The exuT gene of Erwinia chrysanthemi EC16: nucleotide sequence, expression, localization, and relevance of the gene product

• Published in: Molecular plant-microbe interactions Vol. 11; no. 4; pp. 270 - 276
• Main Authors: Haseloff, B.J, Freeman, T.L, Valmeekam, V, Melkus, M.W, Oner, F, Valachovic, M.S, San Francisco, M.J.D
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01-04-1998; The American Phytopathological Society
• Subjects: Amino Acid Sequence; AMINO ACID SEQUENCES; ARN MENSAJERO; ARN MESSAGER; AZUCARES ACIDOS; Bacterial plant pathogens; Bacterial Proteins - genetics; Bacteriology; Base Sequence; Biological and medical sciences; CELL MEMBRANES; CELL WALLS; CHEMICAL COMPOSITION; CHEMISTRY; CHIMIE; CITOPLASMA; Cloning, Molecular; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; CYTOPLASM; CYTOPLASME; DNA, Bacterial - genetics; ERWINIA CHRYSANTHEMI; EXPRESION GENICA; EXPRESSION DES GENES; Fundamental and applied biological sciences. Psychology; GALACTURONIC ACID; GENBANK/U35884; GENE; GENE EXPRESSION; GENES; Genes, Bacterial; Genetics; HISTOCHEMISTRY; IMMUNOCYTOCHEMISTRY; IMMUNOLOGIE; IMMUNOLOGY; INFECCION; INFECTION; INMUNOLOGIA; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; Membrane Proteins - genetics; MESSENGER RNA; Microbiology; MOLECULAR SEQUENCE DATA; MOLECULAR WEIGHT; Mutation; NUCLEOTIDE SEQUENCE; PARED CELULAR; PAROI CELLULAIRE; Pectobacterium chrysanthemi - genetics; Pectobacterium chrysanthemi - pathogenicity; PESO MOLECULAR; Phytopathology. Animal pests. Plant and forest protection; plant disease; Plant Diseases - microbiology; POIDS MOLECULAIRE; POLIGALACTURONASA; POLYGALACTURONASE; PROTEINAS; PROTEINE; PROTEINS; QUIMICA; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE; SOLANUM TUBEROSUM; Solanum tuberosum - microbiology; SUCRE ACIDE; SUGAR ACIDS; Systematics. Structure, properties and multiplication. Genetics; TUBERCULE; TUBERCULO; TUBERS; UPTAKE; Membrane protein; Plant pathogen; Nucleotide sequence; Gene expression; Uptake; Membrane transport; DNA; Erwinia chrysanthemi; Bacteria; Galacturonic acid; Carrier protein; Aminoacid sequence; Enterobacteriaceae
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI.1998.11.4.270

Galacturonic acid (GalUA) is a major component of pectin and polygalacturonic acid in the plant cell wall. In the phytopathogen Erwinia chrysanthemi, the uptake of molecules derived from degradation of these polymers is an important early step in the events preceding induction of pectinases, ultimately leading to plant tissue maceration. Uptake systems for GalUA and dimers of GalUA have been described and shown to be inducible in E. chrysanthemi. The GalUA uptake gene (exuT) was cloned and sequenced. Nucleotide sequence analysis identified an open reading frame encoding a 345-amino-acid polypeptide with a calculated mass of 37,825 Da. This polypeptide is predicted to be an integral membrane protein based on its high nonpolar amino acid content and hydropathic profile. Localization studies with the labeled polypeptide in the T7-RNA polymerase system also suggest that ExuT is a membrane protein. This evidence is further supported by the observation of hybrid ExuT-PhoA proteins in the bacterial cytoplasmic membrane following immunoblot analysis. Northern (RNA) analysis indicated that the gene is inducible in the presence of the monomer, GalUA. A targeted mutation in the exuT gene affected the utilization of GalUA as a sole carbon source for growth. Maceration of potato tuber tissue by this mutant was delayed and reduced, when compared with the parental strain EC16