Arabidopsis Yellow Stripe-Like2 (YSL2): a metal-regulated gene encoding a plasma membrane transporter of nicotianamine-metal complexes.

The Yellow Stripe-Like (YSL) family of proteins has been identified based on sequence similarity to maize Yellow Stripe1 (YS1), the transporter responsible for the primary uptake of iron from the soil. YS1 transports iron that is complexed by specific plant-derived Fe(III) chelators called phytosiderophores (PS). Non-grass species of plants neither make nor use PS, yet YSL family members are found in non-grass species (monocot, dicot, gymnosperm, and moss species) including Arabidopsis thaliana. YSLs in non-grasses have been hypothesized to transport metals complexed by nicotianamine (NA), an iron chelator that is structurally similar to PS and which is found in all higher plants. Here we show that Arabidopsis YSL2 (At5g24380) transports iron and copper when these metals are chelated by NA. YSL2 is expressed in many cell types in both roots and shoots, suggesting that diverse cell types obtain metals as metal-NA complexes. YSL2 transcription is regulated by the levels of iron and copper in the growth medium. Based on its expression pattern, a major function of the YSL2 appears to be in the lateral movement of metals in the vasculature.