Integrating Iron Sensing and Iron Deficiency Signaling in Plants

Dartmouth College, Hanover NH

Investigators

Abstract

Iron often limits plant growth and agricultural yield. Furthermore, more than 2 billion people are iron deficient because their plant-based diets are not a rich source of iron, making iron deficiency the most prevalent nutritional problem in the world today. Clearly, understanding iron metabolism in plants is crucial, both from the point of view of improving plant growth and crop yields as well as improving human nutrition. Despite progress in tracing how iron moves throughout the plant, scientists still do not understand how plants sense and respond to iron availability. This project will help to explain how a protein called URI receives and then conveys information about the iron status of a cell. Such information should transform efforts towards sustainable improvements of crop yields in terms of plant productivity and plant nutrient content. In partnership with the Alan Alda Center for Communicating Science at Stony Brook University, workshops will be offered to train scientists to communicate more effectively with broad audiences: Improvisation for Scientists, Distilling your Message and Science Writing. Such training is, of course, important for all scientists but it is especially important for scientists who work in the area of genetically modified foods. Iron is an essential nutrient for plants. It functions to accept and donate electrons and plays important roles in the electron transport chains of photosynthesis and respiration. Although the mechanisms controlling iron uptake from the soil are relatively well understood, little is known about iron deficiency signaling in plants. The proposed research will build upon PI's isolation of a mutant, upstream regulator of IRT1 (uri), that no longer shows induction of most of the iron-regulated genes in the root. The causal mutation maps to the coding region of a bHLH transcription factor that itself is not transcriptionally regulated by iron availability. Experiments have been designed to test hypotheses on how changes in URI's phosphorylation state, stability and/or localization convey information about changes in iron status. Phosphorylated residues will be identified via mass spectrometry and phosphomimics will be constructed to confirm which residues are important for URI activity. Protein half -life will be assessed using transgenic plants expressing a URI-GFP fusion protein. These plants will also be used to determine whether URI undergoes nucleocytoplasmic shuffling in response to changes in iron levels. The fourth set of experiments address the hypothesis that URI binds iron directly and this alters its activity/stability and/or localization. The long-term goal is to understand the entire network of genes responsible for integrating information about iron status and orchestrating a coordinated response. The improvement of plant iron nutrition will deliver plants better able to grow in soils now considered marginal and will increase crop biomass on soils now in cultivation. Importantly, the production of iron-rich seed should lead to agronomic benefits such as increased seedling vigor, resistance to disease and other stresses and increased crop yields, while also addressing an important problem in human health by providing iron-rich foods.