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1.
Environmental inputs such as stress can modulate plant cell metabolism, but the detailed mechanism remains unclear. We report here that FERONIA (FER), a plasma membrane receptor‐like kinase, may negatively regulate the S‐adenosylmethionine (SAM) synthesis by interacting with two S‐adenosylmethionine synthases (SAM1 and SAM2). SAM participates in ethylene, nicotianamine and polyamine biosynthetic pathways and provides the methyl group for protein and DNA methylation reactions. The Arabidopsis fer mutants contained a higher level of SAM and ethylene in plant tissues and displayed a dwarf phenotype. Such phenotype in the fer mutants was mimicked by over‐expressing the S‐adenosylmethionine synthetase in transgenic plants, whereas sam1/2 double mutant showed an opposite phenotype. We propose that FER receptor kinase, in response to environmental stress and plant hormones such as auxin and BR, interacts with SAM synthases and down‐regulates ethylene biosynthesis. 相似文献
5.
S‐adenosyl‐l ‐methionine (SAM) is the major methyl donor in cells and it is also used for the biosynthesis of polyamines and the plant hormone ethylene. During climacteric ripening of tomato ( Solanum lycopersicum ‘Bonaparte’), ethylene production rises considerably which makes it an ideal object to study SAM involvement. We examined in ripening fruit how a 1‐MCP treatment affects SAM usage by the three major SAM‐associated pathways. The 1‐MCP treatment inhibited autocatalytic ethylene production but did not affect SAM levels. We also observed that 1‐(malonylamino)cyclopropane‐1‐carboxylic acid formation during ripening is ethylene dependent. SAM decarboxylase expression was also found to be upregulated by ethylene. Nonetheless polyamine content was higher in 1‐MCP‐treated fruit. This leads to the conclusion that the ethylene and polyamine pathway can operate simultaneously. We also observed a higher methylation capacity in 1‐MCP‐treated fruit. During fruit ripening substantial methylation reactions occur which are gradually inhibited by the methylation product S‐adenosyl‐l ‐homocysteine (SAH). SAH accumulation is caused by a drop in adenosine kinase expression, which is not observed in 1‐MCP‐treated fruit. We can conclude that tomato fruit possesses the capability to simultaneously consume SAM during ripening to ensure a high rate of ethylene and polyamine production and transmethylation reactions. SAM usage during ripening requires a complex cellular regulation mechanism in order to control SAM levels. 相似文献
6.
Whether long interspersed nuclear element‐1 (LINE‐1) hypomethylation induced by reactive oxygen species (ROS) was mediated through the depletion of S‐adenosylmethionine (SAM) was investigated. Bladder cancer (UM‐UC‐3 and TCCSUP) and human kidney (HK‐2) cell lines were exposed to 20 μM H 2O 2 for 72 h to induce oxidative stress. Level of LINE‐1 methylation, SAM and homocysteine (Hcy) was measured in the H 2O 2‐exposed cells. Effects of α‐tocopheryl acetate (TA), N‐acetylcysteine (NAC), methionine, SAM and folic acid on oxidative stress and LINE‐1 methylation in the H 2O 2‐treated cells were explored. Viabilities of cells treated with H 2O 2 were not significantly changed. Intracellular ROS production and protein carbonyl content were significantly increased, but LINE‐1 methylation was significantly decreased in the H 2O 2‐treated cells. LINE‐1 methylation was restored by TA, NAC, methionine, SAM and folic acid. SAM level in H 2O 2‐treated cells was significantly decreased, while total glutathione was significantly increased. SAM level in H 2O 2‐treated cells was restored by NAC, methionine, SAM and folic acid; while, total glutathione level was normalized by TA and NAC. Hcy was significantly decreased in the H 2O 2‐treated cells and subsequently restored by NAC. In conclusion, in bladder cancer and normal kidney cells exposed to H 2O 2, SAM and Hcy were decreased, but total glutathione was increased. Treatments with antioxidants (TA and NAC) and one‐carbon metabolites (SAM, methionine and folic acid) restored these changes. This pioneer finding suggests that exposure of cells to ROS activates glutathione synthesis via the transsulfuration pathway leading to deficiency of Hcy, which consequently causes SAM depletion and eventual hypomethylation of LINE‐1. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
S-adenosylmethionine synthetase is a member of the stress-induced family genes. Our previous research indicated that overexpression of SlSAMS1 confers alkali stress tolerance to tomato seedlings. However, information regarding the alkali stress tolerance mechanism of SlSAMS1 and the cross-linked network between SlSAMS1 and downstream signal has been limited. To study how SlSAMS1 improves alkali stress tolerance, we manipulated the SlSAMS1 transgenic calluses through a pharmacological approach and found that overexpression of SlSAMS1 was positively correlated with polyamine (PA) and hydrogen peroxide (H2O2) accumulation leading to improve alkali stress tolerance. Additionally, the accumulation of H2O2 in SlSAMS1 overexpression calluses depended on polyamine oxidase activity. The activities of antioxidant system, accumulation of organic acid, Na+ detoxification as well as alkali stress tolerance of the SlSAMS1 transgenic calluses were reversed by PA biosynthesis inhibitors, but not significantly influenced by ethylene biosynthesis inhibitors. These results suggest that overexpression of SlSAMS1 enhances alkali stress tolerance through PA and H2O2 cross-linked networks, which provide new insight into how SlSAMS1 functions as a stress mediatory element in regulating plants tolerance to alkali stress. 相似文献
10.
Vibrio vulnificus contains two coproporphyrinogen III oxidases (CPOs): O 2‐dependent HemF and O 2‐independent HemN. The growth of the hemF mutant HF1 was similar to wild‐type cells at pH 7.5 under 2% O 2 conditions where HemN was active and had a half‐life of 64 min. However, HF1 did not grow when the medium pH decreased to pH 5.0, where oxidative stress affects endogenous S‐adenosylmethionine (SAM) levels. The growth of HF1 was restored not only by elevating the expression of MnSOD but also through the exogenous addition of SAM. For HF1 to grow under these SAM‐limiting conditions, a mutation arose in hemN, encoding HemN Y74F. Refolding of the denatured enzymes in vitro revealed that the apparent binding affinity of HemN Y74F for the cofactor SAM1, which coordinates the 4Fe‐4S cluster, was approximately sixfold higher than that of HemN. The Km of HemN Y74F for the co‐substrate SAM2, which provides radicals for CPO reactions, was threefold lower than that of HemN. Thus, affinities for both SAM1 and SAM2 were higher with the Y74F mutation. Taken together, when SAM is limiting, HemN is apparently nonfunctional, and heme synthesis is continued by HemF. 相似文献
13.
Heterotrimeric G proteins function as key players in hydrogen peroxide (H 2O 2) production in plant cells, but whether G proteins mediate ethylene‐induced H 2O 2 production and stomatal closure are not clear. Here, evidences are provided to show the Gα subunit GPA1 as a missing link between ethylene and H 2O 2 in guard cell ethylene signalling. In wild‐type leaves, ethylene‐triggered H 2O 2 synthesis and stomatal closure were dependent on activation of Gα. GPA1 mutants showed the defect of ethylene‐induced H 2O 2 production and stomatal closure, whereas wGα and cGα overexpression lines showed faster stomatal closure and H 2O 2 production in response to ethylene. Ethylene‐triggered H 2O 2 generation and stomatal closure were impaired in RAN1, ETR1, ERS1 and EIN4 mutants but not impaired in ETR2 and ERS2 mutants. Gα activator and H 2O 2 rescued the defect of RAN1 and EIN4 mutants or etr1‐3 in ethylene‐induced H 2O 2 production and stomatal closure, but only rescued the defect of ERS1 mutants or etr1‐1 and etr1‐9 in ethylene‐induced H 2O 2 production. Stomata of CTR1 mutants showed constitutive H 2O 2 production and stomatal closure, but which could be abolished by Gα inhibitor. Stomata of EIN2, EIN3 and ARR2 mutants did not close in responses to ethylene, Gα activator or H 2O 2, but do generate H 2O 2 following challenge of ethylene or Gα activator. The data indicate that Gα mediates ethylene‐induced stomatal closure via H 2O 2 production, and acts downstream of RAN1, ETR1, ERS1, EIN4 and CTR1 and upstream of EIN2, EIN3 and ARR2. The data also show that ETR1 and ERS1 mediate both ethylene and H 2O 2 signalling in guard cells. 相似文献
15.
Brassinosteroids (BRs) are essential for plant growth and development; however, whether and how they promote stomatal closure is not fully clear. In this study, we report that 24‐epibrassinolide (EBR), a bioactive BR, induces stomatal closure in Arabidopsis ( Arabidopsis thaliana) by triggering a signal transduction pathway including ethylene synthesis, the activation of Gα protein, and hydrogen peroxide (H 2O 2) and nitric oxide (NO) production. EBR initiated a marked rise in ethylene, H 2O 2 and NO levels, necessary for stomatal closure in the wild type. These effects were abolished in mutant bri1‐301, and EBR failed to close the stomata of gpa1 mutants. Next, we found that both ethylene and Gα mediate the inductive effects of EBR on H 2O 2 and NO production. EBR‐triggered H 2O 2 and NO accumulation were canceled in the etr1 and gpa1 mutants, but were strengthened in the eto1‐1 mutant and the cGα line (constitutively overexpressing the G protein α‐subunit AtGPA1). Exogenously applied H 2O 2 or sodium nitroprusside (SNP) rescued the defects of etr1‐3 and gpa1 or etr1 and gpa1 mutants in EBR‐induced stomatal closure, whereas the stomata of eto1‐1/ AtrbohF and cGα/ AtrbohF or eto1‐1/ nia1‐2 and cGα /nia1‐2 constructs had an analogous response to H 2O 2 or SNP as those of AtrbohF or Nia1‐2 mutants. Moreover, we provided evidence that Gα plays an important role in the responses of guard cells to ethylene. Gα activator CTX largely restored the lesion of the etr1‐3 mutant, but ethylene precursor ACC failed to rescue the defects of gpa1 mutants in EBR‐induced stomatal closure. Lastly, we demonstrated that Gα‐activated H 2O 2 production is required for NO synthesis. EBR failed to induce NO synthesis in mutant AtrbohF, but it led to H 2O 2 production in mutant Nia1‐2. Exogenously applied SNP rescued the defect of AtrbohF in EBR‐induced stomatal closure, but H 2O 2 did not reverse the lesion of EBR‐induced stomatal closure in Nia1‐2. Together, our results strongly suggest a signaling pathway in which EBR induces ethylene synthesis, thereby activating Gα, and then promotes AtrbohF‐dependent H 2O 2 production and subsequent Nia1‐catalyzed NO accumulation, and finally closes stomata. 相似文献
17.
The beneficial effects of melatonin on abiotic stress have been demonstrated in several plants. However, little is known about the signal transduction pathway of melatonin involved in the plant stress response. Here, we manipulated the melatonin levels in tomato plants through a chemical approach. The roles of melatonin in stress tolerance were studied by assessing the symptoms, chlorophyll fluorescence and stress‐responsive gene expression. Moreover, both chemical and genetic approaches were used to study the roles of hydrogen peroxide (H 2O 2) in melatonin‐induced signal transduction in tomato plants. We found that melatonin activates NADPH oxidase (RBOH) to enhance H 2O 2 levels by reducing its S‐nitrosylation activity. Furthermore, melatonin‐induced H 2O 2 accumulation was accompanied by obtainable stress tolerance. Inhibition of RBOH or chemical scavenging of H 2O 2 significantly reduced the melatonin‐induced defense response, including reduced expression of several stress‐related genes ( CDPK1, MAPK1, TSPMS, ERF4, HSP80 and ERD15) and reduced antioxidative enzyme activity (SOD, CAT and APX), which were responsible for the stress tolerance. Collectively, these results revealed a novel mechanism in which RBOH activity and H 2O 2 signaling are important components of the melatonin‐induced stress tolerance in tomato plants. 相似文献
18.
S‐adenosyl‐l ‐methionine (SAM) synthetase is the key enzyme involved in the biosynthesis of SAM, which serves as a common precursor for polyamines (PAs) and ethylene. A SAM synthetase cDNA ( SlSAMS1) was introduced into the tomato genome using the Agrobacterium tumefaciens transformation method. Transgenic plants overexpressing SlSAMS1 exhibited a significant increase in tolerance to alkali stress and maintained nutrient balance, higher photosynthetic capacity and lower oxidative stress compared with WT lines. Both in vivo and in vitro experiments indicated that the function of SlSAMS1 mainly depended on the accumulation of Spd and Spm in the transgenic lines. A grafting experiment showed that rootstocks from SlSAMS1‐overexpressing plants provided a stronger root system, increased PAs accumulation, essential elements absorption, and decreased Na + absorption in the scions under alkali stress. As a result, fruit set and yield were significantly enhanced. To our knowledge, this is the first report to provide evidence that SlSAMS1 positively regulates tomato tolerance to alkali stress and plays a major role in modulating polyamine metabolism, resulting in maintainability of nutrient and ROS balance. 相似文献
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