Integrated RNA-seq and Proteomic Studies Reveal Resource Reallocation towards Energy Metabolism and Defense in in Response to CO Increase.

Rising atmospheric CO concentrations are causing ocean acidification (OA) with significant consequences for marine organisms. Because CO is essential for photosynthesis, the effect of elevated CO on phytoplankton is more complex and the mechanism is poorly understood. Here we applied RNA-seq and iTRAQ proteomics to investigate the impacts of CO increase (from ∼400 to 1000 ppm) on the temperate coastal marine diatom We identified 32,389 differentially expressed genes (DEGs) and 1,826 differentially expressed proteins (DEPs) from elevated CO conditions, accounting for 48.5% of total genes and 25.9% of total proteins we detected, respectively. Elevated CO significantly inhibited the growth of , and the 'omic' data suggested that this might be due to compromised photosynthesis in the chloroplast and raised mitochondrial energy metabolism. Furthermore, many genes/proteins associated with nitrogen metabolism, transcriptional regulation, and translational regulation were markedly up-regulated, suggesting enhanced protein synthesis. In addition, exhibited higher capacity of ROS production and resistance to oxidative stress. Overall, elevated CO seems to repress photosynthesis and growth of , and through massive gene expression reconfiguration induce cells to increase investment in protein synthesis, energy metabolism and antioxidative stress defense, likely to maintain pH homeostasis and population survival. This survival strategy may deprive this usually dominant diatom in temperate coastal waters of its competitive advantages in acidified environments. Rising atmospheric CO concentrations are causing ocean acidification with significant consequences for marine organisms. Chain-forming centric diatoms of Skeletonema is one of the most successful groups of eukaryotic primary producers with widespread geographic distribution. Among the recognized 28 species, can be a useful model for investigating the ecological, genetic, physiological, and biochemical characteristics of diatoms in temperate coastal regions. In this study, we found that the elevated CO seems to repress photosynthesis and growth of , and through massive gene expression reconfiguration induce cells to increase investment in protein synthesis, energy metabolism and antioxidative stress defense, likely to maintain pH homeostasis and population survival. This survival strategy may deprive this usually dominant diatom in temperate coastal waters of its competitive advantages in acidified environments.