Cyanobacteria have evolved various photoacclimation processes to perform oxygenic photosynthesis under different light environments. Chromatic acclimation (CA) is a widely recognized and ecologically important type of photoacclimation, whereby cyanobacteria alter the absorbing light colors of a supermolecular antenna complex called the phycobilisome. To date, several CA variants that regulate the green-absorbing phycoerythrin (PE) and/or the red-absorbing phycocyanin (PC) within the hemi-discoidal form of phycobilisome have been characterized. In this study, we identified a unique CA regulatory gene cluster encoding yellow–green-absorbing phycoerythrocyanin (PEC) and a rod-membrane linker protein (CpcL) for the rod-shaped form of phycobilisome. Using the cyanobacterium Leptolyngbya sp. PCC 6406, we revealed novel CA variants regulating PEC (CA7) and the rod-shaped phycobilisome (CA0), which maximize yellow–green light-harvesting capacity and balance the excitation of photosystems, respectively. Analysis of the distribution of CA gene clusters in 445 cyanobacteria genomes revealed eight CA variants responding to green and red light, which are classified based on the presence of PEC, PE, cpcL, and CA photosensor genes. Phylogenetic analysis further suggested that the emergence of CA7 was a single event and preceded that of heterocystous strains, whereas the acquisition of CA0 occurred multiple times. Taken together, these results offer novel insights into the diversity and evolution of the complex cyanobacterial photoacclimation mechanisms.

蓝细菌已经进化出各种光适应过程，以在不同的光照环境下进行氧气的光合作用。色适应（CA）是一种广为人知且具有生态学意义的光适应类型，其中，蓝细菌会改变称为藻胆体的超分子天线复合体的吸收光色。迄今为止，已经表征了调节半胆甾型藻胆体中吸收绿色的藻红蛋白（PE）和/或吸收红色的藻蓝蛋白（PC）的几种CA变体。在这项研究中，我们确定了一个独特的CA调节基因簇，该簇编码吸收黄绿色的藻红蛋白（PEC）和杆状膜连接蛋白（CpcL）的杆状形式的藻胆体。使用蓝细菌的钩端螺旋体sp。PCC 6406，我们揭示了调节PEC（CA7）和棒状藻胆体（CA0）的新型CA变体，它们分别最大化了黄绿色光的收集能力并平衡了光系统的激发。对445个蓝细菌基因组中CA基因簇的分布进行分析后，发现了8个响应绿光和红光的CA变体，这些变体是根据PEC，PE，cpcL和CA光传感器基因的存在进行分类的。系统发育分析进一步表明，CA7的出现是一个单一的事件，并且先于异囊菌株，而CA0的获得却发生了多次。综上所述，这些结果为复杂的蓝细菌光驯化机制的多样性和进化提供了新颖的见解。