Mobilization of Iron by Plant-Borne Coumarins

• Published in: Trends in plant science Vol. 22; no. 6; pp. 538 - 548
• Main Authors: Tsai, Huei Hsuan, Schmidt, Wolfgang
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2017; Elsevier BV
• Subjects: Alkaline soils; Biosynthesis; Chelation; coumarins; Coumarins - metabolism; crops; Flowers & plants; Iron; Iron - deficiency; Iron - metabolism; Iron and steel making; pH effects; phenolics; phenylpropanoid pathway; Plant communities; Plant Exudates - metabolism; Plant Roots - metabolism; Plants (botany); Rhizosphere; root exudates; solubility; iron deficiency; phenylpropanoid pathway; root exudates; phenolics; rhizosphere
• ISSN: 1360-1385; 1878-4372; 1878-4372
• DOI: 10.1016/j.tplants.2017.03.008

Iron is one of the most abundant elements in soils, but its low phytoavailability at high pH restricts plant communities on alkaline soils to taxa that have evolved efficient strategies to increase iron solubility. Recent evidence provides support for a previously underestimated role of root-secreted coumarins in mobilizing iron through reduction and chelation as part of an orchestrated strategy evolved to improve the acquisition of iron from recalcitrant pools. Understanding the mechanisms that tune the production of iron-mobilizing coumarins and their intricate interplay with other biosynthesis pathways could yield clues for deciphering the molecular basis of ‘iron efficiency’ – the ability of plants to thrive on soils with limited iron availability – and may open avenues for generating iron-fortified crops. Recent studies have uncovered a crucial role of secreted coumarins in the acquisition of iron, particularly under alkaline conditions. The importance of coumarins in iron acquisition has been widely underestimated in previous studies that have typically been carried out under acidic conditions, thereby masking the role of coumarins. The efficiency of coumarin-aided mobilization of iron from recalcitrant iron pools may have important consequences for the structure of natural ecosystems, and could be a limiting factor for the yield and nutritional quality of crops grown on alkaline soils. Iron deficiency-induced coumarin biosynthesis is subject to sophisticated regulation and is interlinked with other biosynthesis and signaling pathways to allow an orchestrated response to developmental and environmental cues.