title: Silicon enhances leaf remobilization of iron in cucumber under limited iron conditions.
abstract: Retranslocation of iron (Fe) from source tissues enhances plant tolerance to Fe deficiency. Previous work has shown that silicon (Si) can alleviate Fe deficiency by enhancing acquisition and root to shoot translocation of Fe. Here the role of Si in Fe mobilization in older leaves and the subsequent retranslocation of Fe to young leaves of cucumber (Cucumis sativus) plants growing under Fe-limiting conditions was investigated.
  
  
  
  Iron ((57)Fe or naturally occurring isotopes) was measured in leaves at different positions on plants hydroponically growing with or without Si supply. In parallel, the concentration of the Fe chelator nicotianamine (NA) along with the expression of nicotianamine synthase (NAS) involved in its biosynthesis and the expression of yellow stripe-like (YSL) transcripts mediating Fe-NA transport were also determined.
  
  
  
  In plants not receiving Si, approximately half of the total Fe content remained in the oldest leaf. In contrast, Si-treated plants showed an almost even Fe distribution among leaves with four different developmental stages, thus providing evidence of enhanced Fe remobilization from source leaves. This Si-stimulated Fe export was paralleled by an increased NA accumulation and expression of the YSL1 transporter for phloem loading/unloading of the Fe-NA complex.
  
  
  
  The results suggest that Si enhances remobilization of Fe from older to younger leaves by a more efficient NA-mediated Fe transport via the phloem. In addition, from this and previous work, a model is proposed of how Si acts to improve Fe homeostasis under Fe deficiency in cucumber.
authors.affiliation: Plant Nutrition Research Group, Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11030 Belgrade, Serbia.
authors.forename: Jelena
authors.initials: J
authors.lastname: Pavlovic
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444-A, 11010 Belgrade, Serbia.
authors.forename: Jelena
authors.initials: J
authors.lastname: Samardzic
authors.affiliation: Plant Nutrition Research Group, Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11030 Belgrade, Serbia.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Kostic
authors.affiliation: Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: Kristian H
authors.initials: KH
authors.lastname: Laursen
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia.
authors.forename: Maja
authors.initials: M
authors.lastname: Natic
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444-A, 11010 Belgrade, Serbia.
authors.forename: Gordana
authors.initials: G
authors.lastname: Timotijevic
authors.affiliation: Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.affiliation: Plant Nutrition Research Group, Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11030 Belgrade, Serbia mnikolic@imsi.bg.ac.rs.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Nikolic
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D001383:Azetidinecarboxylic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001692:Biological Transport; D018553:Cucumis sativus / Q000187:drug effects* / Q000378:metabolism; D006706:Homeostasis; D018527:Hydroponics; D000090463:Iron Deficiencies; D008954:Models, Biological; D052585:Phloem / Q000187:drug effects / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012825:Silicon / Q000494:pharmacology*
chemical_list: D010940:Plant Proteins; C082893:nicotianamine; D001383:Azetidinecarboxylic Acid; D019883:Alkyl and Aryl Transferases; C118230:nicotianamine synthase; D012825:Silicon
keywords: Cucumber (Cucumis sativus); iron retranslocation; leaves; nicotianamine; nicotianamine synthase (NAS); phloem transport; silicon; yellow stripe-like (YSL) transporters