Identification and characterization of the zinc-regulated transporters, iron-regulated transporter-like protein (ZIP) gene family in maize

Abstract

BackgroundZinc (Zn) and iron (Fe) are essential micronutrients for plant growth and development, their deficiency or excess severely impaired physiological and biochemical reactions of plants. Therefore, a tightly controlled zinc and iron uptake and homeostasis network has been evolved in plants. The Zinc-regulated transporters, Iron-regulated transporter-like Proteins (ZIP) are capable of uptaking and transporting divalent metal ion and are suggested to play critical roles in balancing metal uptake and homeostasis, though a detailed analysis of ZIP gene family in maize is still lacking.ResultsNine ZIP-coding genes were identified in maize genome. It was revealed that the ZmZIP proteins share a conserved transmembrane domain and a variable region between TM-3 and TM-4. Transiently expression in onion epidermal cells revealed that all ZmZIP proteins were localized to the endoplasmic reticulum and plasma membrane. The yeast complementation analysis was performed to test the Zn or Fe transporter activity of ZmZIP proteins. Expression analysis showed that the ZmIRT1 transcripts were dramatically induced in response to Zn- and Fe-deficiency, though the expression profiles of other ZmZIP changed variously. The expression patterns of ZmZIP genes were observed in different stages of embryo and endosperm development. The accumulations of ZmIRT1 and ZmZIP6 were increased in the late developmental stages of embryo, while ZmZIP4 was up-regulated during the early development of embryo. In addition, the expression of ZmZIP5 was dramatically induced associated with middle stage development of embryo and endosperm.ConclusionsThese results suggest that ZmZIP genes encode functional Zn or Fe transporters that may be responsible for the uptake, translocation, detoxification and storage of divalent metal ion in plant cells. The various expression patterns of ZmZIP genes in embryo and endosperm indicates that they may be essential for ion translocation and storage during differential stages of embryo and endosperm development. The present study provides new insights into the evolutionary relationship and putative functional divergence of the ZmZIP gene family during the growth and development of maize.

Spatially resolved analysis of variation in barley (Hordeum vulgare) grain micronutrient accumulation

“…The strongest correlation was found between Zn and Fe with 46.5% of the variation in Fe concentration being explained by the Zn concentration of the grain. These strong correlations have been reported before for wheat and pearl millet grains (Cakmak et al ., ; Jiang et al ., ; Morgounov et al ., ; Peleg et al ., ; Zhao et al ., ; Chatzav et al ., ) and could be attributable to the limited specificity of transporters and metal ligands for either Zn or Fe (Tauris et al ., ; Li et al ., ; Borrill et al ., ; Slamet‐Loedin et al ., ).…”

Evolutionary analysis of iron (Fe) acquisition system in Marchantia polymorpha

“…In this study, we found that the liverwort M. polymorpha uses the reduction‐based strategy I for Fe acquisition. Nongraminaceous and some graminaceous plants, including rice and maize, use this strategy for Fe acquisition (Ishimaru et al ., ; Li et al ., ). Therefore, the Fe acquisition mechanism in M. polymorpha may be comparable to that in angiosperms.…”

Comparative and phylogenetic analysis of zinc transporter genes/proteins in plants

“…Studies have reported that ZIP proteins have similar topology with eight potential TM domains and they contain a variable cytoplasmic region between TM-3 and TM-4, including a potential His-rich metal-binding domain (Guerinot, 2000;Lopez-Millan et al, 2004;Li et al, 2013). In addition, TM-2, -4, and -5 were reported to contain a fully conserved histidine residue in all family members (Grotz et al, 1998;Guerinot, 2000).…”

“…However, TM-4 was demonstrated to be the most conserved site of ZIP proteins, which, with an adjacent (semi)polar residue, may form part of the intramembranous metal-binding site in the transport pathway (Eng et al, 1998). Zn transporter gene homologs have also been characterized in some plant species, including soybean (Moreau et al, 2002), rice (Ramesh et al, 2003;Ishimaru et al, 2005), Medicago truncatula (LopezMillan et al, 2004), and maize (Li et al, 2013). Although Zn transporters have been identified in some plants, we still lack knowledge in many plant species.…”