title: Long-distance signals positively regulate the expression of iron uptake genes in tobacco roots.
abstract: Long-distance signals generated in shoots are thought to be associated with the regulation of iron uptake from roots; however, the signaling mechanism is still unknown. To elucidate whether the signal regulates iron uptake genes in roots positively or negatively, we analyzed the expressions of two representative iron uptake genes: NtIRT1 and NtFRO1 in tobacco (Nicotiana tabacum L.) roots, after shoots were manipulated in vitro. When iron-deficient leaves were treated with Fe(II)-EDTA, the expressions of both genes were significantly reduced; nevertheless iron concentration in the roots maintained a similar level to that in roots grown under iron-deficient conditions. Next, all leaves from tobacco plants grown under the iron-deficient condition were excised. The expression of two genes were quickly reduced below half within 2 h after the leaf excision and gradually disappeared by the end of a 24-h period. The NtIRT1 expression was compared among the plants whose leaves were cut off in various patterns. The expression increased in proportion to the dry weight of iron-deficient leaves, although no relation was observed between the gene expression and the position of excised leaves. Interestingly, the NtIRT1 expression in hairy roots increased under the iron-deficient condition, suggesting that roots also have the signaling mechanism of iron status as well as shoots. Taken together, these results indicate that the long-distance signal generated in iron-deficient tissues including roots is a major factor in positive regulation of the expression of NtIRT1 and NtFRO1 in roots, and that the strength of the signal depends on the size of plants.
authors.affiliation: Biotechnology Sector, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-Shi, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Enomoto
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Hodoshima
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shimada
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shoji
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yoshihara
authors.forename: Fumiyuki
authors.initials: F
authors.lastname: Goto
mesh_terms: D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D004492:Edetic Acid / Q000494:pharmacology; D005296:Ferrous Compounds / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D007501:Iron / Q000378:metabolism*; D008954:Models, Biological; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism
chemical_list: D005296:Ferrous Compounds; D010940:Plant Proteins; C055526:Fe(II)-EDTA; D013395:Sucrose; D004492:Edetic Acid; D007501:Iron