Coesel Sacha N, Durham Bryndan P, Groussman Ryan D, Hu Sarah K, Caron David A, Morales Rhonda L, Ribalet François, Armbrust E Virginia
School of Oceanography, University of Washington, Seattle, WA 98195;
Department of Biology, Genetics Institute, University of Florida, Gainesville, FL 32610.
Proc Natl Acad Sci U S A. 2021 Feb 9;118(6). doi: 10.1073/pnas.2011038118.
The 24-h cycle of light and darkness governs daily rhythms of complex behaviors across all domains of life. Intracellular photoreceptors sense specific wavelengths of light that can reset the internal circadian clock and/or elicit distinct phenotypic responses. In the surface ocean, microbial communities additionally modulate nonrhythmic changes in light quality and quantity as they are mixed to different depths. Here, we show that eukaryotic plankton in the North Pacific Subtropical Gyre transcribe genes encoding light-sensitive proteins that may serve as light-activated transcription factors, elicit light-driven electrical/chemical cascades, or initiate secondary messenger-signaling cascades. Overall, the protistan community relies on blue light-sensitive photoreceptors of the cryptochrome/photolyase family, and proteins containing the Light-Oxygen-Voltage (LOV) domain. The greatest diversification occurred within Haptophyta and photosynthetic stramenopiles where the LOV domain was combined with different DNA-binding domains and secondary signal-transduction motifs. Flagellated protists utilize green-light sensory rhodopsins and blue-light helmchromes, potentially underlying phototactic/photophobic and other behaviors toward specific wavelengths of light. Photoreceptors such as phytochromes appear to play minor roles in the North Pacific Subtropical Gyre. Transcript abundance of environmental light-sensitive protein-encoding genes that display diel patterns are found to primarily peak at dawn. The exceptions are the LOV-domain transcription factors with peaks in transcript abundances at different times and putative phototaxis photoreceptors transcribed throughout the day. Together, these data illustrate the diversity of light-sensitive proteins that may allow disparate groups of protists to respond to light and potentially synchronize patterns of growth, division, and mortality within the dynamic ocean environment.
昼夜24小时的光暗循环控制着生命各个领域复杂行为的日常节律。细胞内的光感受器能感知特定波长的光，这些光可以重置内部生物钟和/或引发不同的表型反应。在海洋表层，微生物群落随着被混合到不同深度，还会调节光质和光量的非节律性变化。在此，我们表明，北太平洋亚热带环流中的真核浮游生物转录编码光敏感蛋白的基因，这些蛋白可能充当光激活转录因子、引发光驱动的电/化学级联反应或启动第二信使信号级联反应。总体而言，原生生物群落依赖隐花色素/光解酶家族的蓝光敏感光感受器以及含有光-氧-电压（LOV）结构域的蛋白。最大程度的多样化发生在定鞭藻门和光合不等鞭毛藻中，其中LOV结构域与不同的DNA结合结构域和第二信号转导基序相结合。具鞭毛的原生生物利用绿光感应视紫红质和蓝光色素蛋白，这可能是针对特定波长光的趋光性/避光性及其他行为的潜在基础。诸如植物色素之类的光感受器在北太平洋亚热带环流中似乎发挥着次要作用。发现显示出昼夜模式的环境光敏感蛋白编码基因的转录本丰度主要在黎明时达到峰值。例外情况是LOV结构域转录因子，其转录本丰度在不同时间达到峰值，以及假定的趋光性光感受器在全天都有转录。这些数据共同说明了光敏感蛋白的多样性，这些多样性可能使不同种类的原生生物对光做出反应，并有可能在动态海洋环境中使生长、分裂和死亡模式同步。
