Isolation and characterization of two cDNA clones encoding ATP‐sulfurylases from potato by complementation of a yeast mutant

• Published in: The Plant journal : for cell and molecular biology Vol. 6; no. 1; pp. 105 - 112
• Main Authors: Klonus, Dirk, Höfgen, Rainer, Willmitzer, Lothar, Riesmeier, Jörg W.
• Format: Journal Article
• Language: English
• Published: Osney Mead, Oxford OX2 0EL, UK Blackwell Science Ltd 01-07-1994; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Base Sequence; Biological and medical sciences; Cloning, Molecular; DNA, Complementary - chemistry; DNA, Complementary - isolation & purification; DNA, Complementary - metabolism; Escherichia coli; Fundamental and applied biological sciences. Psychology; Genetic Complementation Test; Metabolism; Metabolism. Physicochemical requirements; Molecular Sequence Data; Plant physiology and development; Recombinant Proteins - biosynthesis; Recombinant Proteins - metabolism; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Sequence Homology, Amino Acid; Solanum tuberosum; Solanum tuberosum - enzymology; Solanum tuberosum - genetics; Sulfate Adenylyltransferase - biosynthesis; Sulfate Adenylyltransferase - genetics; Sulfate Adenylyltransferase - metabolism; Transformation, Genetic; Assimilation; Sulfates; Fungi; Enzymatic activity; Dicotyledones; Blotting assay; Angiospermae; Tuber; Ascomycetes; Solanaceae; Localization; Sulfur; Aminoacid sequence; Thallophyta; Culture medium; Genetic transformation; Nucleotide sequence; Enzyme; Solanum tuberosum; Gene expression; Open reading frame; Complementary DNA; Vegetative apparatus; Isolation; Spermatophyta; Tuber plant; Mutation; Saccharomyces cerevisiae
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1994.6010105.x

Summary
Sulfur plays an important role in plants, being used for the biosynthesis of amino acids, sulfolipids and secondary metabolites. After uptake sulfate is activated and subsequently reduced to sulfide or serves as donor for sulfurylation reactions. The first step in the activation of sulfate in all cases studied so far is catalyzed by the enzyme ATP‐sulfurylase (E.C. 2.7.7.4.) which catalyzes the formation of adenosine‐5′‐phosphosulfate (APS). Two cDNA clones from potato encoding ATP‐sulfurylases were identified following transformation of a Saccharomyces cerevisiae mutant deficient in ATP‐sulfurylase activity with a cDNA library from potato source leaf poly(A)+ RNA cloned in a yeast expression vector. Several transformants were able to grow on a medium with sulfate as the only sulfur source, this ability being strictly linked to the presence of two classes of cDNAs. The clones StMet3‐1 and StMet3‐2 were further analyzed. DNA analysis revealed an open reading frame encoding a protein with a molecular mass of 48 kDa in the case of StMet3‐1 and 52 kDa for StMet3‐2. The deduced polypeptides are 88% identical at the amino acid level. The clone StMet3‐2 has a 48 amino acid N‐terminal extension which shows common features of a chloroplast transit peptide. Sequence comparison of the ATP‐sulfurylase Met3 from Saccharomyces cerevisiae with the cDNA StMet3‐1 (StMet3‐2) reveals 31% (30%) identity at the amino acid level. Protein extracts from the yeast mutant transformed with the clone StMet3‐1 displayed ATP‐sulfurylase activity. RNA blot analysis demonstrated the expression of both genes in potato leaves, root and stem, but not in tubers. To the best of the authors' knowledge this is the first cloning and identification of genes involved in the reductive sulfate assimilation pathway from higher plants.