Chromatic acclimation in phototrophic marine cryptophytes

色驯化（CA）是一个相当好理解的过程中，在某些蓝藻优化光合光捕获在不断变化的光条件。捕光藻胆体（PBS）的组成随着环境光颜色的变化而重构。在先前定义的蓝藻中的CA类型中，分别在绿色和红色照明下改变其吸收绿色光的藻红蛋白（PE）与吸收红光的藻蓝蛋白（PC）的比率的CA类型是众所周知的。海洋蓝藻中的CA 4，其中光吸收藻胆素发色团在PBP内交换，也得到了很好的研究。最近，在某些隐藻藻类中也观察到了类似的现象。隐藻是一种双鞭毛真核微藻，广泛存在于各种水生环境中。许多物种使用独特的藻胆蛋白进行产氧光合作用，与蓝藻不同，藻胆蛋白不组织在PBS中，但可溶于类囊体腔中。由于存在PC 569，海洋物种Hemiselmis cryptochromatica在569 nm处具有主要吸收峰。当在红光下生长时，该主吸收峰向625 nm移动，而对于在绿色光下生长的细胞，569 nm处的峰占主导地位。在这个建议中，我们的目标是阐明这种CA现象在H。隐染色质将从在不同光质量下生长的细胞中分离PC 569，并使用紫外-可见光谱法、HPLC分析和质谱法的组合分析藻胆素和蛋白质组成。将鉴定的藻胆素与由H.隐色菌基因组这些酶将线性四吡咯胆绿素转化为各种捕光藻胆素发色团。由于PC 569可能拥有一个隐藻特异性acryoyl胆色素，胆色素584，我们将采取初步的步骤来阐明这些胆色素的生物合成途径。为此，将通过生物合成蛋白质的特异性抑制来鉴定含丙烯酰基的中间体。随后，将建立酶测定法，为使用传统方法分离酶创造先决条件。总体而言，该项目将有助于更好地了解海洋隐藻对不断变化的光质的适应。

Chromatic acclimation (CA) is a fairly well understood process in certain cyanobacteria that optimizes photosynthetic light-harvesting under changing light conditions. The composition of light-harvesting phycobilisomes (PBS) is remodeled as the ambient light color changes. Of the previously defined CA types in cyanobacteria, those that change their ratio of green light-absorbing phycoerythrin (PE) to red light-absorbing phycocyanin (PC) under green and red illumination, respectively, are well known. CA4 in marine cyanobacteria, in which the light-absorbing phycobilin chromophores are exchanged within the PBP, is also quite well studied. More recently, a similar phenomenon has also been observed in certain cryptophyte algae. Cryptophytes are biflagellate eukaryotic microalgae found in a variety of aquatic habitats. Many species perform oxygenic photosynthesis using unique phycobiliproteins that, unlike those of cyanobacteria, are not organized in PBS but are soluble in the thylakoid lumen. The marine species Hemiselmis cryptochromatica has a major absorption peak at 569 nm due to the presence of the PC569. When growing under red light, this main absorption peak shifts towards 625 nm, while for cells growing under green light, the peak at 569 nm dominates. In this proposal, we aim to elucidate the underlying mechanism of this CA phenomenon in H. cryptochromatica. PC569 will be isolated from cells grown under different light qualities and analyzed for phycobilin and protein composition using a combination of UV-vis spectrometry, HPLC analysis, and mass spectrometry. The identified phycobilins will be compared to those synthesized by the five ferredoxin-dependent bilin reductases encoded in the H. cryptochromatica genome. These enzymes convert the linear tetrapyrrole biliverdin into various light-harvesting phycobilin chromophores. Since PC569 likely possesses one of the cryptophyte-specific acryoyl bilins, bilin 584, we will take initial steps to elucidate the biosynthetic pathway to these bilins. For this purpose, acryoyl-containing intermediates will be identified by specific inhibition of biosynthetic proteins. Subsequently, an enzyme assay will be established to create the prerequisites for enzyme isolation using traditional methods. Overall, this project will contribute to a better understanding of the adaptation of marine cryptophytes to changing light qualities.