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Alistair M Hetherington - One of the best experts on this subject based on the ideXlab platform.
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control of vacuolar dynamics and regulation of Stomatal Aperture by tonoplast potassium uptake
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Zaida Andres, Alistair M Hetherington, Javier Perezhormaeche, Eduardo O Leidi, Kathrin Schlucking, Leonie Steinhorst, Deirdre H Mclachlan, Karin Schumacher, Jorg Kudla, Beatriz CuberoAbstract:Stomatal movements rely on alterations in guard cell turgor. This requires massive K+ bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K+ into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells, the tonoplast-localized K+/H+ exchangers NHX1 and NHX2 are pivotal in the vacuolar accumulation of K+ and that nhx1 nhx2 mutant lines are dysfunctional in Stomatal regulation. Hypomorphic and complete-loss-of-function double mutants exhibited significantly impaired Stomatal opening and closure responses. Disruption of K+ accumulation in guard cells correlated with more acidic vacuoles and the disappearance of the highly dynamic remodelling of vacuolar structure associated with Stomatal movements. Our results show that guard cell vacuolar accumulation of K+ is a requirement for Stomatal opening and a critical component in the overall K+ homeostasis essential for Stomatal closure, and suggest that vacuolar K+ fluxes are also of decisive importance in the regulation of vacuolar dynamics and luminal pH that underlie Stomatal movements.
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abscisic acid induces oscillations in guard cell cytosolic free calcium that involve phosphoinositide specific phospholipase c
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: I Staxen, Christophe Pical, L T Montgomery, Alistair M Hetherington, Julie E Gray, Martin R. McainshAbstract:Oscillations in cytosolic free Ca2+ concentration ([Ca2+]cyt) are an important component of Ca2+-based signal transduction pathways. This fact has led us to investigate whether oscillations in [Ca2+]cyt are involved in the response of Stomatal guard cells to the plant hormone abscisic acid (ABA). We show that ABA induces oscillations in guard-cell [Ca2+]cyt. The pattern of the oscillations depended on the ABA concentration and correlated with the final Stomatal Aperture. We examined the mechanism by which ABA generates oscillations in guard-cell [Ca2+]cyt by using 1-(6-{[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione (U-73122), an inhibitor of phosphoinositide-specific phospholipase C (PI-PLC)-dependent processes in animals. U-73122 inhibited the hydrolysis of phosphatidylinositol 4,5-bisphosphate by a recombinant PI-PLC, isolated from a guard-cell-enriched cDNA library, in a dose-dependent manner. This result confirms that U-73122 is an inhibitor of plant PI-PLC activity. U-73122 inhibited both ABA-induced oscillations in [Ca2+]cyt and Stomatal closure. In contrast, U-73122 did not inhibit external Ca2+-induced oscillations in guard-cell [Ca2+]cyt and Stomatal closure. Furthermore, there was no effect of the inactive analogue 1-(6-{[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-2,5-pyrrolidinedione on recombinant PI-PLC activity or ABA-induced and external Ca2+-induced oscillations in [Ca2+]cyt and Stomatal closure. This lack of effect suggests that the effects of U-73122 in guard cells are the result of inhibition of PI-PLC and not a consequence of nonspecific effects. Taken together, our data suggest a role for PI-PLC in the generation of ABA-induced oscillations in [Ca2+]cyt and point toward the involvement of oscillations in [Ca2+]cyt in the maintenance of Stomatal Aperture by ABA.
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changes in Stomatal behavior and guard cell cytosolic free calcium in response to oxidative stress
Plant Physiology, 1996Co-Authors: Martin R. Mcainsh, H Clayton, T. A. Mansfield, Alistair M HetheringtonAbstract:We have investigated the cellular basis for the effects of oxidative stress on Stomatal behavior using Stomatal bioassay and ratio photometric techniques. Two oxidative treatments were employed in this study: (a) methyl viologen, which generates superoxide radicals, and (b) H2O2. Both methyl viologen and H2O2 inhibited Stomatal opening and promoted Stomatal closure. At concentrations [less than or equal to]10-5 M, the effects of methyl viologen and H2O2 on Stomatal behavior were reversible and were abolished by 2 mM EGTA or 10 [mu]M verapamil. In addition, at 10-5 M, i.e. the maximum concentration at which the effects of the treatments were prevented by EGTA or verapamil, methyl viologen and H2O2 caused an increase in guard cell cytosolic free Ca2+ ([Ca2+]i), which was abolished in the presence of EGTA. Therefore, at low concentrations of methyl viologen and H2O2, removal of extracellular Ca2+ prevented both the oxidative stress-induced changes in Stomatal Aperture and the associated increases in [Ca2+]i. This suggests that in this concentration range the effects of the treatments are Ca2+-dependent and are mediated by changes in [Ca2+]i. In contrast, at concentrations of methyl viologan and H2O2 > 10-5 M, EGTA and verapamil had no effect. However, in this concentration range the effects of the treatments were irreversible and correlated with a marked reduction in membrane integrity and guard cell viability. This suggests that at high concentrations the effects of methyl viologen and H2O2 may be due to changes in membrane integrity. The implications of oxidative stress-induced increases in [Ca2+]i and the possible disruption of guard-cell Ca2+ homeostasis are discussed in relation to the processes of Ca2+-based signal transduction in Stomatal guard cells and the control of Stomatal Aperture.
Martin R. Mcainsh - One of the best experts on this subject based on the ideXlab platform.
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abscisic acid induces oscillations in guard cell cytosolic free calcium that involve phosphoinositide specific phospholipase c
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: I Staxen, Christophe Pical, L T Montgomery, Alistair M Hetherington, Julie E Gray, Martin R. McainshAbstract:Oscillations in cytosolic free Ca2+ concentration ([Ca2+]cyt) are an important component of Ca2+-based signal transduction pathways. This fact has led us to investigate whether oscillations in [Ca2+]cyt are involved in the response of Stomatal guard cells to the plant hormone abscisic acid (ABA). We show that ABA induces oscillations in guard-cell [Ca2+]cyt. The pattern of the oscillations depended on the ABA concentration and correlated with the final Stomatal Aperture. We examined the mechanism by which ABA generates oscillations in guard-cell [Ca2+]cyt by using 1-(6-{[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione (U-73122), an inhibitor of phosphoinositide-specific phospholipase C (PI-PLC)-dependent processes in animals. U-73122 inhibited the hydrolysis of phosphatidylinositol 4,5-bisphosphate by a recombinant PI-PLC, isolated from a guard-cell-enriched cDNA library, in a dose-dependent manner. This result confirms that U-73122 is an inhibitor of plant PI-PLC activity. U-73122 inhibited both ABA-induced oscillations in [Ca2+]cyt and Stomatal closure. In contrast, U-73122 did not inhibit external Ca2+-induced oscillations in guard-cell [Ca2+]cyt and Stomatal closure. Furthermore, there was no effect of the inactive analogue 1-(6-{[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-2,5-pyrrolidinedione on recombinant PI-PLC activity or ABA-induced and external Ca2+-induced oscillations in [Ca2+]cyt and Stomatal closure. This lack of effect suggests that the effects of U-73122 in guard cells are the result of inhibition of PI-PLC and not a consequence of nonspecific effects. Taken together, our data suggest a role for PI-PLC in the generation of ABA-induced oscillations in [Ca2+]cyt and point toward the involvement of oscillations in [Ca2+]cyt in the maintenance of Stomatal Aperture by ABA.
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changes in Stomatal behavior and guard cell cytosolic free calcium in response to oxidative stress
Plant Physiology, 1996Co-Authors: Martin R. Mcainsh, H Clayton, T. A. Mansfield, Alistair M HetheringtonAbstract:We have investigated the cellular basis for the effects of oxidative stress on Stomatal behavior using Stomatal bioassay and ratio photometric techniques. Two oxidative treatments were employed in this study: (a) methyl viologen, which generates superoxide radicals, and (b) H2O2. Both methyl viologen and H2O2 inhibited Stomatal opening and promoted Stomatal closure. At concentrations [less than or equal to]10-5 M, the effects of methyl viologen and H2O2 on Stomatal behavior were reversible and were abolished by 2 mM EGTA or 10 [mu]M verapamil. In addition, at 10-5 M, i.e. the maximum concentration at which the effects of the treatments were prevented by EGTA or verapamil, methyl viologen and H2O2 caused an increase in guard cell cytosolic free Ca2+ ([Ca2+]i), which was abolished in the presence of EGTA. Therefore, at low concentrations of methyl viologen and H2O2, removal of extracellular Ca2+ prevented both the oxidative stress-induced changes in Stomatal Aperture and the associated increases in [Ca2+]i. This suggests that in this concentration range the effects of the treatments are Ca2+-dependent and are mediated by changes in [Ca2+]i. In contrast, at concentrations of methyl viologan and H2O2 > 10-5 M, EGTA and verapamil had no effect. However, in this concentration range the effects of the treatments were irreversible and correlated with a marked reduction in membrane integrity and guard cell viability. This suggests that at high concentrations the effects of methyl viologen and H2O2 may be due to changes in membrane integrity. The implications of oxidative stress-induced increases in [Ca2+]i and the possible disruption of guard-cell Ca2+ homeostasis are discussed in relation to the processes of Ca2+-based signal transduction in Stomatal guard cells and the control of Stomatal Aperture.
Hannes Kollist - One of the best experts on this subject based on the ideXlab platform.
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Rapid Responses to Abiotic Stress: Priming the Landscape for the Signal Transduction Network
Trends in Plant Science, 2018Co-Authors: Hannes Kollist, Jaakko Kangasjärvi, Soham Sengupta, Maris Nuhkat, Sara I Zandalinas, Ron MittlerAbstract:Plants grow and reproduce within a highly dynamic environment that can see abrupt changes in conditions, such as light intensity, temperature, humidity, or interactions with biotic agents. Recent studies revealed that plants can respond within seconds to some of these conditions, engaging many different metabolic and molecular networks, as well as rapidly altering their Stomatal Aperture. Some of these rapid responses were further shown to propagate throughout the entire plant via waves of reactive oxygen species (ROS) and Ca2+ that are possibly mediated through the plant vascular system. Here, we propose that the integration of these signals is mediated through pulses of gene expression that are coordinated throughout the plant in a systemic manner by the ROS/Ca+2 waves.
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defense related transcription factors wrky70 and wrky54 modulate osmotic stress tolerance by regulating Stomatal Aperture in arabidopsis
New Phytologist, 2013Co-Authors: Jing Li, Hannes Kollist, Sebastien Besseau, Petri Toronen, Nina Sipari, Liisa Holm, Tapio E PalvaAbstract:WRKY transcription factors (TFs) have been mainly associated with plant defense, but recent studies have suggested additional roles in the regulation of other physiological processes. Here, we explored the possible contribution of two related group III WRKY TFs, WRKY70 and WRKY54, to osmotic stress tolerance. These TFs are positive regulators of plant defense, and co-operate as negative regulators of salicylic acid (SA) biosynthesis and senescence. We employed single and double mutants of wrky54 and wrky70, as well as a WRKY70 overexpressor line, to explore the role of these TFs in osmotic stress (polyethylene glycol) responses. Their effect on gene expression was characterized by microarrays and verified by quantitative PCR. Stomatal phenotypes were assessed by water retention and Stomatal conductance measurements. The wrky54wrky70 double mutants exhibited clearly enhanced tolerance to osmotic stress. However, gene expression analysis showed reduced induction of osmotic stress-responsive genes in addition to reduced accumulation of the osmoprotectant proline. By contrast, the enhanced tolerance was correlated with improved water retention and enhanced Stomatal closure. These findings demonstrate that WRKY70 and WRKY54 co-operate as negative regulators of Stomatal closure and, consequently, osmotic stress tolerance in Arabidopsis, suggesting that they have an important role, not only in plant defense, but also in abiotic stress signaling. Keywords: abscisic acid (ABA), Arabidopsis, gene regulation, osmotic stress, salicylic acid (SA), stomata, WRKY transcription factor Introduction In their natural environment, plants are confronted with a series of biotic and abiotic stresses that detrimentally affect their growth and development. Among these, osmotic stress, which results in cellular water deficit, is one of the most limiting factors of plant growth, distribution and crop productivity, and consequently poses a serious threat to the agricultural industry worldwide (Rabbani et al., 2003). The disruption of plant water status and low water potential can be caused by a number of factors, such as decreased water availability in the soil during drought, reduced water uptake as a result of high salinity or freeze-induced cellular dehydration (Verslues et al., 2006). To respond to osmotic stress, plants have evolved complex adaptive strategies that help to avoid or tolerate cellular dehydration, allowing plants to grow and complete their life cycles. The first response of a plant is the control of water balance by Stomatal movement. At the cellular level, tolerance to osmotic stress includes enhanced expression of stress-responsive genes and metabolic adjustments, resulting in the accumulation of osmolytes, protective solutes and proteins (Xiong et al., 1999; Verslues et al., 2006; Shinozaki & Yamaguchi-Shinozaki, 2007). The central phytohormone in osmotic stress perception and signaling is abscisic acid (ABA), which has been implicated in both the control of Stomatal Aperture and the activation of a distinct set of genes associated with the biosynthesis of osmolytes and protective proteins (Mahajan & Tuteja, 2005; Shinozaki & Yamaguchi-Shinozaki, 2007; Acharya & Assmann, 2009; Hao et al., 2011). Recent advances have succeeded in the identification of PYR/PYL/RCAR ABA receptors which interact with type 2C protein phosphatases (PP2Cs), such as ABI1, HAB1 and AIP1 (Leung et al., 1994; Meyer et al., 1994; Saez et al., 2004; Ma et al., 2009; Park et al., 2009; Lim et al., 2012). The binding of ABA to these cytosolic receptors inactivates the inhibition of PP2Cs on downstream signal transduction, allowing protein kinases, such as SnRK2s, to activate ABF/AREB bZIP transcription factors (TFs) (Umezawa et al., 2009; Santiago et al., 2012). These TFs have a pivotal function during osmotic stress for the induction of ABA-responsive genes (Uno et al., 2000; Antoni et al., 2011; Fujita et al., 2013). In guard cells, ABA perception and PP2C sequestration allow SnRK2s and several calcium-dependent protein kinases (CDPKs) to activate NADPH oxidase and anion channels (SLAC1 and SLAH3) for guard cell closure (Joshi-Saha et al., 2011). The TFs induced or activated by plant perception of environmental cues are central mediators of transcriptional reprograming which leads to plant adaptation (Chen et al., 2002; Nakashima et al., 2009). In addition to ABF/AREB bZIP TFs, members of several other TF families have been found to regulate the expression of ABA-, drought- or cold-responsive genes, including MYB, MYC, NAC and WRKY TFs (Abe et al., 2003; Fujita et al., 2004; Rushton et al., 2012). The WRKY TF family with > 70 members in Arabidopsis is one of the central TF groups involved in biotic stress responses (Ulker & Somssich, 2004; Yamasaki et al., 2005). WRKY genes are typically induced by pathogens and salicylic acid (SA), and, in turn, control the expression of defense-related genes (Dong et al., 2003; Ulker & Somssich, 2004). WRKYs have also been implicated in various other physiological and developmental programs, including senescence, seed germination and trichome development (Robatzek & Somssich, 2001; Johnson et al., 2002; Seki et al., 2002; Singh et al., 2002; Besseau et al., 2012). Recent studies, especially in Arabidopsis and rice, have indicated that some WRKY TFs also play important roles in transcriptional reprograming during abiotic stresses, such as drought, high salinity, cold and osmotic stress (Chen et al., 2012). In this context, WRKYs have been implicated in ABA signaling and the oxidative stress response (Chen et al., 2010; Rushton et al., 2012). For example, AtWRKY40 can inhibit directly the expression of important ABA-responsive genes and can function as a negative regulator of ABA signaling in seed germination, in a complex interacting network with the antagonists AtWRKY18 and AtWRKY60 (Chen et al., 2010; Shang et al., 2010). However, AtWRKY63 (ABO3) has been shown to regulate seed germination and seedling growth, and appears to be involved in the control of Stomatal closure, consequently affecting the drought tolerance of the plant (Ren et al., 2010). This function in the abiotic stress response is highlighted by the capacity of WRKY40 and WRKY63 to bind directly to the promoters of ABA-responsive ABF/AREB TF genes (Ren et al., 2010; Shang et al., 2010). Two members of Arabidopsis WRKY group III, the closely related WRKY54 and WRKY70 TFs, have been demonstrated to be key components in the regulation of biotic stress response networks integrating signals from SA and jasmonic acid (JA) pathways in plant defense and in the control of SA biosynthesis (Li et al., 2004, 2006; Wang et al., 2006). Furthermore, co-operation of WRKY70 and WRKY54 as negative regulators of leaf senescence in Arabidopsis has also been demonstrated (Ulker et al., 2007; Besseau et al., 2012). In this study, we explored the possible role of WRKY54 and WRKY70 in abiotic stress tolerance, in particular in adaptation to osmotic stress. We found that wrky54wrky70 double mutant exhibited enhanced tolerance to osmotic stress. We characterized the involvement of these two WRKYs in the regulation of osmotic stress-related genes and elucidated their potential role in osmotic stress adaptation. Our results suggest that WRKY54 and WRKY70 co-operate to modulate Stomatal movement and osmotic stress-responsive gene expression through both SA-mediated and SA-independent processes, highlighting the complexity of plant responses to environmental cues and the interactions of signaling networks in plant stress responses.
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arabidopsis pyr pyl rcar receptors play a major role in quantitative regulation of Stomatal Aperture and transcriptional response to abscisic acid
The Plant Cell, 2012Co-Authors: Miguel Gonzalezguzman, Gaston A Pizzio, Regina Antoni, Francisco Verasirera, Ebe Merilo, George W Bassel, Maria A Fernandez, Michael J Holdsworth, Miguel A Perezamador, Hannes KollistAbstract:Abscisic acid (ABA) is a key hormone for plant growth, development, and stress adaptation. Perception of ABA through four types of receptors has been reported. We show here that impairment of ABA perception through the PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR) branch reduces vegetative growth and seed production and leads to a severe open stomata and ABA-insensitive phenotype, even though other branches for ABA perception remain functional. An Arabidopsis thaliana sextuple mutant impaired in six PYR/PYL receptors, namely PYR1, PYL1, PYL2, PYL4, PYL5, and PYL8, was able to germinate and grow even on 100 μM ABA. Whole-rosette Stomatal conductance (Gst) measurements revealed that leaf transpiration in the sextuple pyr/pyl mutant was higher than in the ABA-deficient aba3-1 or ABA-insensitive snrk2.6 mutants. The gradually increasing Gst values of plants lacking three, four, five, and six PYR/PYLs indicate quantitative regulation of Stomatal Aperture by this family of receptors. The sextuple mutant lacked ABA-mediated activation of SnRK2s, and ABA-responsive gene expression was dramatically impaired as was reported in snrk2.2/2.3/2.6. In summary, these results show that ABA perception by PYR/PYLs plays a major role in regulation of seed germination and establishment, basal ABA signaling required for vegetative and reproductive growth, Stomatal Aperture, and transcriptional response to the hormone.
Ron Mittler - One of the best experts on this subject based on the ideXlab platform.
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Phytochrome B Is Required for Systemic Stomatal Responses and Reactive Oxygen Species Signaling during Light Stress.
Plant physiology, 2020Co-Authors: Amith R. Devireddy, Emmanuel Liscum, Ron MittlerAbstract:Perception of a change in light intensity leads to the activation of multiple physiological, metabolic, and molecular responses in plants. These responses allow acclimation to fluctuating light conditions, e.g. sunflecks in field grown plants, preventing cellular damage associated with excess light stress. Perception of light stress by a single Arabidopsis (Arabidopsis thaliana) leaf was recently shown to activate different local and systemic responses that include rapid changes in Stomatal Aperture size; these were found to be coordinated by a systemic process of reactive oxygen species (ROS)-derived ROS production (i.e. the ROS wave). How light intensity is perceived, and how long the ROS wave stays "on" during this process are, however, unknown. Here we show that triggering of the ROS wave by a local excess light stress treatment results in the induction and maintenance of high levels of systemic ROS for up to 6 h. Despite these high systemic ROS levels, Stomatal Aperture size returns to control size within 3 h, and the systemic Stomatal response can be retriggered within 6 h. These findings suggest that the ROS wave triggers a systemic stress memory mechanism that lasts for 3 to 6 h, but that within 3 h of its activation, stomata become insensitive to ROS and open. We further show that the excess light stress-triggered ROS wave, as well as the excess light stress-triggered local and systemic Stomatal Aperture closure responses, are dependent on phytochrome B function. Our findings reveal a delicate interplay between excess light stress, phytochrome B, ROS production, and rapid systemic Stomatal responses.
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Rapid Responses to Abiotic Stress: Priming the Landscape for the Signal Transduction Network
Trends in Plant Science, 2018Co-Authors: Hannes Kollist, Jaakko Kangasjärvi, Soham Sengupta, Maris Nuhkat, Sara I Zandalinas, Ron MittlerAbstract:Plants grow and reproduce within a highly dynamic environment that can see abrupt changes in conditions, such as light intensity, temperature, humidity, or interactions with biotic agents. Recent studies revealed that plants can respond within seconds to some of these conditions, engaging many different metabolic and molecular networks, as well as rapidly altering their Stomatal Aperture. Some of these rapid responses were further shown to propagate throughout the entire plant via waves of reactive oxygen species (ROS) and Ca2+ that are possibly mediated through the plant vascular system. Here, we propose that the integration of these signals is mediated through pulses of gene expression that are coordinated throughout the plant in a systemic manner by the ROS/Ca+2 waves.
Yucheng Wang - One of the best experts on this subject based on the ideXlab platform.
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an arabidopsis zinc finger protein increases abiotic stress tolerance by regulating sodium and potassium homeostasis reactive oxygen species scavenging and osmotic potential
Frontiers in Plant Science, 2016Co-Authors: Dandan Zang, Wenhui Zhang, Yiming Zhang, Xinxin Shi, Yucheng WangAbstract:Plant zinc finger proteins (ZFPs) comprise a large protein family and they mainly involve in abiotic stress tolerance. Although Arabidopsis RING/FYVE/PHD ZFP (At5g62460; AtRZFP) is found to bind to zinc, whether it is involved in abiotic stress tolerance is unknown. In the present study, we characterized the roles of AtRZFP in response to abiotic stresses. The expression of AtRZFP was induced significantly by salt and osmotic stress. AtRZFP positively mediates tolerance to salt and osmotic stress. Additionally, compared with wild-type Arabidopsis plants, plants overexpressing AtRZFP showed reduced reactive oxygen species accumulation, enhanced superoxide dismutase and peroxidase activity, increased soluble sugars and proline contents, reduced K+ loss, decreased Na+ accumulation, Stomatal Aperture and the water loss rate. Conversely, AtRZFP knockout plants displayed the opposite physiological changes when exposed to salt or osmotic stress conditions. These data suggested that AtRZFP enhances salt and osmotic tolerance through a series of physiological processes, including enhanced reactive oxygen species scavenging, maintaining Na+ and K+ homeostasis, controlling the Stomatal Aperture to reduce the water loss rate, and accumulating soluble sugars and proline to adjust the osmotic potential.
