Drought and Abscisic Acid Effects on Aquaporin Content Translate into Changes in Hydraulic Conductivity and Leaf Growth Rate: A Trans-Scale Approach

INRA, UMR 759 Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, F-34060 Montpellier, France.
Plant physiology (Impact Factor: 6.84). 03/2009; 149(4):2000-12. DOI: 10.1104/pp.108.130682
Source: PubMed

ABSTRACT The effects of abscisic acid (ABA) on aquaporin content, root hydraulic conductivity (Lpr), whole plant hydraulic conductance, and leaf growth are controversial. We addressed these effects via a combination of experiments at different scales of plant organization and tested their consistency via a model. We analyzed under moderate water deficit a series of transformed maize (Zea mays) lines, one sense and three antisense, affected in NCED (for 9-cis-epoxycarotenoid dioxygenase) gene expression and that differed in the concentration of ABA in the xylem sap. In roots, the mRNA expression of most aquaporin PIP (for plasma membrane intrinsic protein) genes was increased in sense plants and decreased in antisense plants. The same pattern was observed for the protein contents of four PIPs. This resulted in more than 6-fold differences between lines in Lpr under both hydrostatic and osmotic gradients of water potential. This effect was probably due to differences in aquaporin activity, because it was nearly abolished by a hydrogen peroxide treatment, which blocks the water channel activity of aquaporins. The hydraulic conductance of intact whole plants was affected in the same way when measured either in steady-state conditions or via the rate of recovery of leaf water potential after rewatering. The recoveries of leaf water potential and elongation upon rehydration differed between lines and were accounted for by the experimentally measured Lpr in a model of water transfer. Overall, these results suggest that ABA has long-lasting effects on plant hydraulic properties via aquaporin activity, which contributes to the maintenance of a favorable plant water status.

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Available from: B. Parent, Sep 28, 2015
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    • "The phytohormone ABA plays a critical role in increasing water abstraction by the roots (Setter 1996). First, ABA increases water movement from the roots to foliar parts by adjusting hydraulic conductance among plant tissues (Zhang et al. 1995, Parent et al. 2009). Secondly, ABA affects root growth depending on the tissue water status (Dalal et al. 2009, Yamaguchi et al. 2010). "
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    ABSTRACT: Lowland rice (Nipponbare) and upland rice (Gaoshan 1) that are comparable under normal and moderate drought conditions showed dramatic differences in severe drought conditions, including natural-occurring long-term drought and simulated rapid water deficits. We focused on their root response and found that enhanced tolerance of upland rice to severe drought conditions was mainly due to the lower level of ABA in its roots than that in the lowland rice. We firstly excluded the effect of ABA biosynthesis and catabolism on root-accumulated ABA levels in both rice by monitoring the expressions of four OsNCED genes and two OsABA8ox genes. Next, we excluded the impact of the aerial parts on roots by suppressing leaf-biosynthesized ABA with fluridone and NDGA (nordihydroguaiaretic acid) and measuring ABA level in detached roots. Instead, we proved that upland rice had the ability to export considerably more root-sourced ABA than lowland rice under severe drought, which improved ABA-dependent drought adaptation. The investigation of apoplastic pH in root cell and root anatomy evidenced that ABA leakage in the root system of upland rice was related to high apoplastic pH and the absence of Casparian bands in the sclerenchyma layer. Finally, taking some genes as examples, we predicted that different ABA levels in rice roots stimulated distinct ABA perception and signaling cascades, which influenced its response to water stress. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For Permissions, please e-mail:
    Plant and Cell Physiology 03/2015; 56(5). DOI:10.1093/pcp/pcv022 · 4.93 Impact Factor
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    • "It is probable that during the dark the ABA in the leaves has been transported from the roots, instead of having been synthesized in the leaves. Supporting this is the observation that ABA in the xylem increases the hydraulic conductivity, which is important for rehydration during darkness (Parent et al., 2009). ABA production in leaves could then be reduced to keep the ABA content constant. "
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    ABSTRACT: To conserve water plants close the stomata in response to increased abscisic acid (ABA) content. Previous studies have shown that plants developed in high relative air humidity (RH>85%) develop malfunctioning stomata and have lower ABA content. It has therefore been hypothesized that low ABA content during development results in malfunctioning stomata. In this study the stomatal functioning of Arabidopsis thaliana was evaluated and the content, biosynthesis and catabolism of ABA were quantified. It was found that even though they have lower ABA content during growth, plants developed under high RH were able to produce large amounts of ABA in detached leaves, but still had high water loss. Plants developed in high RH had increased ABA 8‘hydroxylase activity of cytochrome P450CYP707A. Also, plants developed in high RH that were sprayed with ABA or Abscinazole-E1, which inhibits the ABA 8‘hydroxylase activity, had reduced stomatal apertures. ABA deficient mutants had higher water loss in detached leaves than wild type plants in both high and moderate RH. From these results we therefore conclude that continuous low ABA content in high RH is due to increased ABA catabolism by the ABA 8‘hydroxylase activity of cytochrome P450CYP707A. The continuous low ABA content result in reduced ability to close the stomata.
    Environmental and Experimental Botany 02/2015; 115. DOI:10.1016/j.envexpbot.2015.02.004 · 3.36 Impact Factor
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    • "Under abiotic stress, water uptake occurs mainly through the " cell-to-cell " pathway, which is considered to be regulated by aquaporin activity (Boursiac et al., 2005; Horie et al., 2011; Sutka et al., 2011). Aquaporin activity is affected by a number of stimuli, including ABA, ethylene, Ca 2+ , and reactive oxygen species (Parent et al., 2009; Hu et al., 2012; Azad et al., 2004; Boursiac et al., 2008a). It has been reported that under short-term salt stress, H 2 O 2 can decrease the activity of aquaporin by direct oxidant gating, regulating the phosphorylation status, and inducing the relocalization of aquaporin, which leads to decreased water uptake (Boursiac et al., 2008a,b). "
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    ABSTRACT: It has been widely reported that silicon (Si) improves the resistance of plants to salt stress. Most of the previous studies have examined how silicon prevents Na+ uptake, but the performance and underlying mechanism through which silicon alleviates salt-induced osmotic stress has been largely ignored. In the present study, the mechanism through which Si alleviates salt-induced osmotic stress was investigated using sorghum in a hydroponic system. Si had no effect on seedling growth under normal conditions. Under salt stress, the photosynthesis and transpiration rate were decreased, but these decreases were alleviated by Si application. In addition, the leaf water content and leaf elongation rate were maintained at higher levels with Si than without Si. The root hydraulic conductance (Lp) of the seedlings were inhibited by salt, but Si application alleviated this inhibition. Under salt stress, the transpiration rates of the seedlings both with and without Si were decreased to the same level by HgCl2 treatment and partially rescued by β-mercaptoethanol treatment, suggesting that aquaporin was responsible for the alleviation of the decrease in Lp. Moreover, transcript levels of several aquaporin genes were upregulated by Si. Under salt stress, Si inhibited the increase in the root H2O2 levels and enhanced the activities of antioxidant enzymes. Moreover, similar to Si, pre-treatment with catalase alleviated the decrease in the transpiration rate, indicating that Si enhanced aquaporin activity by reducing H2O2 accumulation. These results indicate that under short-term salt stress, Si application can alleviate the decrease in Lp by mediating aquaporin activity, leading to increased water uptake and resistance to salt-induced osmotic stress.
    Environmental and Experimental Botany 02/2015; 111:42-51. DOI:10.1016/j.envexpbot.2014.10.006 · 3.36 Impact Factor
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