Differential tissue-specific expression of NtAQP1 in Arabidopsis thaliana reveals a role for this protein in stomatal and mesophyll conductance of CO2 under standard and salt-stress conditions
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The regulation of plant hydraulic conductance and gas conductance involves a number of different morphological, physiological and molecular mechanisms working in harmony. At the molecular level, aquaporins play a key role in the transport of water, as well as CO2, through cell membranes. Yet, their tissue-related function, which controls whole-plant gas exchange and water relations, is less understood. In this study, we examined the tissue-specific effects of the stress-induced tobacco Aquaporin1 (NtAQP1), which functions as both a water and CO2 channel, on whole-plant behavior. In tobacco and tomato plants, constitutive overexpression of NtAQP1 increased net photosynthesis (A N), mesophyll CO2 conductance (g m) and stomatal conductance (g s) and, under stress, increased root hydraulic conductivity (L pr) as well. Our results revealed that NtAQP1 that is specifically expressed in the mesophyll tissue plays an important role in increasing both A N and g m. Moreover, targeting NtAQP1 expression to the cells of the vascular envelope significantly improved the plants’ stress response. Surprisingly, NtAQP1 expression in the guard cells did not have a significant effect under any of the tested conditions. The tissue-specific involvement of NtAQP1 in hydraulic and gas conductance via the interaction between the vasculature and the stomata is discussed.
KeywordsArabidopsis Mesophyll conductance Nicotiana tabacum aquaporin 1 Salt stress Stomatal conductance Tissue-specific expression
Artificial xylem sap
Substomatal CO2 concentration
Leaf mesophyll conductance for CO2
Leaf hydraulic conductivity
Root hydraulic conductivity
Green fluorescent protein
This study was supported by a grant from the Rehovot-Hohenheim partnership program and the Israel Science Foundation, Jerusalem (ISF; Grant # 1311/12) to MM. JF acknowledges the support of Plan Nacional (Spain) project grant MECOME (BFU2011-23294). We thank Dr. Orit Edelbaum and Professor Shmuel Wolf (Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University of Jerusalem, Rehovot, Israel), Dr. Einat Sadot and Dr. Mohamad Abu-Abied (Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel), Professor Yuval Eshed (Department of Plant Sciences, Weizmann Institute of Science, Rehovot, Israel) and Professor Ralf Kaldenhoff (Department of Biology, Applied Plant Sciences, Technische Universität Darmstadt, Darmstadt, Germany) for supplying the different constructs and plant materials. Eduard Belausov (Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel) helped with microscopy imaging.
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