A specific transporter for iron(III)-phytosiderophore in barley roots.
Iron acquisition of graminaceous plants is characterized by the synthesis and secretion of the iron-chelating phytosiderophore, mugineic acid (MA), and by a specific uptake system for iron(III)-phytosiderophore complexes. We identified a gene specifically encoding an iron-phytosiderophore transporter (HvYS1) in barley, which is the most tolerant species to iron deficiency among graminaceous plants. HvYS1 was predicted to encode a polypeptide of 678 amino acids and to have 72.7% identity with ZmYS1, a first protein identified as an iron(III)-phytosiderophore transporter in maize. Real-time RT-PCR analysis showed that the HvYS1 gene was mainly expressed in the roots, and its expression was enhanced under iron deficiency. In situ hybridization analysis of iron-deficient barley roots revealed that the mRNA of HvYS1 was localized in epidermal root cells. Furthermore, immunohistological staining with anti-HvYS1 polyclonal antibody showed the same localization as the mRNA. HvYS1 functionally complemented yeast strains defective in iron uptake on media containing iron(III)-MA, but not iron-nicotianamine (NA). Expression of HvYS1 in Xenopus oocytes showed strict specificity for both metals and ligands: HvYS1 transports only iron(III) chelated with phytosiderophore. The localization and substrate specificity of HvYS1 is different from those of ZmYS1, indicating that HvYS1 is a specific transporter for iron(III)-phytosiderophore involved in primary iron acquisition from soil in barley roots.
Murata
Yoshiko
Y
Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan. murata@sunbor.or.jp
Ma
Jian Feng
JF
Yamaji
Naoki
N
Ueno
Daisei
D
Nomoto
Kyosuke
K
Iwashita
Takashi
T
D000595:Amino Acid Sequence; D000818:Animals; D005290:Ferric Compounds / Q000378:metabolism*; D001467:Hordeum / Q000166:cytology / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D016415:Sequence Alignment; D014981:Xenopus
D005290:Ferric Compounds; D033862:Iron-Binding Proteins; D026901:Membrane Transport Proteins; D010940:Plant Proteins; D012333:RNA, Messenger