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.
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-beta-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.
Biotechnology Research Center, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Yuko
Y
Nakagawa
Hideki
H
Hanaoka
Masaharu
M
Kobayashi
Kazumaru
K
Miyoshi
Kyoko
K
Miwa
Toru
T
Fujiwara
D017920:Antiporters / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D001692:Biological Transport / Q000187:drug effects; D001895:Boron / Q000172:deficiency / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D009928:Organ Specificity / Q000187:drug effects; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects; D052584:Xylem / Q000187:drug effects / Q000378:metabolism*
D017920:Antiporters; D029681:Arabidopsis Proteins; C469216:BOR1 protein, Arabidopsis; D026901:Membrane Transport Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D001895:Boron