Aquaporins, found in virtually all living organisms, are membrane-intrinsic proteins that form water-permeable complexes. The mammalian aquaporin AQP1 has also shown CO2 permeability when expressed heterologously in Xenopus oocytes1, although whether this is a biochemical curiosity or of physiological significance is a matter of debate2,3. Here we report that, in the same expression system, a CO2 permeability comparable to that of the human AQP1 is observed for the tobacco plasma membrane aquaporin NtAQP1. NtAQP1 facilitates CO2 membrane transport in the homologous plant system at the cellular level, and has a significant function in photosynthesis and in stomatal opening. NtAQP1 overexpression heightens membrane permeability for CO2 and water, and increases leaf growth. The results indicate that NtAQP1-related CO2 permeability is of physiological importance under conditions where the CO2 gradient across a membrane is small, as is the case between the atmosphere and the inside of a plant cell.
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We thank W. M. Kaiser, M. Eckert and A. Schubert for discussion and help in experimental design.
The authors declare that they have no competing financial interests.
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Uehlein, N., Lovisolo, C., Siefritz, F. et al. The tobacco aquaporin NtAQP1 is a membrane CO2 pore with physiological functions. Nature 425, 734–737 (2003). https://doi.org/10.1038/nature02027
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