Regulation of green fluorescent proteins by Sea Anemones (Anthopleura spp.) in response to light

Green Fluorescent Proteins (GFPs) are a family of proteins with a disjunct systematic distribution; their biological functions remain speculative for the most part. Here we report studies of 3 closely related species of green sea anemones (Anthopleura) that express GFPs throughout their ectoderm. Individuals of these species maintain facultative symbiosis with zooxanthellae in their endoderm and inhabit the rocky intertidal or shallow subtidal. Thus, they depend on exposure to light to maintain photosynthesis of their symbionts, and simultaneously need to manage stresses associated with this exposure. We present experimental evidence that these sea anemones regulate the amount of GFP in their bodies in response to the surrounding light environment: they increase or reduce GFP when exposed to brighter or dimmer light, respectively, yet they maintain some GFP while in darkness, for surprisingly long periods.

Methods
In general, we exposed sea anemones from the genus Anthopleura to variable-intensity light environments, then quantified either GFP directly or green fluorescence intensity as a stand-in for GFP. Methods and analysis were variable, please see article for further details.

绿色荧光蛋白（Green Fluorescent Proteins，GFPs）是一类系统分布呈间断格局的蛋白家族，其生物学功能在很大程度上仍处于推测阶段。本研究针对3种亲缘关系密切的绿色海葵（海葵属Anthopleura）展开，这类海葵的外胚层全程表达绿色荧光蛋白。该类物种的个体与其内胚层中的虫黄藻（zooxanthellae）建立兼性共生关系，且栖息于岩质潮间带或浅潮下带生境中。因此，它们依赖光照以维持共生体的光合作用，同时也需应对光照暴露所引发的各类胁迫。本研究提供实验证据表明，这类海葵会根据周围光照环境调节体内绿色荧光蛋白的含量：当处于强光环境时上调GFP表达，弱光环境下则下调其表达；即便处于完全黑暗的环境中，它们仍能维持一定水平的GFP表达，且持续时长远超预期。

方法
总体而言，本研究将海葵属（Anthopleura）的海葵暴露于不同光照强度的环境中，随后或直接定量检测GFP含量，或以绿色荧光强度作为GFP的替代指标进行量化分析。由于实验方法与分析流程存在差异，详细内容请参阅原文。