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Originally published in Science Express on 6 November 2008
Science 5 December 2008:
Vol. 322. no. 5907, pp. 1535 - 1539
DOI: 10.1126/science.1163927
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Reports

Photoexcited CRY2 Interacts with CIB1 to Regulate Transcription and Floral Initiation in Arabidopsis

Hongtao Liu, Xuhong Yu, Kunwu Li, John Klejnot, Hongyun Yang, Dominique Lisiero, Chentao Lin*

Cryptochromes (CRY) are photolyase-like blue-light receptors that mediate light responses in plants and animals. How plant cryptochromes act in response to blue light is not well understood. We report here the identification and characterization of the Arabidopsis CIB1 (cryptochrome-interacting basic-helix-loop-helix) protein. CIB1 interacts with CRY2 (cryptochrome 2) in a blue light–specific manner in yeast and Arabidopsis cells, and it acts together with additional CIB1-related proteins to promote CRY2-dependent floral initiation. CIB1 binds to G box (CACGTG) in vitro with a higher affinity than its interaction with other E-box elements (CANNTG). However, CIB1 stimulates FT messenger RNA expression, and it interacts with chromatin DNA of the FT gene that possesses various E-box elements except G box. We propose that the blue light–dependent interaction of cryptochrome(s) with CIB1 and CIB1-related proteins represents an early photoreceptor signaling mechanism in plants.

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90095, USA.

* To whom correspondence should be sent. E-mail: clin{at}mcdb.ucla.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)