LKP1 (LOV kelch protein 1): a factor involved in the regulation of flowering time in Arabidopsis

Authors

  • Tomohiro Kiyosue,

    Corresponding author
    1. 1 Gene Research Center, Kagawa University, Miki-cho, Kita-gun, Kagawa 761–0795, Japan, 2 Biological Regulation Division, Department of Regulation Biology, National Institute for Basic Biology (NIBB), Okazaki 444–8585, Japan, and 3 Department of Biology, Faculty of Science, Tokyo Metropolitan University, Minami-ôsawa 1–1, Hachioji, Tokyo 192–0397, Japan
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  • and 1,2, Masamitsu Wada 2,3

    1. 1 Gene Research Center, Kagawa University, Miki-cho, Kita-gun, Kagawa 761–0795, Japan, 2 Biological Regulation Division, Department of Regulation Biology, National Institute for Basic Biology (NIBB), Okazaki 444–8585, Japan, and 3 Department of Biology, Faculty of Science, Tokyo Metropolitan University, Minami-ôsawa 1–1, Hachioji, Tokyo 192–0397, Japan
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*For correspondence (fax +81 878 91 3021; e-mail tkiyosue@ag.kagawa-u.ac.jp).

Summary

In plants, light is not only an energy source but also a very important signal that modulates development and differentiation. Here, we report a putative photo-regulatory factor sequence in LKP1 (LOV kelch protein 1). LKP1 cDNA encodes a protein of 610 amino acids and with a molecular weight of 65 905 with an LOV domain and kelch repeats. LOV domains are present in a number of sensor proteins involved in the detection of light, oxygen or voltage. The LKP1 LOV is very similar to the LOV domains in NPH1, a plasma membrane-associated blue light receptor kinase that regulates phototropism (Huala, E., Oeller, P.W., Liscum, E., Han, I-S., Larsen, E. & Briggs, W.R. (1997) Science, 278, 2120–2123). LKP1 mRNA accumulates in roots, stems, flowers and siliques. It is most abundant in leaves, and least abundant in seeds. Transgenic plants with a β-glucuronidase (GUS) reporter gene driven by a 1.5 kb LKP1 promoter display strong GUS activity in leaves. Transgenic plants with a 35S::LKP1 cDNA gene overexpress LKP1 mRNA. These plants have elongated hypocotyls and petioles with elongated cells, and exhibit distinct cotyledon movement during the day. Expression of 35S::LKP1 in transgenic Arabidopsis promotes late flowering in plants grown under long-day, but not under short-day conditions. Vernalization does not affect the late flowering phenotype of the 35S::LKP1 plants. Transgenic plants possessing the 35S::GFP-LKP1 construct also have long hypocotyles and petioles, and a late flowering phenotype, suggesting that the GFP-LKP1 fusion protein is active. The GFP-associated fluorescence in 35S::GFP-LKP1 plants is observed in nuclei and cytosol, indicating that LKP1 is a new nucleo-cytoplasmic factor that influences flowering time in the long day pathway of Arabidopsis.

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