A hydraulic signal in root‐to‐shoot signalling of water shortage

Christmann, Alexander; Weiler, Elmar W.; Steudle, Ernst; Grill, Erwin

doi:10.1111/j.1365-313x.2007.03234.x

Cited by 483 publications

(368 citation statements)

References 45 publications

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“…In these plants, ABA is produced via the residual activity of defective enzymes (Rock and Zeevaart, 1991) or via minor ABA biosynthetic pathways hypothesized to exist in higher plants (North et al, 2007). With regard to the location of ABA synthesis, shoots are the main source of ABA in the plant, as found in grafting studies (Holbrook et al, 2002;Christmann et al, 2007;McAdam et al, 2016a) and also supported by gene expression data (Ernst et al, 2010;Boursiac et al, 2013;Kuromori et al, 2014). The leaf-borne ABA is synthesized mainly in the phloem companion cells of the vasculature (Endo et al, 2008;Kuromori et al, 2014).…”

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confidence: 59%

Stomatal VPD Response: There Is More to the Story Than ABA

et al. 2017

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Guard cells shrink and close stomatal pores when air humidity decreases (i.e. when the difference between the vapor pressures of leaf and atmosphere [VPD] increases). The role of abscisic acid (ABA) in VPD-induced stomatal closure has been studied using ABA-related mutants that respond to VPD in some studies and not in others. The importance of ABA biosynthesis in guard cells versus vasculature for whole-plant stomatal regulation is unclear as well. Here, we show that Arabidopsis (Arabidopsis thaliana) lines carrying mutations in different steps of ABA biosynthesis as well as pea (Pisum sativum) wilty and tomato (Solanum lycopersicum) flacca ABA-deficient mutants had higher stomatal conductance compared with wild-type plants. To characterize the role of ABA production in different cells, we generated transgenic plants where ABA biosynthesis was rescued in guard cells or phloem companion cells of an ABA-deficient mutant. In both cases, the whole-plant stomatal conductance, stunted growth phenotype, and leaf ABA level were restored to wild-type values, pointing to the redundancy of ABA sources and to the effectiveness of leaf ABA transport. All ABA-deficient lines closed their stomata rapidly and extensively in response to high VPD, whereas plants with mutated protein kinase OST1 showed stunted VPD-induced responses. Another strongly ABAinsensitive mutant, defective in the six ABA PYR/RCAR receptors, responded to changes in VPD in both directions strongly and symmetrically, indicating that its VPD-induced closure could be passive hydraulic. We discuss that both the VPD-induced passive hydraulic stomatal closure and the stomatal VPD regulation of ABA-deficient mutants may be conditional on the initial pretreatment stomatal conductance.

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Stomatal VPD Response: There Is More to the Story Than ABA

et al. 2017

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“…Therefore, ABA-GE was proposed to be a rootto-shoot signaling molecule. However, under drought stress, ABA-mediated stomatal closure occurs independently of root ABA biosynthesis (Christmann et al, 2007). Thus, the involvement of ABA-GE in root-to-shoot signaling of water stress conditions remains to be revealed (Goodger and Schachtman, 2010).…”

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confidence: 99%

Vacuolar Transport of Abscisic Acid Glucosyl Ester Is Mediated by ATP-Binding Cassette and Proton-Antiport Mechanisms in Arabidopsis

et al. 2013

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Abscisic acid (ABA) is a key plant hormone involved in diverse physiological and developmental processes, including abiotic stress responses and the regulation of stomatal aperture and seed germination. Abscisic acid glucosyl ester (ABA-GE) is a hydrolyzable ABA conjugate that accumulates in the vacuole and presumably also in the endoplasmic reticulum. Deconjugation of ABA-GE by the endoplasmic reticulum and vacuolar b-glucosidases allows the rapid formation of free ABA in response to abiotic stress conditions such as dehydration and salt stress. ABA-GE further contributes to the maintenance of ABA homeostasis, as it is the major ABA catabolite exported from the cytosol. In this work, we identified that the import of ABA-GE into vacuoles isolated from Arabidopsis (Arabidopsis thaliana) mesophyll cells is mediated by two distinct membrane transport mechanisms: proton gradientdriven and ATP-binding cassette (ABC) transporters. Both systems have similar K m values of approximately 1 mM. According to our estimations, this low affinity appears nevertheless to be sufficient for the continuous vacuolar sequestration of ABA-GE produced in the cytosol. We further demonstrate that two tested multispecific vacuolar ABCC-type ABC transporters from Arabidopsis exhibit ABA-GE transport activity when expressed in yeast (Saccharomyces cerevisiae), which also supports the involvement of ABC transporters in ABA-GE uptake. Our findings suggest that the vacuolar ABA-GE uptake is not mediated by specific, but rather by several, possibly multispecific, transporters that are involved in the general vacuolar sequestration of conjugated metabolites.

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“…The stomatal aperture was correlated with the ABA content in the xylem sap, suggesting that ABA synthesized in roots was transported to leaves via the xylem to induce stomatal closure. Nevertheless, it appears that ABA transport from roots to leaves is not always required for stomatal closure, because reciprocal grafting between WT and ABA-deficient mutants showed that leaf genotypes, but not root genotypes, were correlated with leaf stomatal conductance (12,13).…”

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Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor

Kanno

Hanada

Chiba

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

429

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Movement of the plant hormone abscisic acid (ABA) within plants has been documented; however, the molecular mechanisms that regulate ABA transport are not fully understood. By using a modified yeast two-hybrid system, we screened Arabidopsis cDNAs capable of inducing interactions between the ABA receptor PYR/PYL/ RCAR and PP2C protein phosphatase under low ABA concentrations. By using this approach, we identified four members of the NRT1/PTR family as candidates for ABA importers. Transport assays in yeast and insect cells demonstrated that at least one of the candidates ABA-IMPORTING TRANSPORTER (AIT) 1, which had been characterized as the low-affinity nitrate transporter NRT1.2, mediates cellular ABA uptake. Compared with WT, the ait1/nrt1.2 mutants were less sensitive to exogenously applied ABA during seed germination and/or postgermination growth, whereas overexpression of AIT1/NRT1.2 resulted in ABA hypersensitivity in the same conditions. Interestingly, the inflorescence stems of ait1/ nrt1.2 had a lower surface temperature than those of the WT because of excess water loss from open stomata. We detected promoter activities of AIT1/NRT1.2 around vascular tissues in inflorescence stems, leaves, and roots. These data suggest that the function of AIT1/NRT1.2 as an ABA importer at the site of ABA biosynthesis is important for the regulation of stomatal aperture in inflorescence stems.guard cells | liquid chromatography-tandem mass spectrometry | water stress

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A hydraulic signal in root‐to‐shoot signalling of water shortage

Cited by 483 publications

References 45 publications

Stomatal VPD Response: There Is More to the Story Than ABA

Stomatal VPD Response: There Is More to the Story Than ABA

Vacuolar Transport of Abscisic Acid Glucosyl Ester Is Mediated by ATP-Binding Cassette and Proton-Antiport Mechanisms in Arabidopsis

Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor

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