Journal Article

The Iron-regulated Transporter, MbNRAMP1, Isolated from <i>Malus baccata</i> is Involved in Fe, Mn and Cd Trafficking

Haihua Xiao, Liping Yin, Xuefeng Xu, Tianzhong Li and Zhenhai Han

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 6, pages 881-889
Published in print December 2008 | ISSN: 0305-7364
Published online September 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn178
The Iron-regulated Transporter, MbNRAMP1, Isolated from Malus baccata is Involved in Fe, Mn and Cd Trafficking

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Iron deficiency is one of the most common nutritional disorders in plants, especially in fruit trees grown in calcareous soil. Malus baccata is widely used as an apple rootstock in north China and is highly resistant to low temperatures. There are few studies on iron absorption by this species at the molecular level. It is very important to understand the mechanism of iron uptake and transport in such woody plants. As a helpful tool, the aim of the present study was the cloning and functional analysis of NRAMP (natural resistance-associated macrophage protein) genes from the apple tree in relation to trafficking of micronutrients (Fe, Mn and Cd).

Methods

Reverse transcription-PCR (RT-PCR) combined with RACE (rapid amplification of cDNA ends) was adopted to isolate the full-length NRAMP1 cDNA. Southern blotting was used to test gene copy information, and northern blot was used to detect the gene's expression level. Complementation experiments using the yeast mutant strains DEY1453 and SLY8 were employed to confirm the iron- and manganese-transporting ability of NRAMP1 from apple, and inductively coupled plasma (ICP) spectrometry was used to measure Cd accumulation in yeast. NRAMP1–green fluorescent protein (GFP) fusion protein was used to determine the cellular localization in yeast.

Key Results

A 2090 bp cDNA was isolated and named MbNRAMP1. It encodes a predicted polypeptide of 551 amino acids. MbNRAMP1 exists in the M. baccata genome as a single copy and was expressed mainly in roots. MbNRAMP1 rescued the phenotype of yeast mutant strains DEY1453 and SLY8, and also increased Cd2+ sensitivity and accumulation. MbNRAMP1 expression in yeast was largely influenced by iron status, and the expression pattern of MbNRAMP1–GFP varied with the environmental iron nutrition status.

Conclusions

MbNRAMP1 encodes a functional metal transporter capable of mediating the distribution of ions as well as transport of the micronutrients, Fe and Mn, and the toxic metal, Cd.

Keywords: Apple; cadmium; iron-regulated transporter; iron; manganese; NRAMP1; Malus baccata

Journal Article.  4967 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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