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The phytohormone ethylene regulates multiple aspects of plant growth and development and responses to environmental stress. However, the exact role of ethylene in freezing stress remains unclear. Here, we report that ethylene negatively regulates plant responses to freezing stress in Arabidopsis thaliana. Freezing tolerance was decreased in ethylen...
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... we examined whether these ARR-OE transgenic plants had altered expression of cold-regulated genes in the CBF pathway. No obvious differences were detected in the expression of CBF1-3 , RD29A , COR15b , and COR47 between ARR-OE plants and the wild type before or after cold treatment (see Supplemental Figure 10 online). These results suggest that ARR5 , ARR7 , and ARR15 are involved in freezing tolerance uncoupled with the CBF pathway. Because the overaccumulation of type-A ARR contributes to the freezing tolerance of ethylene-insensitive mutants (Figure 8) and the ACC-treated seedlings exhibited a hypersensitivity to freezing tolerance (Figure 1), we reasoned that the activation of ethylene biosynthesis should disturb the accumulation of type-A ARR proteins. To test this hypothesis, we fi rst analyzed the transcript levels of the ARR5 , ARR7 , and ARR15 genes in plants treated with ACC. Strikingly, the levels of ARR5 , ARR7 , and ARR15 expression were drastically reduced after ACC treatment (Figure 9A). Next, we examined the effect of ACC on the GUS activity in the transgenic plants expressing ARR5 : GUS under cold stress and BA treatment. In agreement with previous studies (D ’ Agostino et al., 2000; Fowler and Thomashow, 2002), ARR5 was induced by cold stress and BA treatment. However, the induction of ARR5 by cold and BA was signi fi cantly blocked by exogenous ACC (see Supplemental Figure 11 online), further indicating the negative regulation of ARR5 expression by ethylene. Next, we found that the decrease in the ARR5, ARR7, and ARR15 protein levels in response to ACC treatment was similar to the pattern of expression of the corresponding genes (Figure 9B). The type-A ARR proteins could be stabilized by MG132, a speci fi c proteasomal inhibitor, which is consistent with the results from a previous report (Ren et al., 2009). Furthermore, the ACC-induced reduction of the ARR5, ARR7, and ARR15 protein levels was also inhibited by MG132 (Figure 9B), indicating that ACC-induced type-A ARR degradation is dependent on the proteasome ...
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... the ARR-Myc immunoblots, 2-week-old ARR-OE transgenic seedlings (Ren et al., 2009) were treated with 10 m M ACC at 4°C or treated with ACC plus MG132 for the indicated period of time. The ARR-Myc fusion proteins were visualized on immunoblots using an anti-Myc antibody (Sigma-Aldrich). For the EIN3-GFP immunoblots, 7-d-old 35S : EIN3-GFP transgenic plants were treated at 4°C for the indicated period of time, or they were treated with ACC or MG132 for 6 h. The EIN3-GFP fusion proteins were visualized on immunoblots using an anti-GFP antibody (Sigma-Aldrich). For the EBF1-GFP and EBF1-Myc immunoblots, 7-d-old 35S : EIN3- GFP and 35S : EBF1-TAP ein2 plants were treated at 4°C for the indicated period of time. The EIN3-GFP and EBF1-Myc fusion proteins were visualized on immunoblots using an anti-GFP or anti-Myc antibody (Sigma- Aldrich). As controls, HSP90 protein was visualized on immunoblots using an anti-HSP90 antibody (Sigma-Aldrich), and ribulose-1,5-bisphosphate carboxylase/oxygenase protein was stained by Ponceau S. The fl uorescence of GFP in the roots of 7-d-old transgenic plants expressing 35S : EIN3-GFP or 35S : EBF1-GFP was imaged using a confocal laser scanning microscope (LSM510; Carl Zeiss) at 0, 3, 6, and 12 h of cold treatment or at 6 h of ACC treatment. Sequence data from this article can be found in the Arabidopsis Genome Initiative or GenBank/EMBL databases under the following accession num- bers: ETR1 (At1g66340), EIN4 (At3g04580), CTR1 (At5g03730), EIN2 (At5g03280), EIN3 (At3g20770), EIL1 (At2g27050), ETO1 (At3g51770), EBF1 (At2g25490), EBF2 (At5g25350), CBF1 (At4g25490), CBF2 (At4g25470), CBF3 (At4g25480), RD29A (At5g52310), COR15B (At2g42530), KIN1 (At5g15960), COR414 (At1g29395), COR47 (At1g20440), ARR5 (At3g48100), ARR7 (At1g19050), ARR15 (At1g74890), ACTIN2/8 (At3g18780/At1g49240), and TUBULIN2 (At5g62690). The following materials are available in the online version of this article. Supplemental Figure 1. Freezing Tolerance Assay of Mutants in the Ethylene Signaling Pathway after Cold Acclimation. Figure 2. Freezing Tolerance of Col Plants Is Not Affected by -Estradiol Application. Levels of EIN3 and EBF1 Proteins after Cold Stress. GUS Activity of : in Trans- genic Plants. Schematic Diagrams Showing the Promoter Structures of the , ARR5 , ARR7 , and ARR15 Genes. EMSA Assays for EIN3 Binding to the Promoters of , , ARR7 , and . Immunoblot Analysis of the ARR5, ARR7, and ARR15 Proteins in -Overexpressing Plants. The Effect of BA on the Freezing Tolerance of Wild-Type Plants. 9. The Effect of -Zeatin on the Freezing Tolerance of Plants. Figure 10. Expression of Cold-Regulated Genes in Plants under Cold ...
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... family of receptors (ETHYLENE RESPONSE1 [ETR1], ETR2, ETHYLENE RESPONSE SENSOR1 [ERS1], ERS2, and ETHYLENE INSENSITIVE4 [EIN4]) that act negatively and redundantly in ethylene signaling (Chang et al., 1993; Hua et al., 1995, 1998; Sakai et al., 1998). In the absence of ethylene, ethylene receptors interact with CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), a Raf-like Ser/Thr protein kinase, and positively regulate its activity (Kieber et al., 1993; Gao et al., 2003). The negative regulator CTR1 in turn directly or indirectly inhibits EIN2, which is an essential positive regulator of ethylene signaling (Alonso et al., 1999). The EIN3/EIN3-Like1 (EIL1) transcription factors function downstream of EIN2 in ethylene signaling (Chao et al., 1997; Solano et al., 1998). It has been shown that ethylene- induced EIN3/EIL1 stability is mediated by the proteasomal degradation of two F-box proteins, EIN3 Binding F-box1 (EBF1) and EBF2 (Guo and Ecker, 2003; Potuschak et al., 2003; An et al., 2010). EIN3/EIL1 activate or repress the expression of ethylene response target genes by speci fi cally binding to their promoters, thereby modulating the ethylene-related responses of plants (Alonso et al., 2003; Chen et al., 2009; Zhong et al., 2009; Boutrot et al., 2010; Zhang et al., 2011). Although ethylene has been implicated in the cold stress response (Harber and Fuchigami, 1989; Ciardi et al., 1997; Yu et al., 2001; Zhang and Huang, 2010), the exact role that ethylene plays in the regulation of freezing stress remains unclear. Here, we un- dertook a molecular and genetic approach to investigate the role of ethylene biosynthesis and signaling in plant response to freezing stress. We showed that increased ethylene levels led to decreased tolerance of freezing, whereas blocking ethylene biosynthesis and ethylene signaling enhanced freezing tolerance. Moreover, a set of ethylene-insensitive mutants, including etr1-1 , ein4-1 , ein2-5 , and ein3 eil1 , displayed enhanced tolerance to freezing, whereas the ctr1-1 mutant and EIN3 -overexpressing plants were greatly impaired in their responses to freezing stress. We further showed that the EIN3 protein was capable of directly binding to the promoters of the CBF1-CBF3 and type-A ARR5 , ARR7 , and ARR15 genes to repress their expression. Consistent with this, the overexpression of these ARR genes promoted freezing tolerance. These results indicate that ethylene biosynthesis and signaling negatively regulate plant freezing tolerance by repressing the cold-inducible CBFs and type-A ARR genes in Arabidopsis . Ethylene is thought to regulate the responses of plants to various abiotic stresses, including salt, drought, and cold stresses (Zhao and Schaller, 2004; Achard et al., 2006; Cao et al., 2007; Wang et al., 2007). To explore the exact role of ethylene in cold stress in Arabidopsis , we fi rst tested whether the freezing tolerance of wild-type plants was affected by altered ethylene biosynthesis under nonacclimated and cold-acclimated (7 d at 4°C) conditions. With or without cold acclimation, the wild- type plants treated with the ethylene biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (ACC) displayed decreased tolerance to freezing (Figure 1A). In the absence of cold acclimation, ; 50% of the wild-type Columbia (Col) plants were still alive, whereas only 31% of the ACC-treated plants survived after exposure to a temperature of 2 4°C (Figure 1C). Consistent with this, the ethylene overproduction mutant eto1 also showed reduced freezing tolerance compared with the wild-type plants (Figures 1B and 1C). By contrast, application of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) dramatically enhanced the freezing tolerance of both wild-type and eto1 plants (Figures 1A and 1B). AVG-treated Col and eto1 plants exhibited signi fi cantly higher survival rates after exposure to 2 4°C (95 and 90% survival, respectively) compared with the untreated Col and eto1 plants (50 and 36% survival, respectively) (Figure 1C). The relative electrolyte leakage serves as an indicator of cell membrane integrity damage caused by cold stress (Lyons, 1973); therefore, we measured changes in the electrolyte leakage of wild-type Col, eto1 , and ACC- and AVG- treated plants. The eto1 and ACC-treated Col plants had higher electrolyte leakage, whereas the AVG-treated Col and eto1 plants had lower electrolyte leakage than the wild-type Col plants in response to freezing temperatures of 2 4, 2 5, and 2 6°C (Figure 1D). Taken together, these results indicate that ethylene has a negative effect on freezing tolerance in Arabidopsis . We next examined whether ethylene signaling is involved in plant responses to freezing stress. In the presence of the ethylene receptor antagonist Ag + , the survival rates of both wild- type Col and eto1 plants were signi fi cantly increased when the plants were exposed to freezing stress in the absence of cold acclimation (Figures 1B and 1C), and the levels of electrolyte leakage in both the Ag + -treated Col and eto1 plants were much lower than in untreated Col and eto1 (Figure 1D). This result indicates that the blockage of ethylene signaling improves the tolerance of plants to freezing temperatures. To determine the role that ethylene signaling plays during cold stress further, we tested the freezing tolerance of a set of mutants in the ethylene signaling pathway: etr1-1 , ein4-1 , ctr1-1 , ein2-5 , ein3-1 , eil1-1 , and ein3 eil1 . etr1-1 and ein4-1 mutants are the gain-of-function ethylene receptor mutants; they exhibited a substantially increased tolerance to freezing under nonacclimated and acclimated conditions (Figures 2A and 2B; see Supplemental Figure 1 online). EIN2 and EIN3 are key positive regulators in the ethylene signaling. The loss-of-function mutant ein2-5 was more tolerant to freezing stress than the wild-type plants. The survival rate of the loss-of-function mutant ein3-1 was slightly higher than that of the wild-type plants, and the eil1-1 mutant behaved similarly to the wild-type plants after freezing treatment. The ein3 eil1 double mutant displayed a constitutively enhanced freezing tolerance (Figures 2A and 2B; see Supplemental Figure 1 online). Electrolyte leakage was dramatically less in etr1-1 , ein4-1 , ein2-5 , and ein3 eil1 double mutant than in the wild-type plants following the freezing treatment, and the ein3-1 and eil1-1 plants exhibited slightly lower electrolyte leakage than ...
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... family of receptors (ETHYLENE RESPONSE1 [ETR1], ETR2, ETHYLENE RESPONSE SENSOR1 [ERS1], ERS2, and ETHYLENE INSENSITIVE4 [EIN4]) that act negatively and redundantly in ethylene signaling (Chang et al., 1993; Hua et al., 1995, 1998; Sakai et al., 1998). In the absence of ethylene, ethylene receptors interact with CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), a Raf-like Ser/Thr protein kinase, and positively regulate its activity (Kieber et al., 1993; Gao et al., 2003). The negative regulator CTR1 in turn directly or indirectly inhibits EIN2, which is an essential positive regulator of ethylene signaling (Alonso et al., 1999). The EIN3/EIN3-Like1 (EIL1) transcription factors function downstream of EIN2 in ethylene signaling (Chao et al., 1997; Solano et al., 1998). It has been shown that ethylene- induced EIN3/EIL1 stability is mediated by the proteasomal degradation of two F-box proteins, EIN3 Binding F-box1 (EBF1) and EBF2 (Guo and Ecker, 2003; Potuschak et al., 2003; An et al., 2010). EIN3/EIL1 activate or repress the expression of ethylene response target genes by speci fi cally binding to their promoters, thereby modulating the ethylene-related responses of plants (Alonso et al., 2003; Chen et al., 2009; Zhong et al., 2009; Boutrot et al., 2010; Zhang et al., 2011). Although ethylene has been implicated in the cold stress response (Harber and Fuchigami, 1989; Ciardi et al., 1997; Yu et al., 2001; Zhang and Huang, 2010), the exact role that ethylene plays in the regulation of freezing stress remains unclear. Here, we un- dertook a molecular and genetic approach to investigate the role of ethylene biosynthesis and signaling in plant response to freezing stress. We showed that increased ethylene levels led to decreased tolerance of freezing, whereas blocking ethylene biosynthesis and ethylene signaling enhanced freezing tolerance. Moreover, a set of ethylene-insensitive mutants, including etr1-1 , ein4-1 , ein2-5 , and ein3 eil1 , displayed enhanced tolerance to freezing, whereas the ctr1-1 mutant and EIN3 -overexpressing plants were greatly impaired in their responses to freezing stress. We further showed that the EIN3 protein was capable of directly binding to the promoters of the CBF1-CBF3 and type-A ARR5 , ARR7 , and ARR15 genes to repress their expression. Consistent with this, the overexpression of these ARR genes promoted freezing tolerance. These results indicate that ethylene biosynthesis and signaling negatively regulate plant freezing tolerance by repressing the cold-inducible CBFs and type-A ARR genes in Arabidopsis . Ethylene is thought to regulate the responses of plants to various abiotic stresses, including salt, drought, and cold stresses (Zhao and Schaller, 2004; Achard et al., 2006; Cao et al., 2007; Wang et al., 2007). To explore the exact role of ethylene in cold stress in Arabidopsis , we fi rst tested whether the freezing tolerance of wild-type plants was affected by altered ethylene biosynthesis under nonacclimated and cold-acclimated (7 d at 4°C) conditions. With or without cold acclimation, the wild- type plants treated with the ethylene biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (ACC) displayed decreased tolerance to freezing (Figure 1A). In the absence of cold acclimation, ; 50% of the wild-type Columbia (Col) plants were still alive, whereas only 31% of the ACC-treated plants survived after exposure to a temperature of 2 4°C (Figure 1C). Consistent with this, the ethylene overproduction mutant eto1 also showed reduced freezing tolerance compared with the wild-type plants (Figures 1B and 1C). By contrast, application of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) dramatically enhanced the freezing tolerance of both wild-type and eto1 plants (Figures 1A and 1B). AVG-treated Col and eto1 plants exhibited signi fi cantly higher survival rates after exposure to 2 4°C (95 and 90% survival, respectively) compared with the untreated Col and eto1 plants (50 and 36% survival, respectively) (Figure 1C). The relative electrolyte leakage serves as an indicator of cell membrane integrity damage caused by cold stress (Lyons, 1973); therefore, we measured changes in the electrolyte leakage of wild-type Col, eto1 , and ACC- and AVG- treated plants. The eto1 and ACC-treated Col plants had higher electrolyte leakage, whereas the AVG-treated Col and eto1 plants had lower electrolyte leakage than the wild-type Col plants in response to freezing temperatures of 2 4, 2 5, and 2 6°C (Figure 1D). Taken together, these results indicate that ethylene has a negative effect on freezing tolerance in Arabidopsis . We next examined whether ethylene signaling is involved in plant responses to freezing stress. In the presence of the ethylene receptor antagonist Ag + , the survival rates of both wild- type Col and eto1 plants were signi fi cantly increased when the plants were exposed to freezing stress in the absence of cold acclimation (Figures 1B and 1C), and the levels of electrolyte leakage in both the Ag + -treated Col and eto1 plants were much lower than in untreated Col and eto1 (Figure 1D). This result indicates that the blockage of ethylene signaling improves the tolerance of plants to freezing temperatures. To determine the role that ethylene signaling plays during cold stress further, we tested the freezing tolerance of a set of mutants in the ethylene signaling pathway: etr1-1 , ein4-1 , ctr1-1 , ein2-5 , ein3-1 , eil1-1 , and ein3 eil1 . etr1-1 and ein4-1 mutants are the gain-of-function ethylene receptor mutants; they exhibited a substantially increased tolerance to freezing under nonacclimated and acclimated conditions (Figures 2A and 2B; see Supplemental Figure 1 online). EIN2 and EIN3 are key positive regulators in the ethylene signaling. The loss-of-function mutant ein2-5 was more tolerant to freezing stress than the wild-type plants. The survival rate of the loss-of-function mutant ein3-1 was slightly higher than that of the wild-type plants, and the eil1-1 mutant behaved similarly to the wild-type plants after freezing treatment. The ein3 eil1 double mutant displayed a constitutively enhanced freezing tolerance (Figures 2A and 2B; see Supplemental Figure 1 online). Electrolyte leakage was dramatically less in etr1-1 , ein4-1 , ein2-5 , and ein3 eil1 double mutant than in the wild-type plants following the freezing treatment, and the ein3-1 and eil1-1 plants exhibited slightly lower electrolyte leakage than ...
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... After the freezing treatment (specific time and temperature details provided in the figure legends), the seedlings were kept at 4 ℃ for 12 h and then recovered for 72 h at 4 ℃. Subsequently, the survival rates [51], ion leakage [52], POD [53], SOD [54], and CAT activities and MDA content [55] were determined. For soil-grown seedlings, 28-day-old seedlings were subjected to the freezing assay treatment as described in the figure legends (specific time and temperature details provided). ...
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The cytokinin signaling pathway is important for plant growth and development. To understand the regulatory process, a type A response regulator, SmRR5, in Salix matsudana Koidz., was characterized and functionally analyzed. Gene expression tests showed that SmRR5 was distinctly higher in the leaves and roots of the fast-growing S. matsudana variety 9901 than in those of the slow-growing variety Yanjing (YJ). The transcript abundance was highest in the meristem zone (MEZ), followed by the elongation zone (EZ) and maturation zone (MAZ) in 9901 roots, but it was identically low in YJ roots. Overexpression of SmRR5 in tobacco plants significantly improved plant height, maximum root length (MRL), lateral root number (LRN), fresh weight (FW), dry weight (DW), and flowering time compared with wild-type plants. Transcript profiling revealed that multiple genes associated with flowering (SWEET1, FPF1, and COL12), plant growth (YUCCA8, PIN5, and ARF9a), and adventitious root (AR) formation (Hox3, MYC2, and AGL46) were highly expressed in the overexpression of leaves and roots. Thus, SmRR5 effectively facilitated plant growth and development.
... The endogenous ETHY levels in plants are impacted by abiotic stressors such low temperature and salinity. Higher ETHY concentrations were subsequently seen with improved tolerance Lal et al., 2022c;Shi et al., 2012). ETHY also plays a crucial role in the way plants defend themselves against heat stress (Song et al., 2014). ...
Environmental challenges, both biotic and abiotic, have a detrimental impact on plant growth and development, and plants must adopt particular strategies to sustain optimal growth under stress conditions. These strategies include molecular, biochemical, and physiological methods to deal with these demands. One of these mechanisms is the production of phytohormones. Organic substances known as phytohormones affect a number of physiological functions of plants, such as cell differentiation, growth, and development. Phytohormones govern physiological processes that are necessary to both normal and stressed situations. By facilitating a variety of adaptive responses, they play a significant part in enhancing plants’ capacity to adapt to challenging environmental conditions. Plants are able to adjust to shifting soil conditions because of these reactions. Plants use phytohormones for a wide range of purposes, both individually and collectively. The nature and concentration of these hormones have an impact on plant processes and functions. The most significant endogenous compounds that play a crucial role in regulating physiological reactions that finally result in stress adaptation are believed to be phytohormones. The current study discusses the potential contribution of phytohormones to stress-induced plant growth and development. It has been discussed where the main groups of plant hormones are produced. In addition to being necessary for plant growth and development, phytohormones are also essential for controlling how plants react to various abiotic stress situations. This chapter provides an overview of the methods used to treat salt stress in crops, including gibberellic acid (GA), brassinosteroids (BR), abscisic acid (ABA), indole acetic acid (IAA), cytokinins (CK), jasmonates (JA), salicylic acid (SA), and triazoles (TR).
