Abstract

Micronutrients such as zinc (Zn) and iron (Fe) are essential for normal plant growth but are toxic to cells when present in excess. Therefore, metal homeostasis networks exist to ensure optimal concentration of these elements while maintaining the availability of the free ions below toxicity thresholds. This involves coordinated regulation of metal transport proteins and chelating molecules. To identify regulatory mechanisms of metal homeostasis in plants, a forward genetic screen was used to identify mutations that disrupt up-regulation of ZINC -INDUCED FACILITATOR1 (ZIF1), a vacuolar nicotianamine transporter, by Zn. Several novel mutants were identified, including de-etiolated by Zn (dez) which has a photomorphogenic phenotype when grown in the dark on media containing high Zn. Phenotypic and microarray analysis implicated phytohormones and indicates that regulation of metal homeostasis is important for skotomorphogensis.