Diatoms are a diverse group of photosynthetic unicellular algae with a plastid of red-algal origin. As prolific primary producers in the ocean, diatoms fix as much carbon as all rainforests combined. The molecular mechanisms that contribute to the high photosynthetic productivity and ecological success of diatoms are however not yet fully understood. Using the model diatom Phaeodactylum tricornutum, here we show rhythmic transcript accumulation of plastid psaA, psbA, petB, and atpB genes as driven by a free running circadian clock. Treatment with the electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea overrides the circadian signal by markedly downregulating transcription of psaA, petB, and atpB genes but not the psbA gene. Changes in light quantity produce little change in plastid gene transcription while the effect of light quality seems modest with only the psaA gene responding in a pattern that is dependent on the redox state of the plastoquinone pool. The significance of these plastid transcriptional responses and the identity of the underlying genetic control systems are discussed with relevance to diatom photosynthetic acclimation.

硅藻是一组多样化的光合单细胞藻类，具有红藻来源的质体。作为海洋中多产的初级生产者，硅藻固定的碳量相当于所有热带雨林的总和。然而，导致硅藻高光合生产力和生态成功的分子机制尚未完全了解。使用模型硅藻Phaeodactylum tricornutum，我们在这里展示了由自由运行的生物钟驱动的质体psaA、psbA、petB和atpB基因的有节奏的转录积累。用电子传递抑制剂 3-(3,4-二氯苯基)-1,1-二甲基脲处理通过显着下调psaA、petB和atpB基因，但不是psbA基因。光量的变化对质体基因转录几乎没有影响，而光质量的影响似乎不大，只有psaA基因以依赖于质体醌库的氧化还原状态的模式响应。讨论了与硅藻光合驯化相关的这些质体转录反应的重要性和潜在遗传控制系统的身份。