Authors: Rena Moromizato, Kodai Fukuda, Shigekatsu Suzuki, Taizo Motomura, Chikako Nagasato, and Yoshihisa Hirakawa Journal: PNAS Pyrenoids are microcompartments that are universally found in the photosynthetic plastids of various eukaryotic algae. They contain ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and play a pivotal role in facilitating CO2 assimilation via CO2-concentrating mechanisms (CCMs). Recent investigations involving model algae have revealed that pyrenoid-associated proteins participate in pyrenoid biogenesis and CCMs. However, these organisms represent only a small part of algal lineages, which limits our comprehensive understanding of the diversity and evolution of pyrenoid-based CCMs. Here we report a pyrenoid proteome of the chlorarachniophyte alga Amorphochlora amoebiformis, which possesses complex plastids acquired through secondary endosymbiosis with green algae. Proteomic analysis using mass spectrometry resulted in the identification of 154 potential pyrenoid components. Subsequent localization experiments demonstrated the specific targeting of eight proteins to pyrenoids. These included a putative Rubisco-binding linker, carbonic anhydrase, membrane transporter, and uncharacterized GTPase proteins. Notably, most of these proteins were unique to this algal lineage. We suggest a plausible scenario in which pyrenoids in chlorarachniophytes have evolved independently, as their components are not inherited from green algal pyrenoids. |
蛋白核是普遍存在于各种真核藻类光合质体中的微室。它们含有核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco），并通过二氧化碳浓缩机制（CO2-concentrating mechanisms, CCMs）在促进二氧化碳同化方面发挥关键作用。近期藻类模式的研究表明，蛋白核相关的蛋白参与了蛋白核生物发生和二氧化碳浓缩机制。然而，这些生物仅代表藻类谱系的一小部分，这限制了我们对以蛋白核为基础的CCMs的多样性和进化的全面理解。本文报道了一种具有复杂质体的绿蜘藻类Amorphochlora amoebiformis，它通过与绿藻的次级内共生获得了蛋白核蛋白组。通过质谱法进行蛋白质组分析，鉴定出154种潜在的蛋白核成分。随后的定位试验验证了八种蛋白对蛋白核的特异性靶向，其中包括推定的Rubisco结合连接蛋白、碳酸酐酶、膜转运蛋白和未表征的GTPase蛋白。值得注意的是，大多数此类蛋白质是这种藻类谱系所特有的。本文提出了一种可能情景，即绿蜘藻类的蛋白核是独立进化的，因为它们的成分不是遗传自绿藻的蛋白核。 （实习生张郑颖编译） |
