title: Structural and functional characterization of AtPTR3, a stress-induced peptide transporter of Arabidopsis.
abstract: A T-DNA tagged mutant line of Arabidopsis thaliana, produced with a promoter trap vector carrying a promoterless gus (uidA) as a reporter gene, showed GUS induction in response to mechanical wounding. Cloning of the chromosomal DNA flanking the T-DNA revealed that the insert had caused a knockout mutation in a PTR-type peptide transporter gene named At5g46050 in GenBank, here renamed AtPTR3. The gene and the deduced protein were characterized by molecular modelling and bioinformatics. Molecular modelling of the protein with fold recognition identified 12 transmembrane spanning regions and a large loop between the sixth and seventh helices. The structure of AtPTR3 resembled the other PTR-type transporters of plants and transporters in the major facilitator superfamily. Computer analysis of the AtPTR3 promoter suggested its expression in roots, leaves and seeds, complex hormonal regulation and induction by abiotic and biotic stresses. The computer-based hypotheses were tested experimentally by exposing the mutant plants to amino acids and several stress treatments. The AtPTR3 gene was induced by the amino acids histidine, leucine and phenylalanine in cotyledons and lower leaves, whereas a strong induction was obtained in the whole plant upon exposure to salt. Furthermore, the germination frequency of the mutant line was reduced on salt-containing media, suggesting that the AtPTR3 protein is involved in stress tolerance in seeds during germination.
authors.affiliation: School of Life Sciences, University of Skövde, 541 28 Skövde, Sweden.
authors.forename: Sazzad
authors.initials: S
authors.lastname: Karim
authors.forename: Dan
authors.initials: D
authors.lastname: Lundh
authors.forename: Kjell-Ove
authors.initials: KO
authors.lastname: Holmström
authors.forename: Abul
authors.initials: A
authors.lastname: Mandal
authors.forename: Minna
authors.initials: M
authors.lastname: Pirhonen
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D030561:Databases, Nucleic Acid; D005786:Gene Expression Regulation / Q000187:drug effects; D018525:Germination / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D008958:Models, Molecular; D011487:Protein Conformation; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; C510826:PTR3 protein, Arabidopsis; D012965:Sodium Chloride