Abstract
BackgroundPlant ZIP genes represent an important transporter family involved in metal transport. Evidence has implied that some ZIPs may contribute to plant Cd uptake, but a genome-wide examination of ZIPs’ role in Cd tolerance and uptake has rarely been reported. In this study, a genome-wide bioinformatic screening of candidate ZIP genes in Arabidopsis and rice was performed, followed by a systematic determination of their expression profile in response to Cd stress. Typical up-regulated ZIPs genes were then expressed in yeast cells to examine their effect on hosts’ Cd uptake.ResultsA total of 27 ZIP genes in Arabidopsis and rice were screened out based on sequence similarity. In Arabidopsis, Cd exposure strongly impacted the expression of most ZIPs, among which AtIRT1, AtIRT2, AtIRT4 AtZIP9, AtZIP10 and AtZIP12 were sharply up-regulated and AtIRT3, AtIRT5 were significantly down-regulated in root. In rice, all tested genes in shoot except for OsIRT1 and OsIRT12 were sharply up-regulated, while OsIRT1 and OsZIP1 in root were significantly down-regulated. Interestingly, some genes like AtIRT3, AtZIP5, AtZIP12, OsIRT1 and OsZIP1 showed converse expression regulation when subject to the tested Cd stress. When expressed in yeast cells, three ZIPs, AtIRT1, OsZIP1 and OsZIP3, caused a substantial increase in Cd sensitivity and Cd accumulation of the host cells.ConclusionsIn conclusion, this study revealed a distinct pattern in ZIPs family genes expression between Arabidopsis and rice in response to Cd stress. Arabidopsis mainly up-regulated root ZIPs genes, while rice mainly up-regulated shoot ZIPs genes. Three genes, AtIRT1, OsZIP1 and OsZIP3, conferred an increased Cd accumulation and sensitivity to Cd stress when expressed in yeast cells, further implying their roles in Cd uptake in plants.
Highlights
Plant zinc(Zn)-regulated/iron(Fe)-regulated transporter-like family proteins (ZIPs) genes represent an important transporter family involved in metal transport
In this study, 15 candidate ZIP genes from Arabidopsis and 12 from rice were screened out based on sequence similarity
These ZIP-like genes seem to be phylogenetically distant from SpZRT1 and AtIRT1 and were not tested in this study
Summary
Plant ZIP genes represent an important transporter family involved in metal transport. The zinc(Zn)-regulated/iron(Fe)-regulated transporterlike family proteins (ZIPs) are membrane-located proteins for cations transport (Eng et al 1998; Guerinot 2000). They have been found to exist broadly in prokaryotic cells, fungi, plants and mammalians. Arabidopsis IRT1 is a well-studied ZIP gene first identified as a crucial transporter for plant Fe uptake. Biological functions in Zn/ Fe transport of AtIRT2 (Vert et al 2001, 2009), AtZIP1/2 (Grotz et al 1998; Wintz et al 2003; Milner et al 2013), OsIRT1 (Nakanishi et al 2006; Lee and An 2009; Ishimaru et al 2006; Bughio et al 2002) and OsZIP4/5/8 (Ishimaru et al 2005; Chen et al 2008; Lee et al 2010a, b; Yang et al 2009) have been examined in the past decade
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