Different Regulatory Modes of Synechocystis sp. PCC 6803 in Response to Photosynthesis Inhibitory Conditions

Cyanobacteria are promising industrial platforms owing to their ability to produce diverse natural secondary metabolites and nonnative value-added biochemicals from CO2 and light. To fully utilize their industrial potency, it is critical to understand their photosynthetic efficiency under various environmental conditions. In this study, we elucidated the inhibitory mechanisms of photosynthesis under highlight and low-temperature stress conditions in the model cyanobacterium Synechocystis sp. PCC 6803. Under each stress condition, the transcript abundance and translation efficiency were measured using transcriptome sequencing (RNA-seq) and ribosome profiling, and the genome-wide transcription unit architecture was constructed by data integration of transcription start sites and transcript 3'-end positions obtained from differential RNA-seq and sequencing of 3'-ends (Term-seq), respectively. Our results suggested that the mode of photosynthesis inhibition differed between the two stress conditions; high light stress induced photodamage responses, while low temperature stress impaired the translation efficiency of photosynthesis-associated genes. In particular, poor translation of photosystem I resulted from ribosome stalling at the untranslated regions, affecting the overall photosynthetic yield under low temperature stress. Our comprehensive multiomics analysis with transcription unit architecture provides foundational information on photosynthesis for future industrial strain development. IMPORTANCE Cyanobacteria are a compelling biochemical production platform for their ability to propagate using light and atmospheric CO2 via photosynthesis. However, the engineering of strains is hampered by limited understanding of photosynthesis under diverse environmental conditions such as high-light and low-temperature stresses. Herein, we decipher the transcriptomic and translatomic responses of the photosynthetic efficiency to stress conditions using the integrative analysis of multiomic data generated by RNA-seq and ribosome profiling, respectively. Through the generated massive data, along with the guide of the genome-wide transcription unit architecture constructed by transcription start sites and transcript 3'-end positions, we identified the factors affecting photosynthesis at transcription, posttranscription, and translation levels. Importantly, the high-light stress induces photodamage responses, and the low-temperature stress cripples the translation efficiency of photosynthesis-associated genes. The resulting insights provide pivotal information for future cyanobacterial cell factories powered by the engineering toward robust photosynthesis ability.