Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway.
Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, N-7491, Norway.
Plant J. 2021 Apr;106(1):113-132. doi: 10.1111/tpj.15149. Epub 2021 Feb 16.
The chloroplast signal recognition particle 54 kDa (CpSRP54) protein is a member of the CpSRP pathway known to target proteins to thylakoid membranes in plants and green algae. Loss of CpSRP54 in the marine diatom Phaeodactylum tricornutum lowers the accumulation of a selection of chloroplast-encoded subunits of photosynthetic complexes, indicating a role in the co-translational part of the CpSRP pathway. In contrast to plants and green algae, absence of CpSRP54 does not have a negative effect on the content of light-harvesting antenna complex proteins and pigments in P. tricornutum, indicating that the diatom CpSRP54 protein has not evolved to function in the post-translational part of the CpSRP pathway. Cpsrp54 KO mutants display altered photophysiological responses, with a stronger induction of photoprotective mechanisms and lower growth rates compared to wild type when exposed to increased light intensities. Nonetheless, their phenotype is relatively mild, thanks to the activation of mechanisms alleviating the loss of CpSRP54, involving upregulation of chaperones. We conclude that plants, green algae, and diatoms have evolved differences in the pathways for co-translational and post-translational insertion of proteins into the thylakoid membranes.
叶绿体信号识别颗粒 54kDa（CpSRP54）蛋白是 CpSRP 途径的成员，已知该途径可将蛋白质靶向到植物和绿藻的类囊体膜中。在海洋硅藻三角褐指藻中，CpSRP54 的缺失降低了光合作用复合物的叶绿体编码亚基的积累，表明其在 CpSRP 途径的共翻译部分起作用。与植物和绿藻不同，缺乏 CpSRP54 对三角褐指藻中光捕获天线复合物蛋白和色素的含量没有负面影响，表明硅藻 CpSRP54 蛋白尚未进化到在 CpSRP 途径的翻译后部分发挥作用。与野生型相比，Cpsrp54 KO 突变体显示出改变的光生理响应，在暴露于更高光强度下，具有更强的光保护机制诱导和更低的生长速率。尽管如此，由于激活了缓解 CpSRP54 缺失的机制，包括伴侣蛋白的上调，它们的表型相对较温和。我们得出结论，植物、绿藻和硅藻在将蛋白质共翻译和翻译后插入类囊体膜的途径中已经进化出差异。
