Chlorella pyrenoidosa is a microalga that holds enormous potential as a source of renewable energy. Nuclear radiation is commonly used to modify natural microalgal phenotypes to enhance specified functions. However, the mechanisms underlying such modifications are poorly understood. Here, we use a multidisciplinary approach to analyze wild-type Chlorella pyrenoidosa and a nuclear-irradiated mutant known for its higher growth rate and photosynthetic efficiency. A combination of focused ion beam scanning electron microscopy (FIB-SEM), cryo-FIB milling, and cryo-electron tomography (cryo-ET) achieve visualization of the microalgae and their organelles in unprecedented detail. Compared to the wild-type cell, the nuclear-irradiated mutant and its subcellular organelles, including the chloroplast, significantly increase in volume by 1.2-fold. Moreover, proteomics and metabolomics data indicate rubisco overexpression by 1.07-fold in the mutant, consistent with enhancement of carbon fixation in photosynthesis and the observed enlargement of subcellular morphology. Furthermore, cryo-ET reveals enlarged membrane width in the thylakoid of the mutant, suggesting an upregulation role for chlorophyll synthesis and chloroplast construction. Collectively, our studies reveal the detailed architectures of C. pyrenoidosa wild-type and a mutant with higher growth rate and photosynthetic efficiency, providing a basis for understanding how subcellular organelles function collaboratively to support macroscopic traits.

蛋白核小球藻是一种微藻，具有作为可再生能源的巨大潜力。核辐射通常用于修饰天然微藻表型以增强特定功能。然而，人们对这种修改背后的机制知之甚少。在这里，我们使用多学科方法来分析野生型蛋白核小球藻以及以更高的生长速度和光合作用效率而闻名的核辐射突变体。聚焦离子束扫描电子显微镜 (FIB-SEM)、cryo-FIB 铣削和低温电子断层扫描 (cryo-ET) 的组合以前所未有的细节实现了微藻及其细胞器的可视化。与野生型细胞相比，核辐射突变体及其亚细胞器（包括叶绿体）的体积显着增加了 1.2 倍。此外，蛋白质组学和代谢组学数据表明，突变体中 rubisco 过度表达了 1.07 倍，这与光合作用中碳固定的增强和观察到的亚细胞形态的扩大一致。此外，cryo-ET 揭示了突变体类囊体中膜宽度的扩大，表明叶绿素合成和叶绿体构建的上调作用。总的来说，我们的研究揭示了C. pyrenoidosa野生型和具有更高生长速率和光合效率的突变体，为理解亚细胞细胞器如何协同作用以支持宏观特征提供了基础。