The two copies of the zinc and cadmium ZIP6 transporter of Arabidopsis halleri have distinct effects on cadmium tolerance.

Julien Spielmann,Patrick Motte,Maxime Scheepers,Michael Weber,Stephan Clemens,Bernard Bosman,Hassan Ahmadi,Sarah Nitsche,Monique Carnol,Marc Hanikenne,Juergen Kroymann

doi:10.1111/pce.13806

Julien Spielmann, Patrick Motte + Show 9 more

Open Access

https://doi.org/10.1111/pce.13806

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Abstract

Plants have the ability to colonize highly diverse environments. The zinc and cadmium hyperaccumulator Arabidopsis halleri has adapted to establish populations on soils covering an extreme range of metal availabilities. The A. halleri ZIP6 gene presents several hallmarks of hyperaccumulation candidate genes: it is constitutively highly expressed in roots and shoots and is associated with a zinc accumulation quantitative trait locus. Here, we show that AhZIP6 is duplicated in the A. halleri genome. The two copies are expressed mainly in the vasculature in both A. halleri and Arabidopsis thaliana, indicative of conserved cis regulation, and acquired partial organ specialization. Yeast complementation assays determined that AhZIP6 is a zinc and cadmium transporter. AhZIP6 silencing in A. halleri or expression in A. thaliana alters cadmium tolerance, but has no impact on zinc and cadmium accumulation. AhZIP6-silenced plants display reduced cadmium uptake upon short-term exposure, adding AhZIP6 to the limited number of Cd transporters supported by in planta evidence. Altogether, our data suggest that AhZIP6 is key to fine-tune metal homeostasis in specific cell types. This study additionally highlights the distinct fates of duplicated genes in A. halleri.

Highlights

All organisms have to maintain adequate metal ion homeostasis to ensure growth and development in varying environments
Using ZIP6 RNAi A. halleri lines and A. thaliana transgenic plants overexpressing A. halleri ZIP6 (AhZIP6), we demonstrated that AhZIP6 alters cadmium tolerance
In spite of their long suspected importance for zinc acquisition and other aspects of zinc homeostasis, very little is known about the physiological roles of ZIP transporters (Ricachenevsky et al, 2015)

Summary

| INTRODUCTION

All organisms have to maintain adequate metal ion homeostasis to ensure growth and development in varying environments. Among uncharacterized candidate genes is ZIP6 (ZRT-IRT-like PROTEIN 6) It is 9- and 24-fold more highly expressed in roots and shoots of A. halleri compared with A. thaliana, respectively (Becher, Talke, Krall, & Krämer, 2004; Talke, Hanikenne, & Krämer, 2006) and is associated with a QTL for zinc accumulation in the presence of cadmium (Willems et al, 2010). It may be present in multiple copies in the A. halleri genome (Suryawanshi et al, 2016; Talke et al, 2006). Using ZIP6 RNAi A. halleri lines and A. thaliana transgenic plants overexpressing AhZIP6, we demonstrated that AhZIP6 alters cadmium tolerance

| RESULTS

| DISCUSSION

Findings

| METHODS