The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Menachem Moshelion - One of the best experts on this subject based on the ideXlab platform.
-
stress is basic aba alkalinizes both the xylem sap and the cytosol of arabidopsis vascular Bundle Sheath Cells by inhibiting their p type h atpase and stimulating their v type h atpase
bioRxiv, 2021Co-Authors: Tanmayee Torne, Menachem Moshelion, Yael Grunwald, Adi Yaaran, Ahan Dalal, Nava MoranAbstract:BACKGROUND AND HYPOTHESIS* Under water deprivation, in many perennial species, the stress hormone, ABA, appears in the xylem sap in the shoot (including leaf) veins and the xylem sap pH (pHEXT) increases. This study aimed to test the hypothesis that ABA is the signal for an altered proton balance of the leaf-vein-enwrapping Bundle Sheath Cells (BSCs). METHODS* Plant Material. We used a few Arabidopsis thaliana (L.) Heynh. genotypes: wildtype (WT) of two accessions, Landsberg erecta (Ler) and Columbia (Col), and a few mutants and transformants in these backgrounds. * H+-Pumps activities. We monitored ABA effects on the H+-pump activities in the BSCs cytosol-delimiting membranes (plasma membrane and tonoplast) by monitoring the cytosol and the xylem pH, and the membrane potential (EM), by imaging the fluorescence of pH- and membrane potential (EM)-reporting probes: (a) the BSCs pHEXT - with the ratiometric fluorescent dye FITC-dextran petiole-fed into detached leaves in unbuffered xylem perfusion solution (XPS), (b) the BSCs pHCYT - with the ratiometric dye SNARF1 loaded into BSCs isolated protoplasts, and (c) the BSCs EM - with the ratiometric dye di- 8-ANEPPS. RESULTS* ABA increased the pHEXT; this response was abolished in an abi1-1 mutant with impaired signaling via a PP2C (ABI1) and in an aha2-4 mutant with knocked-down AHA2; * ABA depolarized the WT BSCs; * ABA increased pHCYT irrespective of AHA2 activity (i.e., whether or not AHA was inhibited by vanadate, or in the aha2-4 mutant); * The ABA-induced cytosol alkalinization was abolished in the absence of VHA activity (i.e., when VHA was inhibited by bafilomycin A1, or in the vha-a2 vha-a3 double mutant with inactive VHA); * All these results resemble the ABA effect on GCs; * In contrast to GCs, AHA2 and not AHA1 is the ABA major target in BSCs; * Blue light (BL) enabled the response of the BSCs VHA to ABA; * The ABA- and BL-signaling pathways acting on both BSCs pumps, AHA2 and VHA, are likely to be BSCs autonomous, based on (a) the presence in the BSCs of many genes of the ABA- and BL-signaling pathways and (b) ABA responses (depolarization and pHCYT elevation) demonstrated under BL in isolated protoplasts. SIGNIFICANCE STATEMENTWe reveal here an alkalinizing effect of the plant drought-stress hormone ABA on the pH on both sides of the plasmalemma of the vein-enwrapping Bundle Sheath Cells (BSCs), due to ABA inhibition of the BSCs AHA2, the plasmalemma H+- ATPase and stimulation of VHA, their vacuolar H+-ATPase. Since pH affects the BSCs selective regulation of solute and water fluxes into the leaf, these H+- pumps may be attractive targets for manipulations aiming to improve plant drought response.
-
Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+ -ATPase of vascular Bundle Sheath Cells.
The Plant journal : for cell and molecular biology, 2021Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Nava Moran, Sanbon Chaka Gosa, Menachem MoshelionAbstract:The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates the xylem-sap pH and leaf radial water fluxes. We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem-sap pH and the leaf hydraulic conductance (Kleaf ), and the effect of pH on the water osmotic permeability (Pf ) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf . Conversely, AHA2 knockdown which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf , and elevating external pH to 7.5 decreased the BSCs Pf . All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance. Supporting Information.
-
arabidopsis leaf hydraulic conductance is regulated by xylem sap ph controlled in turn by a p type h atpase of vascular Bundle Sheath Cells
bioRxiv, 2020Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by their h atpase open by xylem acidification closed by xylem alkalinization
bioRxiv, 2019Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH using the ratiometric fluorescent probe FITC-dextran fed into veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH, the whole leaf hydraulic conductance (Kleaf) and the water osmotic permeability of isolated BSCs protoplasts (Pf). Our results demonstrated AHA2 indispensability for xylem-sap acidification, necessary, in turn, for elevating Pf and Kleaf. Conversely, elevating xylem-sap pH to 7.5, reduced significantly both Pf and Kleaf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf water influx. This positions the BSCs as a pH-controlled transpiration valve in series with the stomata. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by an h atpase via xylem acidification
bioRxiv, 2018Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute a selective and dynamic barrier to solutes and water. The over three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase2) transcript we recently reported in Arabidopsis BSCs (compared to mesophyll Cells) suggests AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically, while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves, demonstrated AHA2 indispensability for low sap pH, resolving the decades-lasting controversy about the molecular origin of xylem sap acidification. Furthermore, both AHA2 activity and sap acidification by added buffers enhanced the hydraulic leaf conductance, while alkaline sap pH - buffered or in AHA2 knockouts - reduced it. Similarly, the osmotic water permeability of isolated BSC protoplasts was reduced by alkaline and enhanced by acidic pH, thereby revealing the cellular mechanism underlying the above causative link between AHA2 activity and leaf water influx. This positions the BSCs as a transpiration-controlling valve in series with the stomata.
Yael Grunwald - One of the best experts on this subject based on the ideXlab platform.
-
stress is basic aba alkalinizes both the xylem sap and the cytosol of arabidopsis vascular Bundle Sheath Cells by inhibiting their p type h atpase and stimulating their v type h atpase
bioRxiv, 2021Co-Authors: Tanmayee Torne, Menachem Moshelion, Yael Grunwald, Adi Yaaran, Ahan Dalal, Nava MoranAbstract:BACKGROUND AND HYPOTHESIS* Under water deprivation, in many perennial species, the stress hormone, ABA, appears in the xylem sap in the shoot (including leaf) veins and the xylem sap pH (pHEXT) increases. This study aimed to test the hypothesis that ABA is the signal for an altered proton balance of the leaf-vein-enwrapping Bundle Sheath Cells (BSCs). METHODS* Plant Material. We used a few Arabidopsis thaliana (L.) Heynh. genotypes: wildtype (WT) of two accessions, Landsberg erecta (Ler) and Columbia (Col), and a few mutants and transformants in these backgrounds. * H+-Pumps activities. We monitored ABA effects on the H+-pump activities in the BSCs cytosol-delimiting membranes (plasma membrane and tonoplast) by monitoring the cytosol and the xylem pH, and the membrane potential (EM), by imaging the fluorescence of pH- and membrane potential (EM)-reporting probes: (a) the BSCs pHEXT - with the ratiometric fluorescent dye FITC-dextran petiole-fed into detached leaves in unbuffered xylem perfusion solution (XPS), (b) the BSCs pHCYT - with the ratiometric dye SNARF1 loaded into BSCs isolated protoplasts, and (c) the BSCs EM - with the ratiometric dye di- 8-ANEPPS. RESULTS* ABA increased the pHEXT; this response was abolished in an abi1-1 mutant with impaired signaling via a PP2C (ABI1) and in an aha2-4 mutant with knocked-down AHA2; * ABA depolarized the WT BSCs; * ABA increased pHCYT irrespective of AHA2 activity (i.e., whether or not AHA was inhibited by vanadate, or in the aha2-4 mutant); * The ABA-induced cytosol alkalinization was abolished in the absence of VHA activity (i.e., when VHA was inhibited by bafilomycin A1, or in the vha-a2 vha-a3 double mutant with inactive VHA); * All these results resemble the ABA effect on GCs; * In contrast to GCs, AHA2 and not AHA1 is the ABA major target in BSCs; * Blue light (BL) enabled the response of the BSCs VHA to ABA; * The ABA- and BL-signaling pathways acting on both BSCs pumps, AHA2 and VHA, are likely to be BSCs autonomous, based on (a) the presence in the BSCs of many genes of the ABA- and BL-signaling pathways and (b) ABA responses (depolarization and pHCYT elevation) demonstrated under BL in isolated protoplasts. SIGNIFICANCE STATEMENTWe reveal here an alkalinizing effect of the plant drought-stress hormone ABA on the pH on both sides of the plasmalemma of the vein-enwrapping Bundle Sheath Cells (BSCs), due to ABA inhibition of the BSCs AHA2, the plasmalemma H+- ATPase and stimulation of VHA, their vacuolar H+-ATPase. Since pH affects the BSCs selective regulation of solute and water fluxes into the leaf, these H+- pumps may be attractive targets for manipulations aiming to improve plant drought response.
-
Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+ -ATPase of vascular Bundle Sheath Cells.
The Plant journal : for cell and molecular biology, 2021Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Nava Moran, Sanbon Chaka Gosa, Menachem MoshelionAbstract:The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates the xylem-sap pH and leaf radial water fluxes. We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem-sap pH and the leaf hydraulic conductance (Kleaf ), and the effect of pH on the water osmotic permeability (Pf ) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf . Conversely, AHA2 knockdown which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf , and elevating external pH to 7.5 decreased the BSCs Pf . All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance. Supporting Information.
-
arabidopsis leaf hydraulic conductance is regulated by xylem sap ph controlled in turn by a p type h atpase of vascular Bundle Sheath Cells
bioRxiv, 2020Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by their h atpase open by xylem acidification closed by xylem alkalinization
bioRxiv, 2019Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH using the ratiometric fluorescent probe FITC-dextran fed into veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH, the whole leaf hydraulic conductance (Kleaf) and the water osmotic permeability of isolated BSCs protoplasts (Pf). Our results demonstrated AHA2 indispensability for xylem-sap acidification, necessary, in turn, for elevating Pf and Kleaf. Conversely, elevating xylem-sap pH to 7.5, reduced significantly both Pf and Kleaf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf water influx. This positions the BSCs as a pH-controlled transpiration valve in series with the stomata. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by an h atpase via xylem acidification
bioRxiv, 2018Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute a selective and dynamic barrier to solutes and water. The over three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase2) transcript we recently reported in Arabidopsis BSCs (compared to mesophyll Cells) suggests AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically, while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves, demonstrated AHA2 indispensability for low sap pH, resolving the decades-lasting controversy about the molecular origin of xylem sap acidification. Furthermore, both AHA2 activity and sap acidification by added buffers enhanced the hydraulic leaf conductance, while alkaline sap pH - buffered or in AHA2 knockouts - reduced it. Similarly, the osmotic water permeability of isolated BSC protoplasts was reduced by alkaline and enhanced by acidic pH, thereby revealing the cellular mechanism underlying the above causative link between AHA2 activity and leaf water influx. This positions the BSCs as a transpiration-controlling valve in series with the stomata.
Marshall D. Hatch - One of the best experts on this subject based on the ideXlab platform.
-
Adenosine 5'-triphosphate-mediated activation of sucrose-phosphate synthase in Bundle Sheath Cells of C4 plants
Planta, 1997Co-Authors: John E. Lunn, Robert T. Furbank, Marshall D. HatchAbstract:We report the ATP-mediated activation of sucrose-phosphate synthase in Bundle Sheath Cells prepared from C4 species. Sucrose synthesis was followed by measuring the incorporation of [14C]fructose 6-phosphate into sucrose in Bundle Sheath Cells also provided with uridine 5′-diphosphoglucose (UDPGlc). Studies with Panicum miliaceum L. Cells showed that activation was largely due to an increase in the affinity for UDPGlc and was therefore only evident at limiting UDPGlc concentrations. The apparent K m UDPGlc for sucrose synthesis by Cells pretreated and assayed with ATP was about 0.7 mM compared with 7–8 mM for control Cells without ATP. The γ-thio derivative of ATP had a similar effect to ATP. The effect was also evident when ATP was rapidly removed from Cells prior to assay. Sucrose-phosphate synthase activity in extracts from Cells pretreated with or without ATP showed similar differences in K m UDPGlc. These observations support the view that ATP is inducing a covalent modification of the enzyme. However, several protein kinase inhibitors did not prevent activation. Changes of more than threefold were observed for the K m UDPGlc with sucrose-phosphate synthase extracted from Bundle Sheath Cells rapidly isolated from attached leaves that were subjected to dark/light treatments. The possible relationship between these changes and those induced by ATP with isolated Cells is discussed.
-
Measurement of the Leakage of CO2 from Bundle-Sheath Cells of Leaves during C4 Photosynthesis
Plant physiology, 1995Co-Authors: Marshall D. Hatch, Anthony Agostino, Colin L. D. JenkinsAbstract:During C4 photosynthesis, CO2 is released in Bundle-Sheath Cells by decarboxylation of C4 acids and then refixed via ribulose-1,5-bisphosphate carboxylase. In this study we examined the efficiency of this process by determining the proportion of the released CO2 that diffuses back to mesophyll Cells instead of being refixed. This leak of CO2 was assessed by determining the amount of 14CO2 released from leaves during a chase in high [12CO2] following a 70-s pulse in 14CO2. A computer-based analysis of the time-course curve for 14CO2 release indicated a first-order process and provided an estimate of the initial velocity of 14CO2 release from leaves. From this value and the net rate of photosynthesis determined from the 14CO2 fixed in the pulse, the CO2 leak rate from Bundle-Sheath Cells (expressed as a percentage of the rate of CO2 production from C4 acids) could be deduced. For nine species of Gramineae representing the different subgroups of C4 plants and two NAD-malic enzyme-type dicotyledonous species, the CO2 leak ranged between 8 and 14%. However, very high CO2 leak rates (averaging about 27%) were recorded for two NADP-malic enzyme-type dicotyledonous species of Flaveria. The results are discussed in terms of the efficiency of C4 photosynthesis and observed quantum yields.
Noa Wigoda - One of the best experts on this subject based on the ideXlab platform.
-
Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+ -ATPase of vascular Bundle Sheath Cells.
The Plant journal : for cell and molecular biology, 2021Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Nava Moran, Sanbon Chaka Gosa, Menachem MoshelionAbstract:The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates the xylem-sap pH and leaf radial water fluxes. We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem-sap pH and the leaf hydraulic conductance (Kleaf ), and the effect of pH on the water osmotic permeability (Pf ) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf . Conversely, AHA2 knockdown which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf , and elevating external pH to 7.5 decreased the BSCs Pf . All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance. Supporting Information.
-
arabidopsis leaf hydraulic conductance is regulated by xylem sap ph controlled in turn by a p type h atpase of vascular Bundle Sheath Cells
bioRxiv, 2020Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by their h atpase open by xylem acidification closed by xylem alkalinization
bioRxiv, 2019Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH using the ratiometric fluorescent probe FITC-dextran fed into veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH, the whole leaf hydraulic conductance (Kleaf) and the water osmotic permeability of isolated BSCs protoplasts (Pf). Our results demonstrated AHA2 indispensability for xylem-sap acidification, necessary, in turn, for elevating Pf and Kleaf. Conversely, elevating xylem-sap pH to 7.5, reduced significantly both Pf and Kleaf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf water influx. This positions the BSCs as a pH-controlled transpiration valve in series with the stomata. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by an h atpase via xylem acidification
bioRxiv, 2018Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute a selective and dynamic barrier to solutes and water. The over three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase2) transcript we recently reported in Arabidopsis BSCs (compared to mesophyll Cells) suggests AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically, while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves, demonstrated AHA2 indispensability for low sap pH, resolving the decades-lasting controversy about the molecular origin of xylem sap acidification. Furthermore, both AHA2 activity and sap acidification by added buffers enhanced the hydraulic leaf conductance, while alkaline sap pH - buffered or in AHA2 knockouts - reduced it. Similarly, the osmotic water permeability of isolated BSC protoplasts was reduced by alkaline and enhanced by acidic pH, thereby revealing the cellular mechanism underlying the above causative link between AHA2 activity and leaf water influx. This positions the BSCs as a transpiration-controlling valve in series with the stomata.
-
Bundle Sheath Cells are internal leaf water valves controlled via xylem acidification by h atpase
bioRxiv, 2017Co-Authors: Noa Wigoda, Yael Grunwald, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute selective and dynamic barrier to solutes and water. The over-three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase 2) transcript we reported recently in the Arabidopsis BSCs (compared to mesophyll Cells) suggested AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves demonstrated AHA2 necessity for low sap pH. AHA2 activity or sap acidification by buffers enhanced the hydraulic leaf conductance, while alkaline sap pH buffered or in AHA2 knockouts reduced it. These results resolve the decades-lasting enigma about the molecular origin of xylem sap acidification and demonstrate AHA2 importance for controlling leaf water influx.
Nir Sade - One of the best experts on this subject based on the ideXlab platform.
-
Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+ -ATPase of vascular Bundle Sheath Cells.
The Plant journal : for cell and molecular biology, 2021Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Nava Moran, Sanbon Chaka Gosa, Menachem MoshelionAbstract:The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates the xylem-sap pH and leaf radial water fluxes. We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem-sap pH and the leaf hydraulic conductance (Kleaf ), and the effect of pH on the water osmotic permeability (Pf ) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf . Conversely, AHA2 knockdown which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf , and elevating external pH to 7.5 decreased the BSCs Pf . All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance. Supporting Information.
-
arabidopsis leaf hydraulic conductance is regulated by xylem sap ph controlled in turn by a p type h atpase of vascular Bundle Sheath Cells
bioRxiv, 2020Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by their h atpase open by xylem acidification closed by xylem alkalinization
bioRxiv, 2019Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Abstract The leaf vascular Bundle Sheath Cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll Cells. Under normal conditions, xylem-sap pH of We monitored the xylem-sap pH using the ratiometric fluorescent probe FITC-dextran fed into veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH, the whole leaf hydraulic conductance (Kleaf) and the water osmotic permeability of isolated BSCs protoplasts (Pf). Our results demonstrated AHA2 indispensability for xylem-sap acidification, necessary, in turn, for elevating Pf and Kleaf. Conversely, elevating xylem-sap pH to 7.5, reduced significantly both Pf and Kleaf. All these demonstrate a causative link between AHA2 activity in BSCs and leaf water influx. This positions the BSCs as a pH-controlled transpiration valve in series with the stomata. One-sentence summary Bundle-Sheath Cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH
-
Bundle Sheath Cells are leaf water valves controlled by an h atpase via xylem acidification
bioRxiv, 2018Co-Authors: Yael Grunwald, Noa Wigoda, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute a selective and dynamic barrier to solutes and water. The over three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase2) transcript we recently reported in Arabidopsis BSCs (compared to mesophyll Cells) suggests AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically, while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves, demonstrated AHA2 indispensability for low sap pH, resolving the decades-lasting controversy about the molecular origin of xylem sap acidification. Furthermore, both AHA2 activity and sap acidification by added buffers enhanced the hydraulic leaf conductance, while alkaline sap pH - buffered or in AHA2 knockouts - reduced it. Similarly, the osmotic water permeability of isolated BSC protoplasts was reduced by alkaline and enhanced by acidic pH, thereby revealing the cellular mechanism underlying the above causative link between AHA2 activity and leaf water influx. This positions the BSCs as a transpiration-controlling valve in series with the stomata.
-
Bundle Sheath Cells are internal leaf water valves controlled via xylem acidification by h atpase
bioRxiv, 2017Co-Authors: Noa Wigoda, Yael Grunwald, Nir Sade, Adi Yaaran, Tanmayee Torne, Sanbon Chaka Gosa, Nava Moran, Menachem MoshelionAbstract:Bundle-Sheath Cells (BSCs), parenchymatous Cells tightly enwrapping the leaf veins, constitute selective and dynamic barrier to solutes and water. The over-three-fold-higher abundance of the AHA2 (Arabidopsis H+-ATPase 2) transcript we reported recently in the Arabidopsis BSCs (compared to mesophyll Cells) suggested AHA2 participation in this barrier function. Manipulating AHA2 activity in BSCs pharmacologically and genetically while monitoring the xylem sap pH by fluorescence imaging of FITC-dextran fed into veins of detached leaves demonstrated AHA2 necessity for low sap pH. AHA2 activity or sap acidification by buffers enhanced the hydraulic leaf conductance, while alkaline sap pH buffered or in AHA2 knockouts reduced it. These results resolve the decades-lasting enigma about the molecular origin of xylem sap acidification and demonstrate AHA2 importance for controlling leaf water influx.
