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SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers.

Roeder S, Dreschler K, Wirtz M, Cristescu SM, van Harren FJ, Hell R, Piechulla B - Plant Mol. Biol. (2009)

Bottom Line: The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g(-1) fresh weight.Ethylene, which is synthesized from SAM, reached only low levels of 1-2 ppbv in N. suaveolens flowers.It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO).

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Strasse 3, Rostock, Germany.

ABSTRACT
S'adenosyl-L: -methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g(-1) fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1-2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO).

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RNA expression of methionine synthase, SAM synthetase and ACC oxidase in different organs of N. suaveolens. Plant tissues (petal lobes, stigmas, stamens, petal tubes, sepals, leaves, stems, roots) were harvested at 6 pm from 3-month-old plants. RNA was isolated and 5 μg of total RNA was separated on denaturing agarose gels. RNA was blotted and hybridised with NsSAMS1, NsMS1 and NsACO probes (Fig. S3). Blots were rehybridized with 18S rDNA probe to allow normalization. The quantification was based on two independent experiments and duplicated Northern blots. Highest expression levels were set at 100% and relative transcript levels were calculated, SE is indicated (n = 4). Black column: methionine synthase; grey column: SAM synthetase, light grey column: ACC oxidase
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Fig3: RNA expression of methionine synthase, SAM synthetase and ACC oxidase in different organs of N. suaveolens. Plant tissues (petal lobes, stigmas, stamens, petal tubes, sepals, leaves, stems, roots) were harvested at 6 pm from 3-month-old plants. RNA was isolated and 5 μg of total RNA was separated on denaturing agarose gels. RNA was blotted and hybridised with NsSAMS1, NsMS1 and NsACO probes (Fig. S3). Blots were rehybridized with 18S rDNA probe to allow normalization. The quantification was based on two independent experiments and duplicated Northern blots. Highest expression levels were set at 100% and relative transcript levels were calculated, SE is indicated (n = 4). Black column: methionine synthase; grey column: SAM synthetase, light grey column: ACC oxidase

Mentions: The SAM cycle is a fundamental metabolic pathway providing cells and tissues with SAM, methionine and related metabolites. Up to now, only a few investigations have shown the expression of SAM cycle genes in leaves, while no information is available for floral tissues. The isolated SAM cycle genes provide now a good opportunity to study this metabolic pathway in flowers. Gene probes were hybridised to total RNA preparations obtained from 3-month-old plants and tissues harvested at 6 pm. This harvest time point was chosen because preliminary experiments revealed the highest SAM synthetase and methionine synthase expression levels at this time of the day. Northern blots were hybridised with the NsMS1, NsSAMS1 and NsACO probes and examples of the expression levels of the 3000-, 1400- and 1200-nucleotide-long mRNAs, respectively, are shown in Fig. S3. The highest mRNA accumulations of the NsMS1 and NsSAMS1 genes were found in the tissue of petal lobes (=100%) followed by elevated levels in the stigma/styles and stems (Fig. 3). mRNA levels below 20% were measured in the other floral organs, such as stamens, petal tubes, and sepals and in green leaves and roots. NsACO was highly expressed in petal lobe tissue, and transcripts were also present in the stigma/style, petal tubes and stems, mRNA levels were low in other vegetative tissues (leaves and roots). It is remarkable that in the plants grown under these conditions, the highest expressions of all SAM cycle genes (NsMS1, NsSAMS1) were detectable in the tissue of petal lobes.Fig. 3


SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers.

Roeder S, Dreschler K, Wirtz M, Cristescu SM, van Harren FJ, Hell R, Piechulla B - Plant Mol. Biol. (2009)

RNA expression of methionine synthase, SAM synthetase and ACC oxidase in different organs of N. suaveolens. Plant tissues (petal lobes, stigmas, stamens, petal tubes, sepals, leaves, stems, roots) were harvested at 6 pm from 3-month-old plants. RNA was isolated and 5 μg of total RNA was separated on denaturing agarose gels. RNA was blotted and hybridised with NsSAMS1, NsMS1 and NsACO probes (Fig. S3). Blots were rehybridized with 18S rDNA probe to allow normalization. The quantification was based on two independent experiments and duplicated Northern blots. Highest expression levels were set at 100% and relative transcript levels were calculated, SE is indicated (n = 4). Black column: methionine synthase; grey column: SAM synthetase, light grey column: ACC oxidase
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2697359&req=5

Fig3: RNA expression of methionine synthase, SAM synthetase and ACC oxidase in different organs of N. suaveolens. Plant tissues (petal lobes, stigmas, stamens, petal tubes, sepals, leaves, stems, roots) were harvested at 6 pm from 3-month-old plants. RNA was isolated and 5 μg of total RNA was separated on denaturing agarose gels. RNA was blotted and hybridised with NsSAMS1, NsMS1 and NsACO probes (Fig. S3). Blots were rehybridized with 18S rDNA probe to allow normalization. The quantification was based on two independent experiments and duplicated Northern blots. Highest expression levels were set at 100% and relative transcript levels were calculated, SE is indicated (n = 4). Black column: methionine synthase; grey column: SAM synthetase, light grey column: ACC oxidase
Mentions: The SAM cycle is a fundamental metabolic pathway providing cells and tissues with SAM, methionine and related metabolites. Up to now, only a few investigations have shown the expression of SAM cycle genes in leaves, while no information is available for floral tissues. The isolated SAM cycle genes provide now a good opportunity to study this metabolic pathway in flowers. Gene probes were hybridised to total RNA preparations obtained from 3-month-old plants and tissues harvested at 6 pm. This harvest time point was chosen because preliminary experiments revealed the highest SAM synthetase and methionine synthase expression levels at this time of the day. Northern blots were hybridised with the NsMS1, NsSAMS1 and NsACO probes and examples of the expression levels of the 3000-, 1400- and 1200-nucleotide-long mRNAs, respectively, are shown in Fig. S3. The highest mRNA accumulations of the NsMS1 and NsSAMS1 genes were found in the tissue of petal lobes (=100%) followed by elevated levels in the stigma/styles and stems (Fig. 3). mRNA levels below 20% were measured in the other floral organs, such as stamens, petal tubes, and sepals and in green leaves and roots. NsACO was highly expressed in petal lobe tissue, and transcripts were also present in the stigma/style, petal tubes and stems, mRNA levels were low in other vegetative tissues (leaves and roots). It is remarkable that in the plants grown under these conditions, the highest expressions of all SAM cycle genes (NsMS1, NsSAMS1) were detectable in the tissue of petal lobes.Fig. 3

Bottom Line: The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g(-1) fresh weight.Ethylene, which is synthesized from SAM, reached only low levels of 1-2 ppbv in N. suaveolens flowers.It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO).

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Strasse 3, Rostock, Germany.

ABSTRACT
S'adenosyl-L: -methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g(-1) fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1-2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO).

Show MeSH
Related in: MedlinePlus