Two cDNAs from potato are able to complement a phosphate uptake-deficient yeast mutant: identification of phosphate transporters from higher plants

• Published in: The Plant cell Vol. 9; no. 3; pp. 381 - 392
• Main Authors: Leggewie, G. (Max-Planck-Institut fur Molekulare Pflanzenpysiologie, Golm, Germany.), Willmitzer, L, Riesmeier, J.W
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Physiologists 01-03-1997
• Subjects: ABSORCION DE SUSTANCIAS NUTRITIVAS; ABSORPTION DE SUBSTANCES NUTRITIVES; ADN; Amino Acid Sequence; Amino acids; ANION; ANIONES; ARN MENSAJERO; ARN MESSAGER; Carrier Proteins - biosynthesis; Carrier Proteins - chemistry; Carrier Proteins - genetics; Complementary DNA; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; DISPONIBILIDAD DE NUTRIENTES; DISPONIBILITE D'ELEMENT NUTRITIF; DNA, Complementary - metabolism; DNA, Plant - metabolism; ESTRUCTURA CELULAR; EXPRESION GENICA; EXPRESSION DES GENES; FOSFATOS; Genetic Complementation Test; GENETICA; GENETIQUE; ION; IONES; Kinetics; Molecular Sequence Data; MUTACION; MUTANT; MUTANTES; MUTATION; PHOSPHATE; Phosphate transport proteins; Phosphate-Binding Proteins; Phosphates; Phosphates - metabolism; Plant cells; Plant roots; Plants; Protein Structure, Secondary; PROTEINAS VEGETALES; PROTEINE VEGETALE; Proteins; Proton-Phosphate Symporters; RACINE; RAICES; Recombinant Proteins - biosynthesis; RNA; SACCHAROMYCES CEREVISIAE; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; SECUENCIA NUCLEOTIDICA; Sequence Homology, Amino Acid; SEQUENCE NUCLEOTIDIQUE; SOLANUM TUBEROSUM; Solanum tuberosum - genetics; Solanum tuberosum - metabolism; STRUCTURE CELLULAIRE; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.9.3.381

Acquisition as well as translocation of phosphate are essential processes for plant growth. In many plants, phosphate uptake by roots and distribution within the plant are presumed to occur via a phosphate/proton cotransport mechanism. Here, we describe the isolation of two cDNAs, StPT1 and StPT2, from potato (Solanum tuberosum) that show homology to the phosphate/proton cotransporter PHO84 from the yeast Saccharomyces cerevisiae. The predicted products of both cDNAs share 35% identity with the PHO84 sequence. The deduced structure of the encoded proteins revealed 12 membrane-spanning domains with a central hydrophilic region. The molecular mass was calculated to be 59 kD for the StPT1 protein and 58 kD for the StPT2 protein. When expressed in a PHO84-deficient yeast strain, MB192, both cDNAs complemented the mutant. Uptake of radioactive orthophosphate by the yeast mutant expressing either StPT1 or StPT2 was dependent on pH and reduced in the presence of uncouplers of oxidative phosphorylation, such as 2,4-dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone. The Km for Pi uptake of the StPT1 and StPT2 proteins was determined to be 280 and 130 micromolar, respectively. StPT1 is expressed in roots, tubers, and source leaves as well as in floral organs. Deprivation of nitrogen, phosphorus, potassium, and sulfur changed spatial expression as well as the expression level of StPT1. StPT2 expression was detected mainly in root organs when plants were deprived of Pi and to a lesser extent under sulfur deprivation conditions. No expression was found under optimized nutrition conditions or when other macronutrients were lacking