Improving plant stress tolerance and yield production: is the tonoplast aquaporin SlTIP2;2 a key to isohydric to anisohydric conversion?

Abstract

Summary• Anisohydric plants are thought to be more drought tolerant than isohydric plants. However, the molecular mechanism determining whether the plant water potential during the day remains constant or not regardless of the evaporative demand (isohydric vs anisohydric plant) is not known.• Here, it was hypothesized that aquaporins take part in this molecular mechanism determining the plant isohydric threshold. Using computational mining a key tonoplast aquaporin, tonoplast intrinsic protein 2;2 (SlTIP2;2), was selected within the large multifunctional gene family of tomato (Solanum lycopersicum) aquaporins based on its induction in response to abiotic stresses. SlTIP2;2-transformed plants (TOM-SlTIP2;2) were compared with controls in physiological assays at cellular and whole-plant levels.• Constitutive expression of SlTIP2;2 increased the osmotic water permeability of the cell and whole-plant transpiration. Under drought, these plants transpired more and for longer periods than control plants, reaching a lower relative water content, a behavior characterizing anisohydric plants. In 3-yr consecutive commercial glasshouse trials, TOM-SlTIP2;2 showed significant increases in fruit yield, harvest index and plant mass relative to the control under both normal and water-stress conditions.• In conclusion, it is proposed that the regulation mechanism controlling tonoplast water permeability might have a role in determining the whole-plant ishohydric threshold, and thus its abiotic stress tolerance.

Genotypic variation in transpiration of coppiced poplar during the third rotation of a short‐rotation bio‐energy culture

“…In the present study, the genotypes Koster and Bakan featured the typical water‐conserving behavior of the isohydric species, as the values of Ψ l did not change as much as those of g s over the course of the growing season. In isohydric plants, Ψ l does not vary much with changing levels of SWC or VPD, because these plants progressively close the stomata as a result of limited SWC or increased evaporative demand (e.g., maize (Tardieu, Zhang, & Gowing, 1993; Tardieu & Simonneau, 1998), tomato (Sade et al., 2009) and cowpea (Bates & Hall, 1981; Moreno, 2009)); water flow is tightly regulated by an effective stomatal control. In contrast, the behavior of genotype Grimminge was more in line with the anisohydric species, revealing a “risk‐taking” behavior, as the Ψ l decreased to maintain high the g s as SWC decreased or VPD increased over the course of the growing season.…”

The Grapevine Root-Specific Aquaporin VvPIP2;4N Controls Root Hydraulic Conductance and Leaf Gas Exchange under Well-Watered Conditions But Not under Water Stress

“…In the past decade, pioneering studies of overexpression or silencing of aquaporin genes were carried out in herbaceous model plants (for review, see Kaldenhoff et al, 2008). To date, with the exception of transgenic Eucalyptus species overexpressing a radish (Raphanus sativus) Plasma membrane Intrinsic Protein (PIP) aquaporin (Tsuchihira et al, 2010), reverse genetics studies have been performed in herbaceous species, such as Arabidopsis (Arabidopsis thaliana; Cui et al, 2008;Peng et al, 2008;Postaire et al, 2010), rice (Oryza sativa; Li et al, 2008;Matsumoto et al, 2009), tomato (Solanum lycopersicum; Sade et al, 2009), and tobacco (Nicotiana tabacum; Zhang et al, 2008). These plants, however, are not well suited for the task of assessing the role of aquaporins in complex processes of water transport and homeostasis, such as the transduction of hydraulic and nonhydraulic messages (Lovisolo et al, 2010) and the formation and recovery of embolisms (Secchi and Zwieniecki, 2010), which are typical of woody plants.…”

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

“…We compared R tomato plants in which the transcript level of the AQP gene SlTIP1;1 was up-regulated, R plants in which SlTIP1;1 had been silenced using Tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS), and a TYLCV-susceptible tomato genotype rendered TYLCV resistant by constitutive overexpression of the AQP gene SlTIP2;2. The results obtained with tomato were confirmed using an Arabidopsis mutant in which the endogenous AtTIP1;1 (the tomato ortholog; Sade et al, 2009;Reuscher et al, 2013) gene has been knocked out and transgenic Arabidopsis plants in which the tomato SlTIP2;2 gene was overexpressed. The results presented here indicate that TIP-AQPs are involved in TYLCV resistance, which is controlled by cellular water balance and transpiration, with subsequent effects on hormonal balance and sugar signaling.…”

“…According to comparisons of their amino acid sequences, all TIPs belong to a single phylogenetic group of tonoplast major intrinsic proteins, which includes four TIP subfamilies (TIP1-TIP4). Interestingly, although the expression of both SlTIP1;1 and SlTIP2;2 is affected by biotic stress in tomato (Eybishtz et al, 2009;Sade et al, 2009), these two genes are the most distantly related members of their subfamily (Reuscher et al, 2013).…”