Intron retention in the 5'UTR of the novel ZIF2 transporter enhances translation to promote zinc tolerance in arabidopsis

PLoS Genet. 2014 May 15;10(5):e1004375. doi: 10.1371/journal.pgen.1004375. eCollection 2014.

Abstract

Root vacuolar sequestration is one of the best-conserved plant strategies to cope with heavy metal toxicity. Here we report that zinc (Zn) tolerance in Arabidopsis requires the action of a novel Major Facilitator Superfamily (MFS) transporter. We show that ZIF2 (Zinc-Induced Facilitator 2) localises primarily at the tonoplast of root cortical cells and is a functional transporter able to mediate Zn efflux when heterologously expressed in yeast. By affecting plant tissue partitioning of the metal ion, loss of ZIF2 function exacerbates plant sensitivity to excess Zn, while its overexpression enhances Zn tolerance. The ZIF2 gene is Zn-induced and an intron retention event in its 5'UTR generates two splice variants (ZIF2.1 and ZIF2.2) encoding the same protein. Importantly, high Zn favours production of the longer ZIF2.2 transcript, which compared to ZIF2.1 confers greater Zn tolerance to transgenic plants by promoting higher root Zn immobilization. We show that the retained intron in the ZIF2 5'UTR enhances translation in a Zn-responsive manner, markedly promoting ZIF2 protein expression under excess Zn. Moreover, Zn regulation of translation driven by the ZIF2.2 5'UTR depends largely on a predicted stable stem loop immediately upstream of the start codon that is lost in the ZIF2.1 5'UTR. Collectively, our findings indicate that alternative splicing controls the levels of a Zn-responsive mRNA variant of the ZIF2 transporter to enhance plant tolerance to the metal ion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions / genetics
  • Arabidopsis / drug effects
  • Arabidopsis / genetics*
  • Gene Expression Regulation, Plant / drug effects
  • Heavy Metal Poisoning*
  • Homeostasis
  • Introns / genetics*
  • Plant Roots / genetics
  • Plant Roots / growth & development
  • Plants, Genetically Modified / genetics
  • Poisoning / genetics*
  • RNA, Messenger / biosynthesis
  • Vacuoles / metabolism
  • Zinc / toxicity*

Substances

  • 5' Untranslated Regions
  • RNA, Messenger
  • Zinc

Grant support

This work was funded by Fundação para a Ciência e a Tecnologia (http://www.fct.pt/index.phtml.pt): Grant PTDC/AGR-AAM/102967/2008 awarded to PD as well as PostDoctoral Fellowships SFRH/BPD/44640/2008 and SFRH/BPD/81221/2011 awarded to ER and TRC, respectively. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.