Poster: Mineral nutrition

Abs # 207: Arabidopsis Yellow Stripe-Like genes encode membrane transporters of nicotianamine-metal complexes.

Presenter:	Walker, Elsbeth Lewis, ewalker@bio.umass.edu
Authors	Walker, Elsbeth Lewis (A)   Roberts, Louis A (A)   DiDonato, Raymond J (A)   Sanderson, Tamara  (A)
Affiliations:	(A): University Of Massachusetts

The regulation of metal distribution within plants is a complex and relatively poorly understood process. The YELLOW STRIPE-LIKE (YSL) proteins function as membrane bound transporters of iron and other transition metals. The YSLs were identified based on sequence similarity to YELLOW STRIPE1 (YS1), the transporter that, in maize, is responsible for primary uptake of iron from the soil. YS1 transports iron that is complexed by specific plant-derived Fe(III) chelators called phytosiderophores. Non-grass species of plants neither make nor use phytosiderophores, yet YSL family members are found in non-grass species (monocot, dicot, gymnosperm, and moss species) including Arabidopsis thaliana. Here we will present evidence that Arabidopsis YSL proteins transport iron and copper when these metals are chelated by nicotianamine (NA). Nicotianamine is a strong complexor of various transition metals, particularly Fe(II), and NA is found in all higher plants examined. YSL genes are expressed in many cell types in both roots and shoots, suggesting that diverse cell types obtain metals as metal-nicotianamine complexes. We will further focus on the YSL2 gene, whose transcription is regulated by the levels of iron and copper in the growth medium. YSL2 has an unusual pattern of distribution within the plasma membranes of vascular parenchyma cells that is consistent with a function in moving metals laterally within veins. Based on its expression pattern, the major function of YSL2 seems to be in lateral movement of metals within the vasculature. This movement appears to be most critical when iron is abundantly available, since YSL2 expression under iron-deficient growth conditions is reduced.