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　　Iron is an essential mineral nutrient which severely affects the growth, yield, and nutritional quality of plants if not supplied in sufficient quantities. However, how plants integrate the demand of different plant parts and regulate the amount of iron taken up by roots remains largely unknown.

　　A team led by Dr. Wolfgang Schmidt, a Research Fellow in the Institute of Plant and Microbial Biology at Academia Sinica, has identified a new family of small peptides named IRON MAN (IMA) that regulate iron homeostasis by acting as phloem-mobile signals in flowering plants. Genes encoding IMA peptides are present in the genomes of all flowering plants but are missing in ferns, algae or fungi, suggesting that these genes emerged at an early stage in the evolution of land plants. Despite their ubiquitous presence, IMA peptides have not been recognized as a family due to their highly variable sizes and structures, and their corresponding genes have remained largely undocumented.

　　Although highly diverse across species, all IRON MAN peptides contain a conserved consensus motif and the deletion of which abolishes their function. The genome of the model plant Arabidopsis thaliana contains eight genes encoding IMA peptides with partly redundant function. Silencing of all IMA genes by CRISPR-Cas9 genome editing resulted in very small, extremely chlorotic (i.e. iron undernourished) plants that died when not supplemented with high amounts of external iron. Reciprocal grafting of ima mutants and wild-type plants showed that IMA peptides in shoots positively regulate iron uptake in roots, suggesting that IMAs are the long sought-after shoot-borne signal that communicates the iron status of the leaves to tune iron uptake by roots. The results were published in Nature Plants on October 10, 2018.

　　Insufficient dietary iron intake resulting from low iron concentrations in edible plant parts is the cause of iron deficiency-induced anemia, affecting more than one billion people worldwide, particularly in areas where iron supply depends mainly or entirely on plants. Increasing the abundance of IMA peptides in plants was found to increase the iron content not only in Arabidopsis seeds but also in edible parts of crops such as tomato fruits, opening a novel route for generating iron-enriched plants that may aid in combating iron deficiency-induced anemia.

Full Article: https://www.nature.com/articles/s41477-018-0266-y



Image: Visualization of iron by Perls’–DAB staining in cross-sections of stems from wild-type (cv. Microtom) and AtIMA1c Ox plants; scale bars, 100 µm.