A specific transporter for iron(III)–phytosiderophore in barley roots

• Published in: The Plant journal : for cell and molecular biology Vol. 46; no. 4; pp. 563 - 572
• Main Authors: Murata, Yoshiko, Ma, Jian Feng, Yamaji, Naoki, Ueno, Daisei, Nomoto, Kyosuke, Iwashita, Takashi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.05.2006; Blackwell Science
• Subjects: Amino Acid Sequence; Amino acids; Animals; Biological and medical sciences; Botany; Cell physiology; epidermal cells of barley roots; Ferric Compounds - metabolism; Flowers & plants; Fundamental and applied biological sciences. Psychology; Genes; Hordeum - cytology; Hordeum - metabolism; iron(III)–phytosiderophore transporter; Iron-Binding Proteins - metabolism; Membrane Transport Proteins - analysis; Membrane Transport Proteins - chemistry; Membrane Transport Proteins - physiology; Molecular Sequence Data; mugineic acid; nicotianamine; Phylogeny; Plant physiology and development; Plant Proteins - analysis; Plant Proteins - chemistry; Plant Proteins - physiology; Plant Roots - metabolism; Plasma membrane and permeation; Protein Structure, Tertiary; Proteins; RNA, Messenger - metabolism; Sequence Alignment; tolerance of iron deficiency; Xenopus; YS1 gene; YS1 gene; Monocotyledones; Zea mays; Hordeum vulgare; Root; Secretion; nicotianamine; mugineic acid; Hybridization; tolerance of iron deficiency; epidermal cells of barley roots; Phytosiderophore; Gene; Gramineae; Aminoacid; Substrate specificity; Angiospermae; Spermatophyta; iron(III)-phytosiderophore transporter
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.02714.x

Summary 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.