The role of ZIP transporters and group F bZIP transcription factors in the Zn‐deficiency response of wheat (Triticum aestivum)

Abstract

SummaryUnderstanding the molecular basis of zinc (Zn) uptake and transport in staple cereal crops is critical for improving both Zn content and tolerance to low‐Zn soils. This study demonstrates the importance of group F bZIP transcription factors and ZIP transporters in responses to Zn deficiency in wheat (Triticum aestivum). Seven group F TabZIP genes and 14 ZIPs with homeologs were identified in hexaploid wheat. Promoter analysis revealed the presence of Zn‐deficiency‐response elements (ZDREs) in a number of the ZIPs. Functional complementation of the zrt1/zrt2 yeast mutant by TaZIP3, ‐6, ‐7, ‐9 and ‐13 supported an ability to transport Zn. Group F TabZIPs contain the group‐defining cysteine–histidine‐rich motifs, which are the predicted binding site of Zn2+ in the Zn‐deficiency response. Conservation of these motifs varied between the TabZIPs suggesting that individual TabZIPs may have specific roles in the wheat Zn‐homeostatic network. Increased expression in response to low Zn levels was observed for several of the wheat ZIPs and bZIPs; this varied temporally and spatially suggesting specific functions in the response mechanism. The ability of the group F TabZIPs to bind to specific ZDREs in the promoters of TaZIPs indicates a conserved mechanism in monocots and dicots in responding to Zn deficiency. In support of this, TabZIPF1‐7DL and TabZIPF4‐7AL afforded a strong level of rescue to the Arabidopsis hypersensitive bzip19 bzip23 double mutant under Zn deficiency. These results provide a greater understanding of Zn‐homeostatic mechanisms in wheat, demonstrating an expanded repertoire of group F bZIP transcription factors, adding to the complexity of Zn homeostasis.

A high activity zinc transporter OsZIP9 mediates zinc uptake in rice

“…The ZIP family is regarded as the primary group of transporters controlling Zn influx locating at the plasma membrane (Grotz et al, 1998;Tiong et al, 2014;Evens et al, 2017). To identify transporters responsible for Zn uptake in rice roots, we first investigated the Zn transport activity of 14 ZIP members using heterologous expression assays in a yeast mutant strain ZHY3 (Dzrt1zrt2) defective in Zn uptake.…”

Potential of microbes in the biofortification of Zn and Fe in dietary food grains. A review

“…There are several metal transporters in plants, including a zinc-regulated transporter (ZRT)/iron-regulated transporter (IRT)-like protein (ZIP) family, which is involved in the translocation of Zn and Fe, a cation diffusion facilitator (CDF) family, and a P-type ATPase family involved in xylem loading of Zn as well as other heavy metals (Colangelo and Guerinot 2006;Eide 2006). The ZIP family proteins have been reported in rice, wheat, maize, and Arabidopsis thaliana (Evens et al 2017;Grotz et al 1998;Ishimaru et al 2005;Krämer et al 2007;Xu et al 2010). The overexpression of these proteins led to an accumulation of excess amounts of Zn in the cells of wild emmer wheat (Durmaz et al 2011).…”

Transcriptome profiles of soybean leaves and roots in response to zinc deficiency

“…Arabidopsis F‐group bZIP TF bZIP19 and bZIP23 have been shown to be essential for the Zn homeostasis regulation (Assunção et al , Inaba et al ). The F‐group bZIP TFs in other plants such as wheat and barley were also found to have a similar function in Zn‐deficiency response (Castro et al , Evens et al , Nazri et al ). There are also two members of F‐group bZIP TFs in soybean genome, GmbZIP121 ( Gm11g108100 ) and GmbZIP122 ( Gm12g033000 ) (Liao et al ).…”

“…The F-group bZIP TFs in other plants such as wheat and barley were also found to have a similar function in Zn-deficiency response (Castro et al 2017, Evens et al 2017, Nazri et al 2017. There are also two members of F-group bZIP TFs in soybean genome, GmbZIP121 (Gm11g108100) and GmbZIP122 (Gm12g033000) (Liao et al 2008).…”