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SUSTech researchers reveal a novel molecular mechanism underlying light and the circadian clock mediated development in plants

DATE:2020-08-03

On 30th July, 2020, Chair Professor Xing Wang Deng (Biology) led his research team to publish a paper in the high-impact academic journal, Plant Cell (IF=9.618). Their article, entitled “COLD-REGULATED GENE 27 integrates signals from light and the circadian rhythm to promote hypocotyl growth in Arabidopsis”, showed a novel regulation of seedlings photomorphogenesis by the integration of light signal and thecircadian clock.


As the essential externalor internal cues, light and the circadian clock are critical for the survival and development of plants. While germinating under soil absence of light signal, seedlings undergo skotomorphogenesis, characterized by accelerated hypocotyl elongation, closed and etiolated cotyledon, and apical hook. This development process enables seedlings to promptly receive the light. Upon exposure to the light, seedlings undergo photomorphogenesis, characterized by inhibited hypocotyl elongation, open and greening cotyledon, and disappeared apical hook.


COP1-SPA complex is the key repressor of light signaling, it functions as an E3 ligase to promote downstream substrates  ubiquitination and degradation. A group of transcription factors play key roles in the regulation of photomorphogenesis. bZIP type transcription factor HY5 and bHLH type transcription factor PIF4 antagonistically regulate photomorphogenesis. HY5acts as a positive regulator of light signaling, while PIF4 represses photomorphogenetic development. The researchers in this study identified a new repressor of light signaling, COR27. COR27 integrated light and the circadian clock signaling to modulate the growth and development in Arabidopsis. In the light, accumulated COR27 protein repressed DNA-binding capacity of HY5 through a direct protein-protein interaction. On the other hand, COR27 could directly bind to the promoter region of PIF4 to promote the expression of PIF4 and its target genes specifically in the afternoon. Consequently, COR27 promoted hypocotyl elongation at least in part through these two characterized molecular regulatory mechanisms. In the dark, COP1-SPA complex promoted the degradation of COR27 via the 26S proteasome system. This study revealed a novel mechanism underlying the regulation of photomorphogenesis by COR27-mediated integration of light and the circadian clock signals (Fig. 1).

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Fig. 1 A working model depicting the regulation of photomorphogenesis by COR27-mediated integration of light and circadian clock signaling


Senior Research Assistant Wei Zhu and Hua Zhou (Institute of Plant and Food Science) are the co-first authors. Professor Xing Wang Deng at SUSTech and Professor Dongqing Xu at Nanjing Agricultural University are the co-corresponding authors.

This research received support from SUSTech, the National Key R&D Program of China, the National Natural Science Foundation of China, Peking-Tsinghua Center for Life Sciences, Nanjing Agricultural University, Nanjing Science and Technology Innovation Program for Overseas Students, and the Jiangsu Collaborative Innovation Center for Modern Crop Production.

 

Link to paper: http://www.plantcell.org/content/early/2020/07/30/tpc.20.00192