The Role of Tobacco Aquaporin1 in Improving Water Use Efficiency, Hydraulic Conductivity, and Yield Production Under Salt Stress      

Abstract

Tobacco (Nicotiana tabacum; C3) plants increase their water use efficiency (WUE) under abiotic stress and are suggested to show characteristics of C4 photosynthesis in stems, petioles, and transmitting tract cells. The tobacco stress-induced Aquaporin1 (NtAQP1) functions as both water and CO 2 channel. In tobacco plants, overexpression of NtAQP1 increases leaf net photosynthesis (A N ), mesophyll CO 2 conductance, and stomatal conductance, whereas its silencing reduces root hydraulic conductivity (L p ). Nevertheless, interaction between NtAQP1 leaf and root activities and its impact on plant WUE and productivity under normal and stress conditions have never been suggested. Thus, the aim of this study was to suggest a role for NtAQP1 in plant WUE, stress resistance, and productivity. Expressing NtAQP1 in tomato (Solanum lycopersicum) plants (TOM-NtAQP1) resulted in higher stomatal conductance, whole-plant transpiration, and A N under all conditions tested. In contrast to controls, where, under salt stress, L p decreased more than 3-fold, TOM-NtAQP1 plants, similar to maize (Zea mays; C4) plants, did not reduce L p dramatically (only by approximately 40%). Reciprocal grafting provided novel evidence for NtAQP1's role in preventing hydraulic failure and maintaining the whole-plant transpiration rate. Our results revealed independent, albeit closely related, NtAQP1 activities in roots and leaves. This dual activity, which increases the plant's water use and A N under optimal and stress conditions, resulted in improved WUE. Consequently, it contributed to the plant's stress resistance in terms of yield production under all tested conditions, as demonstrated in both tomato and Arabidopsis (Arabidopsis thaliana) plants constitutively expressing NtAQP1. The putative involvement of NtAQP1 in tobacco's C4-like photosynthesis characteristics is discussed.

Aquaporins Contribute to ABA-Triggered Stomatal Closure through OST1-Mediated Phosphorylation

“…The aquaporin blocker mercury (HgCl 2 ) was shown to alter stomatal aperture in Vicia faba (Yang et al, 2006), but this effect has not been reproduced (Shope and Mott, 2006) and can be questioned because of mercury cellular toxicity. Finally, steady state changes in stomatal conductance have been reported in plants with genetically altered aquaporin functions (Hanba et al, 2004;Flexas et al, 2006;Cui et al, 2008;Sade et al, 2010). Yet, these changes could reflect a genuine function of aquaporins in stomata or altered water or CO 2 transport (Flexas et al, 2006) in other leaf tissues.…”

Water Balance, Hormone Homeostasis, and Sugar Signaling Are All Involved in Tomato Resistance toTomato Yellow Leaf Curl Virus

“…The specific role of TIP-AQPs was demonstrated by overexpressing another Solanaceae AQP that localizes to the plasma membrane and not the tonoplast. Overexpression of this AQP, Nicotiana tabacum AQP1 (NtAQP1), was previously reported to improve tomato plant abiotic stress tolerance (these mutant tomato plants were referred to as Tom-NtAQP; Sade et al, 2010). Here, these Tom-NtAQP1 plants did not show any resistance to TYLCV upon inoculation (Supplemental Fig.…”

“…Plant AQPs are involved in regulating both transpiration and hydraulic conductivity (Aharon et al, 2003;Boursiac et al, 2005;Postaire et al, 2010;Pou et al, 2013). Differential levels of AQP expression correlate with differences in the rate of leaf transpiration under normal and abiotic/ biotic stress conditions (Siefritz et al, 2002;Parent et al, 2009;Sade et al, 2010Sade et al, , 2012b.…”

Mammalian androgen stimulates photosynthesis in drought-stressed soybean

“…Arabidopsis plants with a reduced expression of genes encoding aquaporins PIP1 and 2 after the withdrawal of drought showed a reduced transpiration and turgor recovering difficulties [33]. Under optimal conditions and salt stress, tobacco plants overexpressing the aquaporin gene NtAQP1 had increased water use and increased net photosynthesis [34]. It has been shown that gene expression of aquaporins in plants occurs in the early stages of seed germination [35].…”