title: Early senescence of the oldest leaves of Fe-deficient barley plants may contribute to phytosiderophore release from the roots.
abstract: Barley (Hordeum vulgare), which tolerates iron (Fe) deficiency, secretes a large amount of phytosiderophores from its roots. However, how barley is able to allocate resources for phytosiderophore synthesis when the carbon assimilation rate is reduced by Fe deficiency is unknown. We previously suggested that the acceleration of senescence in older leaves triggered by Fe deficiency may allow the recycling of assimilates to contribute to phytosiderophore synthesis. In this work, we show the relationship between an increase in the C/N ratio in older leaves and Fe-deficiency tolerance among three barley cultivars. The increase in the C/N ratio suggests an enhanced capacity for the retranslocation of carbohydrates or amino acids from older leaves to the sink organs. An increase in the sucrose concentration in Fe-deficient barley also suggests active redistribution of assimilates. This metabolic modulation may be supported by accelerated senescence of older leaves, as Fe deficiency increased the expression of senescence-associated genes. The older leaves of Fe-deficient barley maintained CO2 assimilation under Fe deficiency. Barley that had been Fe-deficient for 3 days preferentially allocated newly assimilated (13) C to the roots and nutrient solution. Interestingly, the oldest leaf of Fe-deficient barley released more (13) C into the nutrient solution than the second oldest leaf. Thus, the balance between anabolism and catabolism in older leaves, supported by highly regulated senescence, plays a key role in metabolic adaptation in Fe-deficient barley.
authors.affiliation: Department of Applied Biology and Chemistry, Laboratory of Plant Production Chemistry, Tokyo University of Agriculture, Tokyo, 156-8502, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Higuchi
authors.forename: Jun
authors.initials: J
authors.lastname: Iwase
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Tsukiori
authors.forename: Daiki
authors.initials: D
authors.lastname: Nakura
authors.forename: Nahoko
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Hidenori
authors.initials: H
authors.lastname: Ohashi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Saito
authors.forename: Eitaro
authors.initials: E
authors.lastname: Miwa
mesh_terms: D000222:Adaptation, Physiological; D000596:Amino Acids / Q000378:metabolism; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D007501:Iron / Q000378:metabolism*; D000090463:Iron Deficiencies; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018517:Plant Roots / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017262:Siderophores / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism; D013997:Time Factors
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D017262:Siderophores; D002245:Carbon Dioxide; D013395:Sucrose; D002244:Carbon; D007501:Iron; D009584:Nitrogen