Abstract
Essential transition metals and non-essential metals often co-exist in arable soils. In plants, some transition metal transporters, such as the natural resistance-associated macrophage proteins (NRAMPs), poorly selectively transport metals with similar chemical properties whether they are essential or non-essential. In this study, a member of the NRAMP transporter family, TpNRAMP3, was identified from dwarf Polish wheat (Triticum polonicum L.). TpNRAMP3 encodes a plasma membrane-localized protein and was highly expressed in leaf blades and roots at the jointing and booting stages, and in the first nodes at the grain filling stage. Expression of TpNRAMP3 increased sensitivity to Cd and Co, but not Zn, and increased the Cd and Co concentrations in yeast. TpNRAMP3 expression in Arabidopsis increased concentrations of Cd, Co, and Mn, but not Fe or Zn, in roots, shoots, and whole plant. However, TpNRAMP3 did not affect translocation of Cd, Co, or Mn from roots to shoots. These results suggest that TpNRAMP3 is a transporter for Cd, Co, and Mn accumulation, but not for Fe or Zn. However, Cd and Co are non-essential toxic metals; selective genetic manipulation of TpNRAMP3 will help breed low Cd- and Co-accumulating cultivars.
Highlights
Essential transition metals, such as Fe, Zn, Mn, and Cu, are cofactors of numerous plant proteins and enzymes; they are required for plant growth and development (Thomine et al, 2000; Lin and Aarts, 2012; Yamaji et al, 2013)
The expression pattern of TpNRAMP3 was investigated in different tissues at three growth stages of wheat grown in a field
Green fluorescence from the fusion protein (HBT95-TpNRAMP3-green fluorescence protein (GFP)) was mostly merged with the red fluorescence of the membrane marker, which indicated that cells were expressing TpNRAMP3 or transformed with pYES2 TpNRAMP3 was localized at the plasma membrane (Figure 2). (Supplementary Figure S4)
Summary
Essential transition metals, such as Fe, Zn, Mn, and Cu, are cofactors of numerous plant proteins and enzymes; they are required for plant growth and development (Thomine et al, 2000; Lin and Aarts, 2012; Yamaji et al, 2013). Some transition metal transporters, such as natural resistance-associated macrophage proteins (NRAMPs) and ironregulated transporters (IRTs), poorly selectively transport metals with similar chemical properties whether they are essential or non-essential (Nevo and Nelson, 2006; Sasaki et al, 2012; Barberon et al, 2014; Pottier et al, 2015). Among the identified AtNRAMPs, AtNRAMP1, AtNRAMP3, and AtNRAMP4 all transport Fe, Mn, and Cd (Curie et al, 2000; Thomine et al, 2000, 2003; Lanquar et al, 2005, 2010; Cailliatte et al, 2010; Pottier et al, 2015). AtNRAMP1 functions in metal uptake of Cd, Fe, and Mn (Curie et al, 2000; Thomine et al, 2000, 2003; Lanquar et al, 2005, 2010; Cailliatte et al, 2009)
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