Structural and functional characterization of AtPT

Authors: Sazzad Karim Dan Lundh KjellOve Holmström Abul Mandal Minna Pirhonen

Publish Date: 2005/05/12

Volume: 11, Issue: 3, Pages: 226-236

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Abstract

A TDNA 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 TDNA revealed that the insert had caused a knockout mutation in a PTRtype 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 PTRtype 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 computerbased 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 saltcontaining media suggesting that the AtPTR3 protein is involved in stress tolerance in seeds during germination

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