Tobacco aquaporin NtAQP1 and human aquaporin hAQP1 contribute to single cell photosynthesis in Synechococcus

Background Information Aquaporins are H 2 O‐permeable membrane protein pores. However, some aquaporins are also permeable to other substances such as CO 2 . In higher plants, overexpression of such aquaporins has already led to an enhanced photosynthetic performance due to improved CO 2 mesophyll conductance. In this work, we investigated the effects of such aquaporins on unicellular photosynthetically active organisms, specifically cyanobacteria. Results Overexpression of aquaporins NtAQP1 or hAQP1 that might have a function to improve CO 2 membrane permeability lead to increased photosynthesis rates in the cyanobacterium Synechococcus sp . PCC7002 as concluded by the rate of evolved O 2 . A shift in the Plastoquinone pool state of the cells supports our findings. Water permeable aquaporins without CO 2 permeability, such as NtPIP2;1, do not have this effect. Conclusions and Significance We conclude that also in single cell organisms like cyanobacteria, membrane CO 2 conductivity could be rate limiting and CO 2 ‐porins reduce the respective membrane resistance. We could show that besides the tobacco aquaporin NtAQP1 also the human hAQP1 most likely functions as CO 2 diffusion facilitator in the photosynthesis assay.