Cell-Type Specificity of the Expression of Os BOR1, a Rice Efflux Boron Transporter Gene, Is Regulated in Response to Boron Availability for Efficient Boron Uptake and Xylem Loading

• Published in: The Plant cell Vol. 19; no. 8; pp. 2624 - 2635
• Main Authors: Nakagawa, Yuko, Hanaoka, Hideki, Kobayashi, Masaharu, Miyoshi, Kazumaru, Miwa, Kyoko, Fujiwara, Toru
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01.08.2007
• Subjects: Antiporters - genetics; Arabidopsis Proteins - genetics; Biological Transport - drug effects; Boron; Boron - deficiency; Boron - metabolism; Boron - pharmacology; Cell Membrane - drug effects; Cell walls; Complementary DNA; Gene Expression Regulation, Plant - drug effects; Genes, Plant; Genetic Complementation Test; Membrane Transport Proteins - genetics; Models, Biological; Molecular Sequence Data; Mutagenesis, Insertional; Mutation; Organ Specificity - drug effects; Oryza - drug effects; Oryza - genetics; Oryza - growth & development; Oryza - metabolism; Oryza sativa; Phylogeny; Plant cells; Plant growth; Plant Proteins - genetics; Plant Proteins - metabolism; Plant roots; Plant Roots - cytology; Plant Roots - drug effects; Plant Roots - genetics; Plants; Promoter Regions, Genetic - genetics; Rice; RNA, Messenger - genetics; RNA, Messenger - metabolism; Roots; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - drug effects; Transgenic plants; Xylem; Xylem - drug effects; Xylem - metabolism
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.106.049015

We describe a boron (B) transporter, Os BOR1, in rice (Oryza sativa). Os BOR1 is a plasma membrane-localized efflux transporter of B and is required for normal growth of rice plants under conditions of limited B supply (referred to as -B). Disruption of Os BOR1 reduced B uptake and xylem loading of B. The accumulation of Os BOR1 transcripts was higher in roots than that in shoots and was not affected by B deprivation; however, Os BOR1 was detected in the roots of wild-type plants under -B conditions, but not under normal conditions, suggesting regulation of protein accumulation in response to B nutrition. Interestingly, tissue specificity of Os BOR1 expression is affected by B treatment. Transgenic rice plants containing an Os BOR1 promoter-β-glucuronidase (GUS) fusion construct grown with a normal B supply showed the strongest GUS activity in the steles, whereas after 3 d of -B treatment, GUS activity was elevated in the exodermis. After 6 d of -B treatment, GUS activity was again strong in the stele. Our results demonstrate that Os BOR1 is required both for efficient B uptake and for xylem loading of B. Possible roles of the temporal changes in tissue-specific patterns of Os BOR1 expression in response to B condition are discussed.