿主的光适应策略却知之甚少。本研究在实验室光驯化实验中，调查了浅水珊瑚 Acropora yongei 及其共生甲藻中的荧光蛋白表达。通过 Western blot 测定的绿色荧光蛋白（GFP）浓度随光照强度可逆变化。在光驯化实验的前 15 天，与中光珊瑚（300 μmol 量子 m ⁻² s ⁻¹ ）相比，高光珊瑚（900 μmol 量子 m ⁻² s ⁻¹ ）的 GFP 浓度增加了约 1.6 倍，而低光珊瑚（30 μmol 量子 m ⁻² s ⁻¹ ）的 GFP 浓度则降低了约 4 倍。与中光珊瑚相比，高光珊瑚的绿色荧光增加了约 1.9 倍，而低光珊瑚则降低了约 1.9 倍。GFP 浓度与绿色荧光强度显著相关。观察到典型的甲藻光适应反应，包括密度、光合色素浓度和光合效率的变化。尽管荧光蛋白在石珊瑚中普遍存在且丰富，但它们的功能仍不清楚。这些结果表明，石珊瑚通过调节 GFP 来调节内部光环境，并支持 GFP 具有光保护功能的假说。除了应激反应外，光保护和光适应策略的成功对于暴露于气候变化和其他胁迫源的石珊瑚的命运将至关重要。
