Flavins secreted by roots of iron‐deficient Beta vulgaris enable mining of ferric oxide via reductive mechanisms

• Published in: The New phytologist Vol. 209; no. 2; pp. 733 - 745
• Main Authors: Sisó‐Terraza, Patricia, Rios, Juan J, Abadía, Javier, Abadía, Anunciación, Álvarez‐Fernández, Ana
• Format: Journal Article
• Language: English
• Published: England Academic Press 01.01.2016; New Phytologist Trust; Wiley Subscription Services, Inc
• Subjects: Adenine; Beta vulgaris; Beta vulgaris - drug effects; Beta vulgaris - metabolism; Chlorosis; dicotyledoneous plants; Extracellular; Ferric Compounds - metabolism; Ferric oxide; Flavin; flavins; Flavins - metabolism; Flavins - pharmacology; Iron; Iron - metabolism; Iron - pharmacokinetics; iron acquisition; Iron deficiency; iron nutrition; leaves; Metals - metabolism; Metals - pharmacokinetics; Mineral nutrients; NAD; NAD (coenzyme); NAD - metabolism; NADH; Nicotinamide; Nicotinamide adenine dinucleotide; nutrient deficiencies; Nutrient deficiency; nutrient solutions; Nutrition; Oxidation; Oxides; Plant Leaves - metabolism; Plant roots; Plant Roots - metabolism; redox shuttle; Reductases; Removal; root secretion; Roots; Secretion; Soil; Solubility; Solubilization; dicotyledoneous plants; redox shuttle; iron nutrition; flavins; iron deficiency; Beta vulgaris; iron acquisition; root secretion
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.13633

Iron (Fe) is abundant in soils but generally poorly soluble. Plants, with the exception of Graminaceae, take up Fe using an Fe(III)‐chelate reductase coupled to an Fe(II) transporter. Whether or not nongraminaceous species can convert scarcely soluble Fe(III) forms into soluble Fe forms has deserved little attention so far. We have used Beta vulgaris, one among the many species whose roots secrete flavins upon Fe deficiency, to study whether or not flavins are involved in Fe acquisition. Flavins secreted by Fe‐deficient plants were removed from the nutrient solution, and plants were compared with Fe‐sufficient plants and Fe‐deficient plants without flavin removal. Solubilization of a scarcely soluble Fe(III)‐oxide was assessed in the presence or absence of flavins, NADH (nicotinamide adenine dinucleotide, reduced form) or plant roots, and an Fe(II) trapping agent. The removal of flavins from the nutrient solution aggravated the Fe deficiency‐induced leaf chlorosis. Flavins were able to dissolve an Fe(III)‐oxide in the presence of NADH. The addition of extracellular flavins enabled roots of Fe‐deficient plants to reductively dissolve an Fe(III)‐oxide. We concluded that root‐secretion of flavins improves Fe nutrition in B. vulgaris. Flavins allow B. vulgaris roots to mine Fe from Fe(III)‐oxides via reductive mechanisms.