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First published online August 3, 2007; 10.1105/tpc.106.049015 The Plant Cell 19:2624-2635 (2007) © 2007 American Society of Plant Biologists 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
a Biotechnology Research Center, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan 2 Address correspondence to atorufu{at}mail.ecc.u-tokyo.ac.jp.
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–ß-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. This article has been cited by other articles:
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