Cuicui Shen, Haiyang Liu, Zeyuan Guan, Yan Junjie, Zheng Ting, Wenhao Yan, Changyin Wu, Qifa Zhang, Ping Yin, Yongzhong Xing

The Plant Cell, Published August 2020. DOI: https://doi.org/10.1105/tpc.20.00067

Abstract

CCT (CONSTANS, CONSTANS-LIKE and TOC1) domain-containing proteins are a large family unique to plants. They transcriptionally regulate the processes related to photoperiodic flowering, circadian rhythms, vernalization, and other related functions. CO (CONSTANS) and HD1 (HEADING DATE 1), through the CCT domain, coordinate with the NF-YB/YC dimer to specifically target a conserved 'CCACA' motif within the downstream promotor. However, the mechanism underlying the DNA recognition by CCT domain remains unclear. Here we determined the crystal structures of the rice NF-YB/YC dimer and the florigen Hd3a-bound HD1CCT/NF-YB/YC trimer with resolutions of 2.0 Å and 2.55 Å, respectively. The CCT domain of HD1 displays an elongated structure containing two (alpha)-helices and two loops, tethering the Hd3a to the NF-YB/YC dimer. Helix (alpha)2 and loop 2 are anchored into the minor groove of the 'CCACA' motif, which determines the specific base recognition. Our structures reveal the interaction mechanism among the CCT domain, NF-YB/YC dimer, and the target DNA. These results not only provide new insights into the network between the CCT proteins and NF-Y subunits, but also offer references for improving productivity and global adaptability of crops by manipulating florigen expression.

全文链接：http://www.plantcell.org/content/early/2020/08/25/tpc.20.00067