Proton-pumping rhodopsins (PPRs) utilize sunlight to produce cellular energy. They are widely distributed in marine phytoplankton and were recently shown to occur in the vacuolar membrane of a marine diatom, making the vacuole a second light transducing organelle. Of course, the first, the chloroplast, is where photosynthesis occurs. However, the two light-driven sources of cellular energy are quite different and, in many ways, complement one another. Photosynthesis works best at low to intermediate light intensities, and is inhibited at high light, while PPR is predicted to work best at high light intensities. And photosynthetic rates decrease with decreasing temperature and are subject to iron limitation, while PPR photochemistry is not directly limited by iron, and is unaffected by temperature. Thus, the two phototrophic systems are favored under different sets of conditions. Placing PPR in the vacuole may benefit this complementary situation where one or the other phototrophic process is favored depending on the environmental conditions. And here, the presence of PPR in the vacuole may be especially beneficial for growth and survival as that organelle often acts as a storage site for cellular energy in the form of the phosphate anhydride bonds of polyphosphates. We hypothesize that this complementary behavior, along with the ability to store excess energy produced by PPR in the vacuole as high energy polyphosphates, represents an important survival strategy in the ocean, where light, iron levels, and temperature vary widely on a variety of spatial and temporal scales.

中文翻译：

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质子泵视紫红质促进高度变化海洋中浮游植物的生长和生存


质子泵视紫红质 (PPR) 利用阳光产生细胞能量。它们广泛分布在海洋浮游植物中，最近被证明存在于海洋硅藻的液泡膜中，使液泡成为第二个光传导细胞器。当然，第一个是叶绿体，是光合作用发生的地方。然而，这两种光驱动的细胞能量来源截然不同，并且在许多方面相互补充。光合作用在低至中等光强度下效果最佳，在高光强度下受到抑制，而 PPR 预计在高光强度下效果最佳。光合速率随温度降低而降低，并受到铁的限制，而PPR光化学不直接受铁的限制，并且不受温度的影响。因此，这两种光养系统在不同的条件下受到青睐。将 PPR 置于液泡中可能有利于这种互补情况，其中根据环境条件有利于一种或另一种光养过程。在这里，液泡中 PPR 的存在可能对生长和存活特别有益，因为该细胞器通常以多磷酸盐的磷酸酐键的形式充当细胞能量的储存位点。我们假设这种互补行为，以及将 PPR 产生的多余能量存储在液泡中作为高能聚磷酸盐的能力，代表了海洋中的一种重要的生存策略，因为在海洋中，光、铁水平和温度在各种空间上变化很大。和时间尺度。