Sisó-Terraza Patricia, Rios Juan J, Abadía Javier, Abadía Anunciación, Álvarez-Fernández Ana
Department of Plant Nutrition, Estación Experimental de Aula Dei (CSIC), Av. Montañana 1005, E-50080, Zaragoza, Spain.
New Phytol. 2016 Jan;209(2):733-45. doi: 10.1111/nph.13633. Epub 2015 Sep 9.
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.
铁(Fe)在土壤中含量丰富,但通常溶解度很低。除禾本科植物外,植物通过与铁(II)转运蛋白偶联的铁(III)螯合物还原酶来吸收铁。到目前为止,非禾本科物种是否能将难溶性的铁(III)形式转化为可溶性铁形式几乎没有受到关注。我们使用了甜菜(Beta vulgaris),它是许多在缺铁时根部会分泌黄素的物种之一,来研究黄素是否参与铁的获取。从营养液中去除缺铁植物分泌的黄素,并将这些植物与铁充足的植物以及未去除黄素的缺铁植物进行比较。在有或没有黄素、烟酰胺腺嘌呤二核苷酸还原形式(NADH)、植物根系以及一种铁(II)捕获剂的情况下,评估一种难溶性铁(III)氧化物的溶解情况。从营养液中去除黄素会加重缺铁诱导的叶片黄化。在有NADH存在的情况下,黄素能够溶解铁(III)氧化物。添加细胞外黄素能使缺铁植物的根系还原性地溶解铁(III)氧化物。我们得出结论,黄素的根系分泌改善了甜菜的铁营养状况。黄素使甜菜根系能够通过还原机制从铁(III)氧化物中获取铁。