Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase.

Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase. Research Abstract Details 

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Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase. Abstract Text:

J Rinder,A P Casazza,R Hoefgen,H Hesse,

The availability of the carbon backbone O-phosphohomoserine (OPHS) is critical to methionine (met) and threonine (thr) synthesis. OPHS derives from homoserine and is formed by homoserine kinase (HSK). To clarify the function of HSK in cellular metabolism, the E. coli HSK ortholog thrB was expressed in potato plants targeting the EcHSK protein to chloroplasts and to the cytosol. Both approaches resulted in up to 11 times increased total HSK enzyme activity. Transgenic plants exhibited reduced homoserine levels while met and thr did not accumulate significantly. However, the precursor cysteine and upstream intermediates of met such as cystathionine and homocysteine did indicating an accelerated carbon flow towards the end products. Coincidently, plants with elevated cytosolic levels of EcHSK exhibited a reduction in transcript levels of the endogenous HSK, as well as of threonine synthase (TS), cystathionine beta-lyase (CbL), and met synthase (MS). In all plants, cystathionine gamma-synthase (CgS) expression remained relatively unchanged from wild type levels, while S-adenosylmethionine synthetase (SAMS) expression increased. Feeding studies with externally supplied homoserine fostered the synthesis of met and thr but the regulation of synthesis of both amino acids retained the wild type regulation pattern. The results indicate that excess of plastidial localised HSK activity does not influence the de novo synthesis of met and thr. However, expression of HSK in the cytosol resulted in the down-regulation of gene expression of pathway genes probably mediated via OPHS. We integrated these data in a novel working model describing the regulatory mechanism of met and thr homeostasis.

Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase. Publishing Authors By Initials

J Rinder,AP Casazza,R Hoefgen,H Hesse,

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Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Amino acids

VOLUME: 34

Page Numbers: 213-22

Journal Abbreviation: Amino Acids

ISSN: 1438-2199

DAY: 12

MONTH: 07

YEAR: 2007

Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase. Information

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LANGUAGE: eng

NlmUniqueID: 9200312

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Grant and Affiliation Information for Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase.

AFFILIATION: Department of Molecular Physiology, Max-Planck-Institut für Molekulare Pflanzenphysiologie, Golm, Germany.

Country: Austria

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MEDLINETA: Amino Acids

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