title: Cytochrome b5 Reductase 1 Triggers Serial Reactions that Lead to Iron Uptake in Plants.
abstract: Rhizosphere acidification is essential for iron (Fe) uptake into plant roots. Plasma membrane (PM) H(+)-ATPases play key roles in rhizosphere acidification. However, it is not fully understood how PM H(+)-ATPase activity is regulated to enhance root Fe uptake under Fe-deficient conditions. Here, we present evidence that cytochrome b5 reductase 1 (CBR1) increases the levels of unsaturated fatty acids, which stimulate PM H(+)-ATPase activity and thus lead to rhizosphere acidification. CBR1-overexpressing (CBR1-OX) Arabidopsis thaliana plants had higher levels of unsaturated fatty acids (18:2 and 18:3), higher PM H(+)-ATPase activity, and lower rhizosphere pH than wild-type plants. By contrast, cbr1 loss-of-function mutant plants showed lower levels of unsaturated fatty acids and lower PM H(+)-ATPase activity but higher rhizosphere pH. Reduced PM H(+)-ATPase activity in cbr1 could be restored in vitro by addition of unsaturated fatty acids. Transcript levels of CBR1, fatty acids desaturase2 (FAD2), and fatty acids desaturase3 (FAD3) were increased under Fe-deficient conditions. We propose that CBR1 has a crucial role in increasing the levels of unsaturated fatty acids, which activate the PM H(+)-ATPase and thus reduce rhizosphere pH. This reaction cascade ultimately promotes root Fe uptake.
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Oh
authors.affiliation: Department Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Hanul
authors.initials: H
authors.lastname: Kim
authors.affiliation: Division of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Sung Hee
authors.initials: SH
authors.lastname: Seo
authors.affiliation: Division of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Bae Geun
authors.initials: BG
authors.lastname: Hwang
authors.affiliation: Division of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Yoon Seok
authors.initials: YS
authors.lastname: Chang
authors.affiliation: Department Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Junho
authors.initials: J
authors.lastname: Lee
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Lee
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Sohn
authors.affiliation: Division of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Sang Joon
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea; Department Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea; Department Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea. Electronic address: ihhwang@postech.ac.kr.
authors.forename: Inhwan
authors.initials: I
authors.lastname: Hwang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D042966:Cytochrome-B(5) Reductase / Q000235:genetics / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007501:Iron / Q000378:metabolism*; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000378:metabolism; D058441:Rhizosphere; D012639:Seeds / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D012995:Solubility; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D005231:Fatty Acids, Unsaturated; D012987:Soil; D007501:Iron; C587934:CBR1 protein, Arabidopsis; D042966:Cytochrome-B(5) Reductase; D006180:Proton-Translocating ATPases
keywords: H(+)-ATPase; cytochrome b5 reductase 1 (CBR1); iron (Fe) uptake; unsaturated fatty acids