A CRY-BIC negative-feedback circuitry regulating blue light sensitivity of Arabidopsis.

Cryptochromes are blue light receptors that regulate various light responses in plants. Arabidopsis cryptochrome 1 (CRY1) and cryptochrome 2 (CRY2) mediate blue light inhibition of hypocotyl elongation and long-day (LD) promotion of floral initiation. It has been reported recently that two negative regulators of Arabidopsis cryptochromes, Blue light Inhibitors of Cryptochromes 1 and 2 (BIC1 and BIC2), inhibit cryptochrome function by blocking blue light-dependent cryptochrome dimerization. However, it remained unclear how cryptochromes regulate the BIC gene activity. Here we show that cryptochromes mediate light activation of transcription of the BIC genes, by suppressing the activity of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), resulting in activation of the transcription activator ELONGATED HYPOCOTYL 5 (HY5) that is associated with chromatins of the BIC promoters. These results demonstrate a CRY-BIC negative-feedback circuitry that regulates the activity of each other. Surprisingly, phytochromes also mediate light activation of BIC transcription, suggesting a novel photoreceptor co-action mechanism to sustain blue light sensitivity of plants under the broad spectra of solar radiation in nature. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Citation

Xu Wang, Qin Wang, Yun-Jeong Han, Qing Liu, Lianfeng Gu, Zhaohe Yang, Jun Su, Bobin Liu, Zecheng Zuo, Wenjin He, Jian Wang, Bin Liu, Minami Matsui, Jeong-Il Kim, Yoshito Oka, Chentao Lin. A CRY-BIC negative-feedback circuitry regulating blue light sensitivity of Arabidopsis. The Plant journal : for cell and molecular biology. 2017 Nov;92(3):426-436

PMID: 28833729

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