Suppression of NtZIP4A/B Changes Zn and Cd Root-to-Shoot Translocation in a Zn/Cd Status-Dependent Manner.

Karolina Maślińska-Gromadka,Małgorzata Palusińska,Danuta Maria Antosiewicz,Anna Barabasz,Katarzyna Kozak

doi:10.3390/ijms22105355

Karolina Maślińska-Gromadka, Małgorzata Palusińska + Show 3 more

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https://doi.org/10.3390/ijms22105355

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Abstract

In tobacco, the efficiency of Zn translocation to shoots depends on Zn/Cd status. Previous studies pointed to the specific contribution of root parts in the regulation of this process, as well as the role of NtZIP4A/B (from the ZIP family; Zrt Irt-like Proteins). Here, to verify this hypothesis, NtZIP4A/B RNAi lines were generated. Then, in plants exposed to combinations of Zn and Cd concentrations in the medium, the consequences of NtZIP4A/B suppression for the translocation of both metals were determined. Furthermore, the apical, middle, and basal root parts were examined for accumulation of both metals, for Zn localization (using Zinpyr-1), and for modifications of the expression pattern of ZIP genes. Our results confirmed the role of NtZIP4A/B in the control of Zn/Cd-status-dependent transfer of both metals to shoots. Furthermore, they indicated that the middle and basal root parts contributed to the regulation of this process by acting as a reservoir for excess Zn and Cd. Expression studies identified several candidate ZIP genes that interact with NtZIP4A/B in the root in regulating Zn and Cd translocation to the shoot, primarily NtZIP1-like in the basal root part and NtZIP2 in the middle one.

Highlights

The efficiency of zinc (Zn) root-to-shoot translocation is a key factor conditioning the supply of the shoot with this micronutrient needed for the proper development of the plant
Knowing that NtZIP4A and NtZIP4B are upregulated at Zn deficiency [31], to determine the degree of transcript reduction, tested RNA interference (RNAi) lines and WT plants were grown in Zn deficient conditions for four days and in the control medium
Knowing that suppression of NtZIP4A/B leads to Zn/Cd status-dependent reduction in Zn and Cd translocation (Figures 1 and 2), we examined if the distribution of Zn and Cd along the root was affected in the NtZIP4A/BRNAi plants

Summary

Introduction

The efficiency of zinc (Zn) root-to-shoot translocation is a key factor conditioning the supply of the shoot with this micronutrient needed for the proper development of the plant. In the presence of cadmium (Cd) and excess Zn in the environment, processes that regulate translocation may limit or increase delivery of these elements to the shoots, impacting the level of accumulation and, plant-derived food quality or a plant’s industrial use. Tobacco is known for high efficiency of Cd and Zn translocation to leaves, which, on one hand, is a danger to smokers [5], but on the other, is an advantage for its use to phytoremediate contaminated soils [6,7]. The mechanisms underlying root-to-shoot translocation of Zn and Cd (and other metals) are not well understood [8,9]. Two major factors are involved in the regulation of the efficiency of metal transfer to aerial plant parts

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