Distinct phenotypes generated by overexpression and suppression of S-adenosyl-L-methionine synthetase reveal developmental patterns of gene silencing in tobacco.

Boerjan, Wout; Bauw, Guy; Montagu, Marc Van; Inzé, Dirk

doi:10.1105/tpc.6.10.1401

Cited by 159 publications

(48 citation statements)

References 36 publications

(41 reference statements)

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“…4). This ubiquitous presence is probably due to the metabolic importance of SAM and is in agreement with the character of 'housekeeping' gene attributed to SAMs [3,25,26]. In spite of its generalized expression, SAMs levels were found to be higher in roots than in leaves and stems (Fig.…”

Section: Discussionsupporting

confidence: 62%

“…Some authors have justified the existence of different genes by the metabolic importance of SAM [26,38]. However, it has been also suggested that a part of the SAMs genes would be expressed constitutively while other copies would be specifically regulated by developmental [3,25], hormonal [21], or environmental factors [6,16], always strictly controlled according to the need of SAM [3].…”

Section: Introductionmentioning

confidence: 99%

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Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

Gómez-Gómez

Carrasco

1996

Plant Mol Biol

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Two cDNA clones coding for S-adenosyl-L-methionine synthase (SAMs, EC 2.5.1.6) have been isolated from a cDNA library of gibberellic acid-treated unpollinated pea ovaries. Both cDNAs were sequenced showing a high degree of identity but coding for different SAMs polypeptides. The presence of two SAMs genes in pea was further confirmed by Southern analysis. Expression of the SAMs genes in the pea plant was found at different levels in vegetative and reproductive tissues. We characterized the expression levels of SAMs genes during the development or senescence of pea ovaries. Northern analysis showed that transcription of SAMs genes in parthenocarpic fruits was upregulated by auxins in the same manner as in fruits from pollinated ovaries. In both pollinated and 2,4-dichlorophenoxyacetic acid-treated ovaries, and benzyladenine, although able to induce parthenocarpic development, did not affect SAMs mRNA levels. These data are consistent with an active participation of auxins in the upregulation of SAMs during fruit setting in pea and suggest that, at the molecular level, parthenocarpic development of pea ovaries is different for gibberellin- and cytokinin-treated ovaries than for auxin-induced parthenocarpic biosynthesis since treatment of the ovaries with aminoethoxyvinylglycine resulted in a delay of senescence and prevention of SAMs mRNA accumulation. A possible mechanism for hormonal regulation of SAMs during ovary development is discussed.

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Section: Discussionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

Gómez-Gómez

Carrasco

1996

Plant Mol Biol

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“…Co-suppression of host genes and transgenes expressing the same coding sequence has now been reported in the case of several plant genes: chalcone synthase [15,19], dihydroflavonol reductase [20], polygalacturonase [18], chitinase [9], phytoene synthase [8], pectinesterase [17], S-adenosyl-L-methionine synthetase [1] and nitrite reductase [22]. Similarly, suppression of reporter transgene expression occurring at each generation has also been reported [3,4,11].…”

Section: Introductionmentioning

confidence: 93%

Field trial analysis of nitrate reductase co-suppression: a comparative study of 38 combinations of transgene loci

Palauqui

Vaucheret

1995

Plant Mol Biol

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Co-suppression of host genes and 35S transgenes encoding nitrate reductase was previously reported in transgenic tobacco plants (Nicotiana tabacum cv. Paraguay or Burley) using either a full-length cDNA or fragments devoid of the 3' and/or 5' UTR. Co-suppression was previously shown to affect a limited fraction of the progeny of one transgenic tobacco line homozygous for a single transgene locus, and the phenomenon occurred at each generation. In this work, 38 combinations of transgene loci derived from 13 independent transgenic lines homozygous for a single transgene locus were field-tested under two different conditions in an attempt to determine the corresponding frequencies of co-suppression, i.e. the percentage of plants showing co-suppression. Each of the 13 homozygous lines exhibited a different frequency of co-suppression, ranging from 0% to 57%. High frequencies were found to be associated with transgene loc carrying a high number of copy of the transgene, suggesting a transgene dose effect. Combinations carrying 2 non-allelic transgene loci in a hemizygous state exhibited frequencies of co-suppression between those of each of the 2 transgene loci in a homozygous state, while combinations carrying 2 non-allelic transgene loci in a homozygous state exhibited frequencies of co-suppression higher than the sum of those of the 2 transgene loci alone in a homozygous state, clearly confirming a transgene dose effect. Co-suppression frequencies were increased when the plants were grown initially in vitro, suggesting some environmental effect. The roles of transgene copy number, number of transgene loci and environmental factors are discussed in the light of a threshold hypothesis.

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“…AdoMet is the major methyl-group donor for numerous transmethylation reactions in both prokaryotes and eukaryotes (Tabor and Tabor 1984;Boerjan et al 1994). Plants produce a multitude of secondary products that include one or more methyl groups added during their biosynthesis by methyltransferases, many of which use AdoMet as the methyl-group donor.…”

Section: Introductionmentioning

confidence: 99%

Salt stress enhances xylem development and expression of S-adenosyl-l-methionine synthase in lignifying tissues of tomato plants

Sánchez‐Aguayo

Rodríguez-Galán²,

García

et al. 2004

Planta

177

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S-Adenosyl-L-methionine synthase (SAM; ATP: L-methionine adenosyltransferase, EC 2.5.1.6) catalyzes the biosynthesis of S-adenosyl-L-methionine (AdoMet), a universal methyl-group donor. This enzyme is induced by salinity stress in tomato (Lycopersicon esculentum Mill.). To elucidate the role of SAM and AdoMet in the adaptation of plants to a saline environment, the expression pattern and histological distribution of SAM was investigated in control and salt-stressed tomato plants. Immunohistochemical analysis showed that SAM proteins were expressed in all cell types and plant organs, albeit with preferential accumulation in lignified tissues. Lignin deposition was estimated by histochemical tests and the extent of tissue lignification in response to salinity was quantified by image analysis. The average number of lignified cells in vascular bundles was significantly greater in plants under salt stress, with a maximal expansion of the lignified area found in the root vasculature. Accordingly, the greatest abundance of SAM gene transcripts and proteins occurred in roots. These results indicate that increased SAM activity correlated with a greater deposition of lignin in the vascular tissues of plants under salinity stress. A model is proposed in which an increased number of lignified tracheary elements in tomato roots under salt stress may enhance the cell-to-cell pathway for water transport, which would impart greater selectivity and reduced ion uptake, and compensate for diminished bulk flow of water and solutes along the apoplastic pathway.

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Distinct phenotypes generated by overexpression and suppression of S-adenosyl-L-methionine synthetase reveal developmental patterns of gene silencing in tobacco.

Cited by 159 publications

References 36 publications

Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

Field trial analysis of nitrate reductase co-suppression: a comparative study of 38 combinations of transgene loci

Salt stress enhances xylem development and expression of S-adenosyl-l-methionine synthase in lignifying tissues of tomato plants

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