Structural and Functional Characterization of AvsYS1: A Phytosiderophore – Ferric Iron Transport Protein

Over 820 million people are hungry every day around the world. Due to pH issues in the soil, plants cannot acquire their nutrients to survive. One of the rate-limiting micronutrients in plant growth is iron (Fe). Fe is an essential element needed for both humans and plants to survive. Humans suffer from iron deficiency anemia (IDA), which effects over 2 billion people worldwide, and is defined by the inability of red blood cells to transport oxygen. Plants, however, suffer from iron deficiency chlorosis (IDC), which is characterized by the yellowing of leaves due to decreased chlorophyll content, and mobilization of iron. To acquire Fe, plants use two different strategies. Graminaceous plants (grasses) take up iron by secreting iron-chelating agents known as phytosiderophore (PS). Once chelated, yellow stripe 1 (YS1) and YS1-like (YSL) transporters transport the Fe3+ - PS complex into the root. Since 2001, multiple YS1 and YSL transporters have been identified and characterized beyond sequence analysis. In 2008, Tomcavage and Davis isolated a putative YS1 transporter from Avena sativa (oats) designated AvsYS1. The cDNA was isolated but AvsYS1 was never characterized. Using phylogenetic analysis, a liquid yeast complementation assay, and densitometry, AvsYS1 gene and protein were structurally and functionally confirmed as a YS1 transporter.