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S-adenosyl-L-methionine is an effector in the posttranscriptional autoregulation of the cystathionine gamma-synthase gene in Arabidopsis.

ABSTRACT: Cystathionine gamma-synthase, the first committed enzyme of methionine biosynthesis in higher plants, is encoded by the CGS1 gene in Arabidopsis thaliana. We have shown previously that the stability of the CGS1 mRNA is negatively regulated in response to methionine application [Chiba, Y., Ishikawa, M., Kijima, F., Tyson, R. H., Kim, J., Yamamoto, A., Nambara, E., Leustek, T., Wallsgrove, R. M. & Naito, S. (1999) Science 286, 1371-1374]. To determine whether methionine itself is the effector of the CGS1 exon 1-mediated posttranscriptional regulation, we carried out transfection experiments. The results suggested that, rather than methionine, S-adenosyl-L-methionine (AdoMet), or one of its metabolites, acts as the effector of this regulation. To further identify the actual effector, we exploited the wheat germ in vitro translation system. The effects of various metabolites and analogs of AdoMet were tested by using RNA carrying a CGS1 exon 1-reporter fusion. These tests identified AdoMet as the effector of this regulation. S-adenosyl-L-ethionine, an analog of AdoMet, also had effector activity. A. thaliana mto1 mutants, which are deficient in this regulation, showed a much reduced response to AdoMet in vitro, with a leaky allele showing a less reduced response. RNA translated in vitro in the presence of AdoMet contained a 5'-truncated RNA species, similar to the one that we previously suggested was an in vivo degradation intermediate of CGS1 mRNA. Together, the results show that the basic reactions of CGS1 exon 1-mediated posttranscriptional regulation occur in the wheat germ in vitro translation system, and that AdoMet acts as the effector.

SUBMITTER: Chiba Y

PROVIDER: S-EPMC193543 | biostudies-literature | 2003 Sep

REPOSITORIES: biostudies-literature

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S-adenosyl-L-methionine is an effector in the posttranscriptional autoregulation of the cystathionine gamma-synthase gene in Arabidopsis.

Chiba Yukako Y Sakurai Ryoko R Yoshino Michiko M Ominato Kimihiro K Ishikawa Mari M Onouchi Hitoshi H Naito Satoshi S

Proceedings of the National Academy of Sciences of the United States of America 20030821 18

Cystathionine gamma-synthase, the first committed enzyme of methionine biosynthesis in higher plants, is encoded by the CGS1 gene in Arabidopsis thaliana. We have shown previously that the stability of the CGS1 mRNA is negatively regulated in response to methionine application [Chiba, Y., Ishikawa, M., Kijima, F., Tyson, R. H., Kim, J., Yamamoto, A., Nambara, E., Leustek, T., Wallsgrove, R. M. & Naito, S. (1999) Science 286, 1371-1374]. To determine whether methionine itself is the effector of t ...[more]

PMID: 12934018

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Project description:BackgroundThe essential sulfur-containing amino acid methionine plays a vital role in plant metabolism and human nutrition. In this study, we aimed to elucidate the regulatory role of the first committed enzyme in the methionine biosynthesis pathway, cystathionine γ-synthase (CGS), on methionine accumulation in tobacco seeds. We also studied the effect of this manipulation on the seed's metabolism.ResultsTwo forms of Arabidopsis CGS (AtCGS) were expressed under the control of the seeds-specific promoter of legumin B4: feedback-sensitive F-AtCGS (LF seeds), and feedback-insensitive T-AtCGS (LT seeds). Unexpectedly, the soluble content of methionine was reduced significantly in both sets of transgenic seeds. Amino acids analysis and feeding experiments indicated that although the level of methionine was reduced, the flux through its synthesis had increased. As a result, the level of protein-incorporated methionine had increased significantly in LT seeds by up to 60%, but this was not observed in LF seeds, whose methionine content is tightly regulated. This increase was accompanied by a higher content of other protein-incorporated amino acids, which led to 27% protein content in the seeds although this was statistically insignificantly. In addition, the levels of reducing sugars (representing starch) were slightly but significantly reduced, while that of oil was insignificantly reduced. To assess the impact of the high expression level of T-AtCGS in seeds on other primary metabolites, metabolic profiling using GC-MS was performed. This revealed significant alterations to the primary seed metabolism manifested by a significant increase in eight annotated metabolites (mostly sugars and their oxidized derivatives), while the levels of 12 other metabolites were reduced significantly in LT compared to wild-type seeds.ConclusionExpression of T-AtCGS leads to an increase in the level of total Met, higher contents of total amino acids, and significant changes in the levels of 20 annotated metabolites. The high level of oxidized metabolites, the two stress-associated amino acids, proline and serine, and low level of glutathione suggest oxidative stress that occurs during LT seed development. This study provides information on the metabolic consequence of increased CGS activity in seeds and how it affects the seed's nutritional quality.

Project description:Hydrogen sulfide (H2S) has been proposed to exert pro- as well as anti-inflammatory effects in various models of critical illness. In this study, we compared bacterial lipopolysaccharide (LPS)‑induced changes in inflammatory mediator production, indices of multiple organ injury and survival in wild‑type (WT) mice and in mice with reduced expression of one of the three H2S‑producing enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3MST). Mice were injected intraperitoneally (i.p.) with LPS (10 mg/kg). After 6 h, the animals were sacrificed, blood and organs were collected and the following parameters were evaluated: blood urea nitrogen (BUN) levels in blood, myeloperoxidase (MPO) and malondialdehyde (MDA) in the lung, cytokine levels in plasma and the expression of the three H2S‑producing enzymes (CBS, CSE and 3MST) in the spleen, lung, liver and kidney. LPS induced a tissue‑dependent upregulation of some of the H2S‑producing enzymes in WT mice (upregulation of CBS in the spleen, upregulation of 3MST in the liver and upregulation of CBS, CSE and 3MST in the lung). Moreover, LPS impaired glomerular function, as evidenced by increased BUN levels. Renal impairment was comparable in the CSE‑/‑ and Δ3MST mice after LPS challenge; however, it was attenuated in the CBS+/‑ mice. MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) in lung homogenates were significantly increased in response to LPS; these effects were similar in the WT, CBS+/‑, CSE‑/‑ and Δ3MST mice; however, the MDA levels tended to be lower in the CBS+/‑ and CSE‑/‑ mice. LPS induced significant increases in the plasma levels of multiple cytokines [tumor necrosis factor (TNF)α, interleukin (IL)‑1β, IL‑6, IL‑10, IL‑12 and interferon (IFN)γ] in plasma; TNFα, IL‑10 and IL‑12 levels tended to be lower in all three groups of animals expressing lower levels of H2S‑producing enzymes. The survival rates after the LPS challenge did not show any significant differences between the four animal groups tested. Thus, the findings of this study indicate that a deficiency in 3MST does not significantly affect endotoxemia, while a deficiency in CBS or CSE slightly ameliorates the outcome of LPS-induced endotoxemia in vivo.

Dataset Information

S-adenosyl-L-methionine is an effector in the posttranscriptional autoregulation of the cystathionine gamma-synthase gene in Arabidopsis.

Publications

S-adenosyl-L-methionine is an effector in the posttranscriptional autoregulation of the cystathionine gamma-synthase gene in Arabidopsis.

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