Involvement of the ABCG37 transporter in secretion of scopoletin and derivatives by Arabidopsis roots in response to iron deficiency

13 Págs., 6 Figs., 2 Tabls. Available online 10 September 2013. The definitive version is available at: http://onlinelibrary.wiley.com/doi/10.1111/nph.12471/abstractStudies of Iron (Fe) uptake mechanisms by plant roots have focussed on Fe(III)-siderophores or Fe(II) transport systems. Iron deficency also enhances root secretion of flavins and phenolics. However, the nature of these compounds, their transport outside the roots and their role in Fe nutrition are largely unknown. We used HPLC/ESI-MS (TOF) and HPLC/ESI-MS/MS (ion trap) to characterize fluorescent phenolic-type compounds accumulated in roots or exported to the culture medium of Arabidopsis plants in response to Fe deficiency. Wild-type and mutant plants altered either in phenylpropanoid biosynthesis or in the ABCG37 (PDR9) ABC transporter were grown under standard or Fe-deficient nutrition conditions and compared. Fe deficiency upregulates the expression of genes encoding enzymes of the phenylpropanoid pathway and leads to the synthesis and secretion of phenolic compounds belonging to the coumarin family. The ABCG37 gene is also upregulated in response to Fe deficiency and coumarin export is impaired in pdr9 mutant plants. Therefore it can be concluded that: Fe deficiency induces the secretion of coumarin compounds by Arabidopsis roots; the ABCG37 ABC transporter is required for this secretion to take place; and these compounds improved plant Fe nutrition.Work supported in the framework of the European Transnational Cooperation within the PLANT-KBBE Initiative funded by the Spanish Ministry of Economy and Competitivity (MINECO EUI2008-03618 to J.A.) and the Agence Nationale de la Recherche (ANR-08-KBBE-009-01 to J-F.B.), the Spanish MINECO Projects AGL2010-16515 and AGL2012-31988 (cofinanced with FEDER) and the Aragon Government (Group A03)Peer reviewe