Overexpression of Rboh enhances inorganic carbon acquisition through coordinating with carbonic anhydrase in Pyropia yezoensis

Pyropia yezoensis is an important intertidal economic macroalgae, which is periodically affected by various stresses, such as the limitation of inorganic carbon (C_i) deficiency. Under such environment, the redox homeostasis within the cells of P. yezoensis is seriously affected, and the reactive oxygen species (ROS) signal transduction system would be activated to regulate the photosynthetic activity. Therefore, how P. yezoensis manage ROS to maintain effective photosynthetic carbon fixation has aroused great interest. Here, we characterize transformants overexpressing respiratory burst oxidase homolog (Rboh), an important gene that can actively produce ROS, at the levels of cellular physiology, biochemistry, and transcriptomics. Our data indicated the expression of Rboh significantly increased, accompanied by a significant upregulated expression of alpha-type carbonic anhydrase 3 (αCA3) and increased extracellular carbonic anhydrase activity in the Rboh overexpressing strains. Interestingly, compared with the wild type, the photosynthetic activity of transgenic strains was significantly higher under the low C_i and high light condition, implying that the ROS signal triggered by overexpression of Rboh was involved in regulating the C_i absorption and utilization in P. yezoensis when the C_i source was limited. In summary, this study provided evidence supporting the correlation between the ROS production and the Ci utilization under stress environments in P. yezoensis.