The Nramp family of transition metal transporters in Arabidopsis thaliana

Vaughan, Russell John (2004) The Nramp family of transition metal transporters in Arabidopsis thaliana. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Analysis of the AtNramp sequences and comparison to other Nramps suggests that they contain 12 transmembrane domains and a conserved signature motif implicated in transport activity. The tissue-specific expression patterns of the AtNramp genes have been studied using RT-PCR and quantitative PCR performed on root, leaf, stem, flower and silique material. The AtNramps were detected in all tissues with the exception of AtNramp5, which was only found in flowers. Upon Fe starvation, AtNramp3 transcript increased in roots while AtNramp6 increased in stem. No changes were observed in other AtNramp genes. The function of the AtNramps has been studied using yeast mutants deficient in Fe uptake. AtNramp3 and AtNramp4 were able to rescue the fet3/fet4 Fe uptake mutant while AtNramp5 and AtNramp6 have not successfully complemented this mutant. Radiolabelled Fe uptake assays in the same cells showed that AtNramp3 and Atnramp4 are capable of transporting Fe and that this transport is pH dependent in AtNramp4 transformed cells. A lower level of uptake activity was also observed with AtNramp5 in some experiments. Plant lines containing T-DNA inserts with the AtNramp genes have been identified in order to allow the future investigation of the effect of lack of function of the AtNramps. The data presented suggest that members of the AtNramp family play different roles in transition metal homeostasis in Arabidopsis thaliana.