O-Acetylserine and the Regulation of Expression of Genes Encoding Components for Sulfate Uptake and Assimilation in Potato

• Published in: Plant physiology (Bethesda) 2005-05, Vol.138 (1), p.433-440
• Main Authors: Hopkins, Laura, Parmar, Saroj, Błaszczyk, Anna, Hesse, Holger, Hoefgen, Rainer, Hawkesford, Malcolm J
• Format: Article
• Language: English
• Subjects: acetylserine; Acetyltransferases - genetics; Acetyltransferases - metabolism; adenylyl-sulfate reductase; assimilation (physiology); Base Sequence; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Biological Transport; Blotting, Northern; Cell physiology; complementary DNA; DNA Primers; DNA, Complementary - isolation & purification; DNA, Plant - genetics; Escherichia coli; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gene Expression Regulation, Plant; gene overexpression; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Messenger RNA; Molecular and cellular biology; Molecular Sequence Data; nucleotide sequences; nutrient uptake; oxidoreductases; Physiological assimilation; plant biochemistry; plant genetics; plant proteins; Plant roots; Plant Roots - metabolism; Plants; Plants, Genetically Modified; potatoes; Serine - analogs & derivatives; Serine - metabolism; Serine O-Acetyltransferase; Signal transduction; soil nutrients; Solanum tuberosum; Solanum tuberosum - genetics; Solanum tuberosum - metabolism; Starvation; sulfate transporter; Sulfates; Sulfates - metabolism; Sulfides; Sulfur; transcription (genetics); Transgenic plants; transporters
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.057521

cDNAs encoding a high-affinity sulfate transporter and an adenosine 5'-phosphosulfate reductase from potato (Solanum tuberosum L. cv Désirée) have been cloned and used to examine the hypothesis that sulfate uptake and assimilation is transcriptionally regulated and that this is mediated via intracellular O-acetylserine (OAS) pools. Gas chromotography coupled to mass spectrometry was used to quantify OAS and its derivative, N-acetylserine. Treatment with external OAS increased sulfate transporter and adenosine 5'-phosphosulfate reductase gene expression consistent with a model of transcriptional induction by OAS. To investigate this further, the Escherichia coli gene cysE (serine acetyltransferase EC 2.3.1.30), which synthesizes OAS, has been expressed in potato to modify internal metabolite pools. Transgenic lines, with increased cysteine and glutathione pools, particularly in the leaves, had increased sulfate transporter expression in the roots. However, the small increases in the OAS pools were not supportive of the hypothesis that this molecule is the signal of sulfur (S) nutritional status. In addition, although during S starvation the content of S-containing compounds decreased (consistent with derepression as a mechanism of regulation), OAS pools increased only following extended starvation, probably as a consequence of the S starvation. Taken together, expression of these genes may be induced by a demand-driven model, via a signal from the shoots, which is not OAS. Rather, the signal may be the depletion of intermediates of the sulfate assimilation pathway, such as sulfide, in the roots. Finally, sulfate transporter activity did not increase in parallel with transcript and protein abundance, indicating additional posttranslational regulatory mechanisms.