Poster: Membrane Transport

Abs # 1202: CO₂ uptake, photosynthesis and plant-growth is affected by the function of the plasmamembrane aquaporin NtAQP1 as a CO₂-transporter in tobacco

Presenter:	Kaldenhoff, Ralf , kaldenhoff@botanik.uni-wuerzburg.de
Authors	Kaldenhoff, Ralf  (A)   Uehlein, Norbert  (A)   Siefritz, Franka  (A)   Otto, Beate  (A)   Lovisolo, Claudio  (B)
Affiliations:	(A): Julius-von-Sachs-Institut f. Biowissenschaften, University of Wuerzburg (B): Dipartimento Colture arboree, Università di Torino
Web Site:	http://www.botanik.uni-wuerzburg.de/bot1/akkalden/main.html

Aquaporins are water transporting membrane intrinsic proteins expressed in virtually all living organisms. Common to these proteins is their water permeability which is in some instances highly selective, in others also includes small polar molecules. Hitherto, permeability for CO₂ was just found for the mammalian AQP1 heterologously expressed in Xenopus oocytes. It is a matter of an ongoing discussion, whether this function is significant for physiology, because AQP1 knock out mice do not show differences in CO₂ exchange. Expression of the plant aquaporin NtAQP1 in the same heterologous expression system resulted in a CO₂ permeability, which is comparable to that of AQP1. Physiological studies in plants with a reduced NtAQP1 expression or an induced overexpression of this protein do show significant different cellular CO₂ permeability. Physiological consequences were an aberrant behaviour in stomatal opening due to a change in a CO₂ dependent negative feedbacksystem and a net photosynthesis that was influenced by the NtAQP1 expression level. As a result of NtAQP1 overexpression plants show a drastically increased leaf growth rate. NtAQP1 is an example of a CO₂ permeable aquaporin, which indicates that this function could be of major significance in physiological processes.