Exploring CO2 permeability of plant aquaporins

Abstract

Previous work showed that tobacco aquaporin can mediate CO2 transport and has significant function in photosynthesis and in stomatal opening. However, the CO2 permeability of aquaporins in Arabidopsis had not been fully investigated. Here we study the CO2 permeability of aquaporins expressed in Arabidopsis. We monitored cell swelling under hypotonic conditions to compute osmotic water permeability (Pf), and used microelectrodes to monitor the maximum rise in extracellular surface pH (ΔpHS) caused by CO2 influx into Xenopus oocytes (an index of CO2 permeability). When exposed to CO2, oocytes injected with different subclasses of plant aquaporins had different ΔpHS changes compared with day‐matched H2O‐injected oocytes. Under hypotonic conditions, oocytes injected with different subclasses of plant aquaporins also exhibit different water permeability. In addition, when the plant aquaporins are co‐expressed with other candidate regulators of CO2 transport, we also observed different modulation of ΔpHS. In conclusion, these data implicate a plant aquaporin in Arabidopsis, in the transport not only of water but also of CO2, and raise the possibility of the regulation of CO2 permeability. Funded by AHA 11POST7670014 & ONR N00014‐ 08‐10532.