In response to fluctuation in light intensity and quality, oxygenic photosynthetic organisms modify their light-harvesting and excitation energy-transfer processes to maintain optimal photosynthetic activity. Glaucophytes, which are a group of primary symbiotic algae, possess light-harvesting antennas called phycobilisomes (PBSs) consistent with cyanobacteria and red algae. However, compared with cyanobacteria and red algae, glaucophytes are poorly studied and there are few reports on the regulation of photosynthesis in the group. In this study, we examined the long-term light adaptation of light-harvesting functions in a glaucophyte, Cyanophora paradoxa, grown under different light conditions. Compared with cells grown under white light, the relative number of PBSs to photosystems (PSs) increased in blue-light-grown cells and decreased in green-, yellow-, and red-light-grown cells. Moreover, the PBS number increased with increment in the monochromatic light intensity. More energy was transferred from PBSs to PSII than to PSI under blue light, whereas energy transfer from PBSs to PSII was reduced under green and yellow lights, and energy transfer from the PBSs to both PSs decreased under red light. Decoupling of PBSs was induced by intense green, yellow, and red lights. Energy transfer from PSII to PSI (spillover) was observed, but the contribution of the spillover did not distinctly change depending on the culture light intensity and quality. These results suggest that the glaucophyte C. paradoxa modifies the light-harvesting abilities of both PSs and excitation energy-transfer processes between the light-harvesting antennas and both PSs during long-term light adaption.

为了响应光强度和质量的波动，含氧光合生物会改变其光捕获和激发能量转移过程，以维持最佳的光合活性。灰藻是一组初级共生藻类，拥有与蓝藻和红藻一致的称为藻胆体（PBS）的光捕获天线。然而，与蓝藻和红藻相比，蓝藻的研究较少，对其光合作用调控的报道也很少。在这项研究中，我们研究了在不同光照条件下生长的蓝藻（ Cyanophora paradoxa ）的光捕获功能的长期光适应。与白光下生长的细胞相比，蓝光生长的细胞中 PBS 与光系统 (PS) 的相对数量增加，绿光、黄光和红光生长的细胞中 PBS 相对数量减少。此外，PBS 数量随着单色光强度的增加而增加。在蓝光下，从 PBS 转移到 PSII 的能量多于转移到 PSI 的能量，而在绿光和黄光下，从 PBS 到 PSII 的能量转移减少，在红光下，从 PBS 到两个 PS 的能量转移减少。强绿光、黄光和红光诱导 PBS 解偶联。观察到从 PSII 到 PSI 的能量转移（溢出），但溢出的贡献并没有根据培养光强度和质量发生明显变化。这些结果表明，在长期的光适应过程中，灰绿植物C. paradoxa改变了两个 PS 的光捕获能力以及光捕获天线和两个 PS 之间的激发能量转移过程。