NtZIP11, a new Zn transporter specifically upregulated in tobacco leaves by toxic Zn level

Abstract

Understanding the molecular mechanisms governing the uptake and accumulation of Zn in the leaves of tobacco plants exposed to high Zn concentrations is important from the perspective of phytoremediation of metal contaminated soil. This study identifies a new candidate gene, NtZIP11, which may contribute to Zn accumulation in tobacco leaves. NtZIP11 encodes a protein of 346 amino acids, with characteristic conserved sequences of the ZIP family of proteins. Phylogenetic analysis shows that NtZIP11 forms a distinct clade with other ZIP11 proteins. Transient expression of GFP-tagged ZIP11 in the abaxial epidermis of tobacco leaves demonstrates localization at the plasma membrane. Yeast complementation tests and growth assays indicate that NtZIP11 is involved in Zn but not Fe, Mn and Cd uptake. NtZIP11 complements the zrt1zrt2 mutant deficient in Zn uptake, but not the fet3fet4 mutant deficient in Fe uptake. Nor does it modify the sensitivity of wild-type yeast, DY1457, to increasing concentrations of Fe, Mn and Cd. NtZIP11 is expressed in both roots and leaves, with transcript abundance increasing with age. Noteworthy, the expression level of NtZIP11 is not modulated by Zndeficiency but is highly upregulated especially in the older leaves by high Zn concentrations (50 and 200 µM). Our data indicate that the primary role for NtZIP11 is in the uptake of Zn by the cells of tobacco leaves specifically when experiencing high Zn concentrations. It also likely contributes to maintaining a basal supply of Zn to cells at the level of the whole plant. Thus the present study contributes to broadening our understanding of Zn homeostasis mechanisms in tobacco, and clarifying the role of ZIP11 genes.

Dual Role of Metallic Trace Elements in Stress Biology—From Negative to Beneficial Impact on Plants

“…In this case, several other classes of metal transporters that are located in both plasma membrane and tonoplast play a pivotal role in regulating the metal content within the protoplasts. Among them, heavy metal transporting ATPases (HMA), the natural resistance-associated macrophage proteins (Nramp), the cation exchangers (CAXs), the cation diffusion facilitator (CDF), or ZIP family transporters could be mentioned [28,29,30].…”

Heterologous expression of the human ZIP4 zinc transporter in Saccharomyces cerevisiae

“…Deletion of the two ZIP genes, zrt1 and zrt2, in S. cerevisiae, produces a growth phenotype sensitive to zinc-limited conditions. Thus, functional expression of hZIP4 in the zrt1/zrt2 deletion strain S. cerevisiae ZHY3 was expected to restore its zinc-dependent growth rate, as has been shown for a number of plant and fungal ZIP homologues that have been expressed in ZHY3 [27][28][29] . Surprisingly, growth of ZHY3 expressing either full-length hZIP4 or the hZIP4 membrane domain was repressed further in zinc-limited growth conditions.…”

Potential ability of tobacco (Nicotiana tabacum L.) to phytomanage an urban brownfield soil

“…At the Lommel site, Belgium (sandy soil, soil pH 6.4–6.8), the shoot concentrations of BaG tobacco reached 250–475 mg Zn and 10–27 mg Cd kg −1 DW, Cd being more uptake than at the Borifer site (Thijs et al 2018 ). Some papers reported on the root-to-shoot translocation of Zn and Cd in tobacco and Zrt-/Irt-like proteins (ZIPs), which carry Zn from extracellular space and intracellular compartments to the cytosol (Kozak et al 2019 ). High Zn and Cd exposures induced changes in root part-specific expression pattern of such membrane transporters, i.e., NtZIP1-like , NtZIP5-like , NtZIP8 , NtZIP11 , NtIRT1 , and NtIRT1-like (Palusińska et al, 2020 ).…”

“…High Zn and Cd exposures induced changes in root part-specific expression pattern of such membrane transporters, i.e., NtZIP1-like , NtZIP5-like , NtZIP8 , NtZIP11 , NtIRT1 , and NtIRT1-like (Palusińska et al, 2020 ). The NtZIP11 plasma membrane protein, being highly expressed in tobacco leaves and upregulated by high Zn concentrations (Kozak et al 2019 ), may contribute to accumulate Zn in leaves in conditions of Zn excess as in the case of B soil. With high Zn exposure in hydroponic, Zn-containing biogenic calcite and other Zn compounds are produced through the tobacco trichomes, and this would be a mechanism involved in Zn detoxification (Sarret et al 2006 ).…”