Coelastrella astaxanthina Ki-4, a eukaryotic microalga belonging to the family Scenedesmaceae, survives for long periods under severe photo-oxidative stress conditions associated with the accumulation of water-soluble astaxanthin-binding glycoprotein, named AstaP. It is a novel carotenoprotein in photosynthetic organisms and is involved in photo-oxidative stress protection, but its expression profile during cell survival and relationship with the biosynthesis of the cofactor astaxanthin are almost unknown. In this study, based on the analysis of photosynthesis during cell survival under photo-oxidative stress conditions, we classified the recovery periods of photosynthesis into the following three stages: recovery, tolerance, and cyst stages. Although C. astaxanthina Ki-4 promptly decreased the activity of photosynthesis after the start of photo-oxidative stress treatment, the activity recovered in the early recovery stage, where the expression of the transcript encoding AstaP was significantly upregulated. In the tolerant stage, red-coloration and enlargement of cells were gradually increased, and the accumulation of the AstaP protein was also significantly increased. C. astaxanthina Ki-4 cells presented a large amount of lutein before the stress treatment, which was decreased with the gradual increase in secondary carotenoids, such as canthaxanthin, adonixanthin, and astaxanthin. Although astaxanthin was quantified to be almost equal to that of the other secondary carotenoids, astaxanthin was detected as the main carotenoid binding to AstaP. These results suggest that AstaP preferentially binds to astaxanthin in vivo and contributes to photo-oxidative stress protection mainly in the tolerance stage.

Coelastrella astaxanthina Ki-4，一种属于景物科的真核微藻，在与称为AstaP的水溶性虾青素结合糖蛋白的积累相关的严重光氧化应激条件下可以长期存活。它是光合生物中的一种新型胡萝卜素蛋白，参与光氧化应激保护，但在细胞存活期间其表达谱以及与辅因子虾青素生物合成的关系几乎是未知的。在这项研究中，基于在光氧化应激条件下细胞存活期间光合作用的分析，我们将光合作用的恢复期分为以下三个阶段：恢复，耐受和囊肿阶段。虽然虾青虫开始光氧化应激处理后，Ki-4迅速降低了光合作用的活性，该活性在早期恢复阶段恢复，其中编码AstaP的转录物的表达明显上调。在耐受阶段，细胞的红色和肿胀逐渐增加，AstaP蛋白的积累也显着增加。虾青素Ki-4细胞在应激处理前呈现大量的叶黄素，随着叶黄素，Adonixanthin和虾青素等次要类胡萝卜素的逐渐增加而降低。尽管虾青素被定量为几乎与其他次要类胡萝卜素相等，但虾青素被检测为与AstaP结合的主要类胡萝卜素。这些结果表明，AstaP在体内优先结合虾青素，并且主要在耐受阶段有助于光氧化应激保护。