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Disappearance of PIN1 after NO treatment and comparison of cue1 and pin1 root phenotypes. (A) Distribution of PIN1 pro :GFP-PIN1 protein is shown in untreated control plants (C), in plants treated with the NO scavenger cPTIO (1 mM; 8 h), and in plants treated with the NO donors SNP (100 μM; 3, 8, and 24 h), SNAP (1 mM; 24 h), or GSNO (1 mM; 24 h), with or without the proteasome inhibitor MG132 (100 μM; 24 h). Root tissues were stained with propidium iodide. (B) Immunoblot analysis with anti-GFP antiserum of in vivo levels of PIN1 protein in root extracts of PIN1 pro :GFP-PIN1 seedlings, in the absence or presence of NO donors and scavengers together with MG132. Actin protein levels also were determined as a loading control. (C) Confocal images of the PIN1 pro :GFP-PIN1 line in the cue1 background. (D) Confocal images after mPS-PI staining. (E and F) Root meristem size (E) and primary root length (n = 25) (F) of roots from WT (Col-0) and cue1-and pin1 −/− -mutant seedlings grown for 7 d on MS agar plates. A minimum of 8-10 roots per genotype was analyzed. Asterisks indicate significant differences compared with WT (P < 0.05).
Source publication
Nitric oxide (NO) is considered a key regulator of plant developmental processes and defense, although the mechanism and direct targets of NO action remain largely unknown. We used phenotypic, cellular, and genetic analyses in Arabidopsis thaliana to explore the role of NO in regulating primary root growth and auxin transport. Treatment with the NO...
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... and 48 h after treatment (Fig. 4A). The NO scavenger cPTIO partially rescued the depletion of DR5 pro :GUS expression in roots treated with SNP (Fig. 4B). Similar to the expression pattern of DR5 pro : GUS in the pin1 mutant (Fig. 4B), the DR5 pro :GUS/GFP spatial pattern was altered in cue1/nox1 mutants, where endogenous NO levels are enhanced (Fig. 4C and Fig. S5), clearly estab- lishing that increasing NO accumulation depletes auxin-de- pendent reporter expression in the apical auxin maximum. This alteration of auxin-dependent response in the meristematic zone is different from that produced by application of the auxin transport inhibitor napthylphthalamic acid (NPA) (Fig. ...
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... radiolabeled auxin in cue1/nox1, supporting the hypothesis that enhanced NO levels in this mutant background cause a defect in acropetal indoleacetic acid (IAA) transport capacity. We also examined fluorescence of GFP fusions to the auxin efflux carriers PIN1 and PIN2 in the presence of the NO donors SNP, SNAP, and GSNO and the NO scavenger cPTIO (Fig. 5A and Fig. S6). Confocal time-course analysis showed that PIN1-GFP fluorescence was decreased clearly in the stele and primary root meristem upon treatment with the NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti- GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO ...
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... Fig. S6). Confocal time-course analysis showed that PIN1-GFP fluorescence was decreased clearly in the stele and primary root meristem upon treatment with the NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti- GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO donors (Fig. 5B). In agreement with these results, PIN1 pro :GFP-PIN1 fluorescence clearly was reduced in genetic backgrounds where endogenous NO levels are enhanced (Fig. 5C), consistent with the conclusion that increases of NO levels reduce PIN1 levels. Interestingly, PIN1 levels were not altered significantly in lat- eral root primordia after ...
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... NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti- GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO donors (Fig. 5B). In agreement with these results, PIN1 pro :GFP-PIN1 fluorescence clearly was reduced in genetic backgrounds where endogenous NO levels are enhanced (Fig. 5C), consistent with the conclusion that increases of NO levels reduce PIN1 levels. Interestingly, PIN1 levels were not altered significantly in lat- eral root primordia after treatment with cPTIO or SNP or in the cue1/nox1-mutant background, suggesting that regulation of PIN1 levels by NO is restricted exclusively to the primary root ...
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... showed that PIN1 transcript levels were not altered significantly after treatment with the NO donor SNP or by mutations in CUE1/NOX1 (Fig. S7). To determine if PIN1 protein was degraded by the proteasome after NO treat- ment, we treated PIN1 pro :GFP-PIN1 seedlings with the known proteasome inhibitor MG132, both in the presence and absence of NO (Fig. 5 A and B). PIN1 and PIN2 levels in MG132-treated plants did not differ significantly from that in untreated plants or in plants treated with the NO scavenger cPTIO (Fig. 5 A and B and Fig. S6). Interestingly, PIN1 pro :GFP-PIN1 plants treated both with an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in ...
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... was degraded by the proteasome after NO treat- ment, we treated PIN1 pro :GFP-PIN1 seedlings with the known proteasome inhibitor MG132, both in the presence and absence of NO (Fig. 5 A and B). PIN1 and PIN2 levels in MG132-treated plants did not differ significantly from that in untreated plants or in plants treated with the NO scavenger cPTIO (Fig. 5 A and B and Fig. S6). Interestingly, PIN1 pro :GFP-PIN1 plants treated both with an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in plants treated only with the NO donor. Furthermore, using immunoblot analysis with anti-GFP antiserum, we could not detect changes in the accu- mulation of PIN1 ...
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... an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in plants treated only with the NO donor. Furthermore, using immunoblot analysis with anti-GFP antiserum, we could not detect changes in the accu- mulation of PIN1 in NO-treated PIN1 pro :GFP-PIN1 seedlings after the 26S proteasome was inhibited by MG132 (Fig. 5B). Therefore, we propose that the PIN1 level is regulated by NO and that high levels of endogenous or applied NO promote reductions in PIN1 protein levels by a proteasome-independent mechanism. To analyze further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth ...
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... PIN1 level is regulated by NO and that high levels of endogenous or applied NO promote reductions in PIN1 protein levels by a proteasome-independent mechanism. To analyze further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO do- nors and the cue1/nox mutant. ...
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... further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO do- nors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hy- persensitive phenotype under low concentrations of SNAP (200 μM) ...
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... in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO do- nors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hy- persensitive phenotype under low concentrations of SNAP (200 μM) (Fig. S8). Conversely, supplying exogenous ...
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... root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO do- nors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hy- persensitive phenotype under low concentrations of SNAP (200 μM) (Fig. S8). Conversely, supplying exogenous auxin (IAA or Fig. 3. The effect of NO on ...
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... application of the NO donor (SNP) or the use of cue1/nox1-mutant background] attenuates auxin- dependent reporter expression in the QC and CSC. The auxin- induced maximum gene expression in the root apex, which is necessary for meristem maintenance, is normally observed in these cells, but this maximum is diminished in the presence of elevated NO (Fig. 4 and Fig. S5) (29). Additionally, we found that NO reduces the frequency of cell division in the root apex as judged by expression of the mitotic marker CycB1;1 pro :GUS-DB (Fig. S4) and that chronically high NO levels eventually cause meristem collapse. Taken together with the several lines of evi- dence that support the hypothesis that perturbing ...
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... process of root organogenesis is controlled by auxin (30,32,33). Our data confirm that high levels of endogenous or applied NO specifically attenuate auxin response (Fig. 4 and Fig. S5). In- terestingly, conditional loss of function of ABP1, a key regulator for auxin-mediated responses (34), and NO show similar effects on the root meristem, exhibiting arrest of cell division and elongated cells next to partially collapsed root meristems. Similarly, the phenotypes of the pin1 mutant (30), impaired in the regulation of ...
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... mutant in regards to the or- ganization of the QC/CSC and starch accumulation. Our results suggest that polar auxin transport is impacted negatively by over- accumulation of NO because PIN1 protein levels are reduced dramatically after delivery of exogenous NO and in the cue1/nox1 background, which produces increased endogenous NO levels (Fig. 5). Consistent with the PIN1 disappearance with NO expo- sure, the pin1 mutant is not resistant to NO. Because qRT-PCR analysis revealed that PIN1 expression is not influenced by NO (Fig. S7), we hypothesized that the disappearance of PIN1 protein may be regulated posttranslationally. The MG132 proteasome- specific inhibitor was used to ...
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... also examined fluorescence of GFP fusions to the auxin efflux carriers PIN1 and PIN2 in the presence of the NO donors SNP, SNAP, and GSNO and the NO scavenger cPTIO (Fig. 5A and Fig. S6). Confocal time-course analysis showed that PIN1-GFP fluorescence was decreased clearly in the stele and primary root meristem upon treatment with the NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti-GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO ...
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... Fig. S6). Confocal time-course analysis showed that PIN1-GFP fluorescence was decreased clearly in the stele and primary root meristem upon treatment with the NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti-GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO donors (Fig. 5B). In agreement with these results, PIN1 pro :GFP-PIN1 fluorescence clearly was reduced in genetic backgrounds where endogenous NO levels are enhanced (Fig. 5C), consistent with the conclusion that increases of NO levels reduce PIN1 levels. Interestingly, PIN1 levels were not altered significantly in lateral root primordia after ...
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... NO donors SNP, SNAP, and GSNO. Using immunoblot analysis with anti-GFP antiserum, we also detected a reduction of GFP protein in PIN1 pro :GFP-PIN1 seedlings after treatment with NO donors (Fig. 5B). In agreement with these results, PIN1 pro :GFP-PIN1 fluorescence clearly was reduced in genetic backgrounds where endogenous NO levels are enhanced (Fig. 5C), consistent with the conclusion that increases of NO levels reduce PIN1 levels. Interestingly, PIN1 levels were not altered significantly in lateral root primordia after treatment with cPTIO or SNP or in the cue1/nox1-mutant background, suggesting that regulation of PIN1 levels by NO is restricted exclusively to the primary root (Fig. ...
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... showed that PIN1 transcript levels were not altered significantly after treatment with the NO donor SNP or by mutations in CUE1/NOX1 (Fig. S7). To determine if PIN1 protein was degraded by the proteasome after NO treatment, we treated PIN1 pro :GFP-PIN1 seedlings with the known proteasome inhibitor MG132, both in the presence and absence of NO (Fig. 5 A and B). PIN1 and PIN2 levels in MG132-treated plants did not differ significantly from that in untreated plants or in plants treated with the NO scavenger cPTIO (Fig. 5 A and B and Fig. S6). Interestingly, PIN1 pro :GFP-PIN1 plants treated both with an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in ...
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... was degraded by the proteasome after NO treatment, we treated PIN1 pro :GFP-PIN1 seedlings with the known proteasome inhibitor MG132, both in the presence and absence of NO (Fig. 5 A and B). PIN1 and PIN2 levels in MG132-treated plants did not differ significantly from that in untreated plants or in plants treated with the NO scavenger cPTIO (Fig. 5 A and B and Fig. S6). Interestingly, PIN1 pro :GFP-PIN1 plants treated both with an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in plants treated only with the NO donor. Furthermore, using immunoblot analysis with anti-GFP antiserum, we could not detect changes in the accumulation of PIN1 in ...
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... an NO donor (SNP or SNAP) and with MG132 displayed a low GFP signal not different from that in plants treated only with the NO donor. Furthermore, using immunoblot analysis with anti-GFP antiserum, we could not detect changes in the accumulation of PIN1 in NO-treated PIN1 pro :GFP-PIN1 seedlings after the 26S proteasome was inhibited by MG132 (Fig. 5B). Therefore, we propose that the PIN1 level is regulated by NO and that high levels of endogenous or applied NO promote reductions in PIN1 protein levels by a proteasome-independent mechanism. To analyze further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth ...
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... PIN1 level is regulated by NO and that high levels of endogenous or applied NO promote reductions in PIN1 protein levels by a proteasome-independent mechanism. To analyze further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO donors and the cue1/nox mutant. Interestingly, ...
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... further the relevance of PIN1 reductions in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO donors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hypersensitive phenotype under low concentrations of SNAP (200 μM) ...
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... in root responses to NO, we analyzed the root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO donors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hypersensitive phenotype under low concentrations of SNAP (200 μM) (Fig. S8). Conversely, supplying exogenous auxin ...
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... root phenotype of pin1 mutants under standard growth conditions and in response to NO donors (Fig. 5 D-F and Fig. S8). The distorted organization of the QC, surrounding cells, and CSC of the NO-overproducing cue1/nox1 mutant is similar to that of pin1 mutants (Fig. 5D). Additionally, the root meristem size (Fig. 5E) and total primary root length (Fig. 5F) of pin1 mutants resembles plants treated with NO donors and the cue1/nox mutant. Interestingly, pin1 mutants do not display a visible NO-resistant phenotype, instead exhibiting a hypersensitive phenotype under low concentrations of SNAP (200 μM) (Fig. S8). Conversely, supplying exogenous auxin (IAA or Fig. 3. The effect of NO on ...
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... cue1/nox1 mutant in regards to the organization of the QC/CSC and starch accumulation. Our results suggest that polar auxin transport is impacted negatively by overaccumulation of NO because PIN1 protein levels are reduced dramatically after delivery of exogenous NO and in the cue1/nox1 background, which produces increased endogenous NO levels (Fig. 5). Consistent with the PIN1 disappearance with NO exposure, the pin1 mutant is not resistant to NO. Because qRT-PCR analysis revealed that PIN1 expression is not influenced by NO (Fig. S7), we hypothesized that the disappearance of PIN1 protein may be regulated posttranslationally. The MG132 proteasomespecific inhibitor was used to ...
Citations
... In tobacco leaves, the application of NO donors affects the expression of cytokinin-responsive genes, indicating that NO signaling can modulate cytokinin response pathways (Tun et al. 2001). This modulation by NO is also evident in processes like root growth, where high levels of NO can antagonize cytokinin signaling, thereby affecting root development (Fernández-Marcos et al. 2011). ...
Plant cell walls are dynamic structures that play crucial roles in growth, development, and stress responses. Despite our growing understanding of cell wall biology, the connections between cell wall integrity (CWI) and cell cycle progression in plants remain poorly understood. This review aims to explore the intricate relationship between CWI and cell cycle progression in plants, drawing insights from studies in yeast and mammals. We provide an overview of the plant cell cycle, highlight the role of endoreplication in cell wall composition, and discuss recent findings on the molecular mechanisms linking CWI perception to cell wall biosynthesis and gene expression regulation. Furthermore, we address future perspectives and unanswered questions in the field, such as the identification of specific CWI sensing mechanisms and the role of CWI maintenance in the growth-defense trade-off. Elucidating these connections could have significant implications for crop improvement and sustainable agriculture.
... Nitric oxide (NO) is a gaseous biomolecule of the class of reactive nitrogen species (RNS), and has emerged as an important signaling molecule involved in diverse biological processes in both plants and animals [14][15][16][17][18][19][20] . In plants, NO has been shown to play a role in developmental and physiological processes, including floral transition, reaction to hypoxia, as well as immune and defense responses 17,21-23 . ...
... Nitric oxide (NO) is a gaseous biomolecule of the class of reactive nitrogen species (RNS), and has emerged as an important signaling molecule involved in diverse biological processes in both plants and animals [14][15][16][17][18][19][20] . In plants, NO has been shown to play a role in developmental and physiological processes, including floral transition, reaction to hypoxia, as well as immune and defense responses 17,[21][22][23] . ...
... Additionally, several lines of evidence have suggested that redox state plays an important role in stem cell homeostasis, including the key redox component RNS and reactive oxygen species (ROS) 15,19,[24][25][26] . NO and ROS are involved in controlling differentiation of embryonic stem cells in animals 15,27,28 and more recently, they have been shown to act as important signals in root and shoot stem cell systems of plants 16,19,20,24,25 . ...
Despite the importance of Nitric Oxide (NO) as signaling molecule in both plant and animal development, the regulatory mechanisms downstream of NO remain largely unclear. Here, we show that NO is involved in Arabidopsis shoot stem cell control via modifying expression and activity of ARGONAUTE 4 (AGO4), a core component of the RNA-directed DNA Methylation (RdDM) pathway. Mutations in components of the RdDM pathway cause meristematic defects, and reduce responses of the stem cell system to NO signaling. Importantly, we find that the stem cell inducing WUSCHEL transcription factor directly interacts with AGO4 in a NO dependent manner, explaining how these two signaling systems may converge to modify DNA methylation patterns. Taken together, our results reveal that NO signaling plays an important role in controlling plant stem cell homeostasis via the regulation of de novo DNA methylation.
... In relation to QC activity, the level of NO is influenced by PHB3; phb3 plants are defective in ABA-induced NO accumulation (Wang et al. 2010). High levels of NO reduce the number of meristematic cells by decreasing PIN-mediated auxin transport, as well as auxin activity and auxin sensitivity at the root pole (Sanz et al. 2014;Fernández-Marcos et al. 2011). These findings agree with similar phenotypic deviations, including the loss of QC definition, observed under conditions raising NO (Mira et al. 2023a). ...
Main conclusion
The preservation of quiescent center stem cell integrity in hypoxic roots by phytoglobins is exercised through their ability to scavenge nitric oxide and attenuate its effects on auxin transport and cell degradation. Under low oxygen stress, the retention or induction of phytoglobin expression maintains cell viability while loss or lack of induction of phytoglobin leads to cell degradation.
Abstract
Plants have evolved unique attributes to ensure survival in the environment in which they must exist. Common among the attributes is the ability to maintain stem cells in a quiescent (or low proliferation) state in unfriendly environments. From the seed embryo to meristematic regions of the plant, quiescent stem cells exist to regenerate the organism when environmental conditions are suitable to allow plant survival. Frequently, plants dispose of mature cells or organs in the process of acclimating to the stresses to ensure survival of meristems, the stem cells of which are capable of regenerating cells and organs that have been sacrificed, a feature not generally available to mammals. Most of the research on plant stress responses has dealt with how mature cells respond because of the difficulty of specifically examining plant meristem responses to stress. This raises the question as to whether quiescent stem cells behave in a similar fashion to mature cells in their response to stress and what factors within these critical cells determine whether they survive or degrade when exposed to environmental stress. This review attempts to examine this question with respect to the quiescent center (QC) stem cells of the root apical meristem. Emphasis is put on how varying levels of nitric oxide, influenced by the expression of phytoglobins, affect QC response to hypoxic stress.
... Environmental, genetic, or pharmacological perturbations of PIN localization patterns redistribute auxin within the root and can disrupt the expression of WOX5 and consequently the functionality of the RAM leading to growth inhibition (Friml et al. 2003;Liu et al. 2015;Mira et al. 2017). Nitric oxide (NO) is a factor modulating auxin response (Pagnussat et al. 2002) and transport (Fernández-Marcos et al. 2011) in root cells. Localization of PINs is altered by NO (Fernández-Marcos et al. 2011), as documented also in gravitropic responses (Paris et al. 2018;Cseplo et al. 2021), nutrient responses (Manoli et al. 2015;Lin et al. 2016;Liu et al. 2018), cadmium toxicity (Yuan and Huang 2016), and in vitro embryogenesis (Elhiti et al. 2013). ...
... Nitric oxide (NO) is a factor modulating auxin response (Pagnussat et al. 2002) and transport (Fernández-Marcos et al. 2011) in root cells. Localization of PINs is altered by NO (Fernández-Marcos et al. 2011), as documented also in gravitropic responses (Paris et al. 2018;Cseplo et al. 2021), nutrient responses (Manoli et al. 2015;Lin et al. 2016;Liu et al. 2018), cadmium toxicity (Yuan and Huang 2016), and in vitro embryogenesis (Elhiti et al. 2013). Accumulation of NO at the root tip through pharmacological applications (Fernández-Marcos et al. 2011), or following conditions of stress (Mira et al. , 2017(Mira et al. , 2020 consumes the QC and in some cases promotes deterioration of the meristematic cells culminating in root growth inhibition. ...
... Localization of PINs is altered by NO (Fernández-Marcos et al. 2011), as documented also in gravitropic responses (Paris et al. 2018;Cseplo et al. 2021), nutrient responses (Manoli et al. 2015;Lin et al. 2016;Liu et al. 2018), cadmium toxicity (Yuan and Huang 2016), and in vitro embryogenesis (Elhiti et al. 2013). Accumulation of NO at the root tip through pharmacological applications (Fernández-Marcos et al. 2011), or following conditions of stress (Mira et al. , 2017(Mira et al. , 2020 consumes the QC and in some cases promotes deterioration of the meristematic cells culminating in root growth inhibition. ...
Over-expression of phytoglobin mitigates the degradation of the root apical meristem (RAM) caused by waterlogging through changes in nitric oxide and auxin distribution at the root tip.
Plant performance to waterlogging is ameliorated by the over-expression of the Arabidopsis Phytoglobin 1 (Pgb1) which also contributes to the maintenance of a functional RAM. Hypoxia induces accumulation of ROS and damage in roots of wild type plants; these events were preceded by the exhaustion of the RAM resulting from the loss of functionality of the WOX5-expressing quiescent cells (QCs). These phenotypic deviations were exacerbated by suppression of Pgb1 and attenuated when the same gene was up-regulated. Genetic and pharmacological studies demonstrated that degradation of the RAM in hypoxic roots is attributed to a reduction in the auxin maximum at the root tip, necessary for the specification of the QC. This reduction was primarily caused by alterations in PIN-mediated auxin flow but not auxin synthesis. The expression and localization patterns of several PINs, including PIN1, 2, 3 and 4, facilitating the basipetal translocation of auxin and its distribution at the root tip, were altered in hypoxic WT and Pgb1-suppressing roots but mostly unchanged in those over-expressing Pgb1. Disruption of PIN1 and PIN2 signal in hypoxic roots suppressing Pgb1 initiated in the transition zone at 12 h and was specifically associated to the absence of Pgb1 protein in the same region. Exogenous auxin restored a functional RAM, while inhibition of the directional auxin flow exacerbated the degradation of the RAM. The regulation of root behavior by Pgb1 was mediated by nitric oxide (NO) in a model consistent with the recognized function of Pgbs as NO scavengers. Collectively, this study contributes to our understanding of the role of Pgbs in preserving root meristem function and QC niche during conditions of stress, and suggests that the root transition zone is most vulnerable to hypoxia.
... In Arabidopsis, the NIA1 and NIA2 genes encode nitrate reductases, which play redundant functions in nitrate to nitrite reduction (Li et al. 2007a, b;Park et al. 2011). This conversion releases nitric oxide (NO), a diffusible, reactive gas that acts as a reactive nitrogen species and as a cellular messenger important for the regulation of root growth and branching (Méndez-Bravo et al. 2010;Fernandez-Marcos et al. 2011;Dolch et al. 2017;Oláh et al. 2020). Although nitrate sensing, transport, and reduction are critical for plant productivity, the impact of root-associated bacteria in these processes has been scarcely investigated. ...
... Nitric oxide (NO) mediates both primary root growth and lateral root development and its cellular levels rise during nitrate reduction (Méndez-Bravo et al. 2010;Fernandez-Marcos et al. 2011). The increase of NO in roots as a possible response to P. aeruginosa PAO1 and ΔlasI was tested in Arabidopsis WT and nia1nia2 mutants using the fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2DA) and confocal microscopy 5 days after root interaction with bacterial streaks. ...
Main conclusion
In P. aeruginosa, mutation of the gene encoding N-acyl-L-homoserine lactone synthase LasI drives defense and plant growth promotion, and this latter trait requires adequate nitrate nutrition.
Abstract
Cross-kingdom communication with bacteria is crucial for plant growth and productivity. Here, we show a strong induction of genes for nitrate uptake and assimilation in Arabidopsis seedlings co-cultivated with P. aeruginosa WT (PAO1) or ΔlasI mutants defective on the synthesis of the quorum-sensing signaling molecule N-(3-oxododecanoyl)-L-homoserine lactone. Along with differential induction of defense-related genes, the change from plant growth repression to growth promotion upon bacterial QS disruption, correlated with upregulation of the dual-affinity nitrate transceptor CHL1/AtNRT1/NPF6.3 and the nitrate reductases NIA1 and NIA2. CHL1-GUS was induced in Arabidopsis primary root tips after transfer onto P. aeruginosa ΔlasI streaks at low and high N availability, whereas this bacterium required high concentrations of nitrogen to potentiate root and shoot biomass production and to improve root branching. Arabidopsis chl1-5 and chl1-12 mutants and double mutants in NIA1 and NIA2 nitrate reductases showed compromised growth under low nitrogen availability and failed to mount an effective growth promotion and root branching response even at high NH4NO3. WT P. aeruginosa PAO1 and P. aeruginosa ΔlasI mutant promoted the accumulation of nitric oxide (NO) in roots of both the WT and nia1nia2 double mutants, whereas NO donors SNP or SNAP did not improve growth or root branching in nia1nia2 double mutants with or without bacterial cocultivation. Thus, inoculation of Arabidopsis roots with P. aeruginosa drives gene expression for improved nitrogen acquisition and this macronutrient is critical for the plant growth-promoting effects upon disruption of the LasI quorum-sensing system.
... Secondly, when O 2 concentrations decrease, root growth rates of Arabidopsis also decrease, indicating that hypoxia also alters root extension rates (Huang et al., 1997;van Dongen et al., 2009). Thirdly, NO also reduced primary root growth (Fernández-Marcos et al., 2011). The concentration of NO is regulated by both ethylene and hypoxia (Sanchez-Corrionero et al., 2023) and for more information about NO as a root growth regulator, we refer the reader to Sanchez-Corrionero et al. (2023). ...
Plant submergence is a major abiotic stress that impairs plant performance. Underwater, reduced gas diffusion exposes submerged plant cells to an environment that is enriched in gaseous ethylene and is limited in oxygen (O2) availability (hypoxia). The capacity for plant roots to avoid and/or sustain critical hypoxia damage is essential for plants to survive waterlogging. Plants use spatiotemporal ethylene and O2 dynamics as instrumental flooding signals to modulate potential adaptive root growth and hypoxia stress acclimation responses. However, how non-adapted plant species modulate root growth behaviour during actual waterlogged conditions to overcome flooding stress has hardly been investigated. Here we discuss how changes in the root growth rate, lateral root formation, density and growth angle of non-flood adapted plant species (mainly Arabidopsis) could contribute to avoiding and enduring critical hypoxic conditions. In addition, we discuss the current molecular understanding of how ethylene and hypoxia signalling control these adaptive root growth responses. We propose that future research would benefit from less artificial experimental designs to better understand how plant roots respond to and survive waterlogging. This acquired knowledge would be instrumental to guide targeted breeding of flood-tolerant crops with more resilient root systems.
... It seems that, in plants, nitrate reductase (NR) plays the main role in the enzymatic NO production [19,20]. There are mutants impaired in NO production, including the Arabidopsis nia1nia2 mutants, altered in the NIA1 and NIA2 genes, encoding NRs [19,34], and mutants that overproduce NO, such as the Arabidopsis cue/nox1 mutants [19,35,36]. NO is usually detected and determined by using the permeable NO-sensitive fluorophore 4-amino-5-methylamino-2 ,7 -difluoro-fluorescein diacetate (DAF-FM DA) [13,34]. ...
... NO can affect GSH synthesis, and both NO and ethylene can affect auxin accumulation, distribution and signaling. Based on [8,9,11,[13][14][15][16]35,38,40,[53][54][55][56][57]. Nsy: Nitrosylation (ˆor →: promotion; Int. ...
Iron (Fe) is abundant in soils but with a poor availability for plants, especially in calcareous soils. To favor its acquisition, plants develop morphological and physiological responses, mainly in their roots, known as Fe deficiency responses. In dicot plants, the regulation of these responses is not totally known, but some hormones and signaling molecules, such as auxin, ethylene, glutathione (GSH), nitric oxide (NO) and S-nitrosoglutathione (GSNO), have been involved in their activation. Most of these substances, including auxin, ethylene, GSH and NO, increase their production in Fe-deficient roots while GSNO, derived from GSH and NO, decreases its content. This paradoxical result could be explained with the increased expression and activity in Fe-deficient roots of the GSNO reductase (GSNOR) enzyme, which decomposes GSNO to oxidized glutathione (GSSG) and NH3. The fact that NO content increases while GSNO decreases in Fe-deficient roots suggests that NO and GSNO do not play the same role in the regulation of Fe deficiency responses. This review is an update of the results supporting a role for NO, GSNO and GSNOR in the regulation of Fe deficiency responses. The possible roles of NO and GSNO are discussed by taking into account their mode of action through post-translational modifications, such as S-nitrosylation, and through their interactions with the hormones auxin and ethylene, directly related to the activation of morphological and physiological responses to Fe deficiency in dicot plants.
... Propidium iodide (PI) staining was performed as previously described (Fernandez-Marcos et al. 2011), and the root tips were observed using a Leica STELLARIS 5 confocal laser scanning microscope (Leica Microsystems CMS GmbH, Germany). ...
Background and aims
Phosphate (Pi) is an essential nutrient for plant growth and development. Accessible Pi is usually limited in soil and Pi starvation is a global stress for crops. Genetic approach is promising for sustainable agriculture to improve plant growth under Pi starvation. The aim of this study is to explore the role of transcription factor NUTCRACKER (NUC) in response to Pi starvation.
Methods
The seedlings growth, biomass, chlorophyll and anthocyanin contents, root morphology, phosphate starvation-induced (PSI) genes expression in NUC knockout, rescue and overexpression Arabidopsis lines were examined and compared under Pi sufficiency (CON) and Pi starvation conditions.
Results
Arabidopsis lines overexpressing NUC significantly improved their growth under Pi starvation by attenuating Pi starvation-induced harmful effects. NUC expression was significantly upregulated in roots and positively affected root development under Pi starvation. Specifically, overexpression of NUC elongated primary roots under Pi starvation by increasing meristem size and elongation zone, promoted the growth of Pi-starvation-induced root hairs, and increased the expression of phosphate starvation-induced genes in roots.
Conclusion
Overexpression of NUC conferred plants by tolerate to Pi starvation, and the promotion to root hair could be the main reason. NUC has the potential to improve plant growth under Pi starvation.
... Nitric oxide (NO) plays a versatile role in plant growth and development, including the roots [33]. For example, the NO signal, leading to decreased cell division and promoted cell differentiation in root meristems, is accumulated by abiotic stimuli, such as salt stress [34]. In addition, applying a NO biosynthetic inhibitor alleviates the salt-mediated growth inhibition of root meristems [35]. ...
... In addition, applying a NO biosynthetic inhibitor alleviates the salt-mediated growth inhibition of root meristems [35]. Moreover, the highly accumulated NO levels, which were observed in chlorophyll a/b binding protein underexpressed1/NO overproducer1 (cue1/nox1) mutants, are related to the reduced acropetal auxin transport and maxima via a decrease in the protein levels of the efflux carrier PIN-FORMED1 (PIN1), which leads to the disorganization of QC and columella stem cell (CSC) [34,35]. In this process, the low activity of auxin signaling caused by NO accumulation was enhanced by the stabilization of the auxin signaling repressor IAA17 [35]. ...
Salt stress severely affects plant growth and development. The plant growth and development of a sessile organism are continuously regulated and reformed in response to surrounding environmental stress stimuli, including salinity. In plants, postembryonic development is derived mainly from primary apical meristems of shoots and roots. Therefore, to understand plant tolerance and adaptation under salt stress conditions, it is essential to determine the stress response mechanisms related to growth and development based on the primary apical meristems. This paper reports that the biological roles of microRNAs, redox status, reactive oxygen species (ROS), nitric oxide (NO), and phytohormones, such as auxin and cytokinin, are important for salt tolerance, and are associated with growth and development in apical meristems. Moreover, the mutual relationship between the salt stress response and signaling associated with stem cell homeostasis in meristems is also considered.
... NO and auxin have an intricate relationship during SIMR; NO has been proven to have a downstream effector as well as an upstream regulator role in auxin responses [24][25][26]. In one hand, exogenous NO causes root meristem defects due to reduced PIN1-mediated acropetal auxin transport [16]. On the other hand, depletion of NO perturbs auxin biosynthesis, transport, and signaling, resulting in small root meristems with abnormal cell divisions and stem cell niche organization [26]. ...
... The key role of NO as a gaseous signal molecule was demonstrated to modulate hormonal crosstalk during various developmental or stress-induced alterations of RSA (for reviews [13][14][15]). NO treatment can evoke morphogenic responses in roots reducing the length of the PR [16], but enhancing lateral [17] or adventitious [18] root formation ...
... It has been reported that GSNO decreases the auxin maximum in the PR apex [16]. To investigate whether GSNO affects auxin transport in a ROP2-dependent way, localization of the PIN1 protein was examined via immunofluorescence in the apex of wild-type and rop2-1 roots exposed to GSNO ( Figure 5). ...
Nitric oxide (NO) is a versatile signal molecule that mediates environmental and hormonal signals orchestrating plant development. NO may act via reversible S-nitrosation of proteins during which an NO moiety is added to a cysteine thiol to form an S-nitrosothiol. In plants, several proteins implicated in hormonal signaling have been reported to undergo S-nitrosation. Here, we report that the Arabidopsis ROP2 GTPase is a further potential target of NO-mediated regulation. The ROP2 GTPase was found to be required for the root shortening effect of NO. NO inhibits primary root growth by altering the abundance and distribution of the PIN1 auxin efflux carrier protein and lowering the accumulation of auxin in the root meristem. In rop2-1 insertion mutants, however, wild-type-like root size of the NO-treated roots were maintained in agreement with wild-type-like PIN1 abundance in the meristem. The ROP2 GTPase was shown to be S-nitrosated in vitro, suggesting that NO might directly regulate the GTPase. The potential mechanisms of NO-mediated ROP2 GTPase regulation and ROP2-mediated NO signaling in the primary root meristem are discussed.
