ARS | Publication request: Expression and cellular localization of ZIP1 transporter under zinc-deficiency in wild emmer wheat

Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 30, 2010
Publication Date: September 1, 2011
Citation: Durmaz, E., Coruh, C., Dinler, G., Grusak, M.A., Peleg, Z., Saranga, Y., Fahima, T., Yazici, A., Ozturk, L., Cakmak, I., Budak, H. 2011. Expression and cellular localization of ZIP1 transporter under zinc-deficiency in wild emmer wheat. Plant Molecular Biology Reporter. 29(3):582-596.

Interpretive Summary: In cereal crops, zinc deficiency is a common problem leading to severe decreases in grain yield and has detrimental effects on the nutritional quality of seeds. Wild emmer wheat, which often is found to grow in zinc-limited soils, exhibits a potential genetic resource for wheat improvement due to its ability to be inter-bred with modern wheat. In this study, zinc deficiency responses of wild progenitors and modern wheats were examined using approaches with plants grown using various zinc concentrations. The results revealed wide variation in response to zinc deficiency in wild emmer plants. We found differences in the expression of a specific plant protein (ZIP1), between the diverse wild and modern wheat lines, with some of the wild wheats showing higher ZIP1 expression and better growth at low zinc conditions. These results demonstrate that wild wheats could serve as a source of zinc-related genes with the potential to improve tolerance to zinc deficiency in modern wheats.

Technical Abstract: Zinc (Zn) deficiency is a common problem leading to severe decreases in grain yield and has detrimental effects on nutritional quality in cereals. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, exhibits a potential genetic resource for wheat improvement due to its compatibility with modern wheat. In this study, Zn deficiency response of wild progenitors and modern wheats were examined using molecular and physiological approaches with plants grown under various Zn concentrations. The results revealed wide variation in response to Zn deficiency between wild emmer accessions. Amongst the wild emmer accessions studied, accession MM 5/4 was found to be most tolerant and accession 19-36 was the most sensitive to Zn deficiency. To better understand Zn transport mechanisms in wild emmer wheat, we analyzed the expression patterns of a ZRT/IRT like protein, ZIP1, in the roots and shoots of several accessions that were maintained on different concentrations of Zn. Quantitative real-time PCR (qRT-PCR) results revealed that ZIP1 transcript levels are elevated with decreasing Zn supply in all accessions. Particularly, ZIP1 transcript accumulation was lower in the roots of accession MM 5/4 while the susceptible, 19-36 accession, has elevated levels of ZIP1 transcript, revealing a Zn deficiency response for this genotype. We also identified and cloned a full-length ZIP1 transporter, named, TdZIP1 and further analyzed the corresponding protein sequence for structural attributes. Under Zn deficiency, deleting the last 20 amino acids from the last transmembrane domain of TdZIP1 and tagging with GFP resulted in ER localization. Functional expression of the isolated TdZIP1 using Zn-uptake defective Saccharomyces cerevisiae strains on limiting Zn media showed that it could indeed transport Zn. However, overexpression of this transporter causes excess accumulation of Zn in the cells, thus generating a toxic environment. Overall, our results indicate the possibility of using T. dicoccoides for the genetic improvement of zinc efficiency in wheat.