Function of Nicotiana tabacum Aquaporins as Chloroplast Gas Pores Challenges the Concept of Membrane CO₂ Permeability

Photosynthesis is often limited by the rate of CO₂ diffusion from the atmosphere to the chloroplast. The primary resistances for CO₂ diffusion are thought to be at the stomata and at photosynthesizing cells via a combination resulting from resistances of aqueous solution as well as the plasma membra...

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Bibliographic Details
Published in:The Plant cell 2008-03, Vol.20 (3), p.648-657
Main Authors: Uehlein, Norbert, Otto, Beate, Hanson, David T, Fischer, Matthias, McDowell, Nate, Kaldenhoff, Ralf
Format: Article
Language:English
Subjects:
Antibodies
Aquaporins
Aquaporins - genetics
Aquaporins - metabolism
Aquaporins - physiology
Biological membranes
Carbon dioxide
Carbon Dioxide - metabolism
Cell Membrane Permeability
Cell membranes
Chloroplasts
Chloroplasts - genetics
Chloroplasts - metabolism
Chloroplasts - ultrastructure
Fluorescence
Immunohistochemistry
Leaves
Mesophyll cells
Microscopy, Electron, Transmission
Molecular Sequence Data
Nicotiana - genetics
Nicotiana - metabolism
Permeability
Photosynthesis
Plant cells
Plants
Plants, Genetically Modified
Stomata
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Summary:Photosynthesis is often limited by the rate of CO₂ diffusion from the atmosphere to the chloroplast. The primary resistances for CO₂ diffusion are thought to be at the stomata and at photosynthesizing cells via a combination resulting from resistances of aqueous solution as well as the plasma membrane and both outer and inner chloroplast membranes. In contrast with stomatal resistance, the resistance of biological membranes to gas transport is not widely recognized as a limiting factor for metabolic function. We show that the tobacco (Nicotiana tabacum) plasma membrane and inner chloroplast membranes contain the aquaporin Nt AQP1. RNA interference-mediated decreases in Nt AQP1 expression lowered the CO₂ permeability of the inner chloroplast membrane. In vivo data show that the reduced amount of Nt AQP1 caused a 20% change in CO₂ conductance within leaves. Our discovery of CO₂ aquaporin function in the chloroplast membrane opens new opportunities for mechanistic examination of leaf internal CO₂ conductance regulation.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.107.054023