AUTHOR=Peng Xin , Tun Win , Dai Shuang-feng , Li Jia-yue , Zhang Qun-jie , Yin Guo-ying , Yoon Jinmi , Cho Lae-hyeon , An Gynheung , Gao Li-zhi 

TITLE=Genome-Wide Analysis of CCT Transcript Factors to Identify Genes Contributing to Photoperiodic Flowering in Oryza rufipogon

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.736419

DOI=10.3389/fpls.2021.736419

ISSN=1664-462X

ABSTRACT=<p>Photoperiod sensitivity is a dominant determinant for the phase transition in cereal crops. <italic>CCT</italic> (<italic>CONSTANS, CO-like, and TOC1</italic>) transcription factors (TFs) are involved in many physiological functions including the regulation of the photoperiodic flowering. However, the functional roles of <italic>CCT</italic> TFs have not been elucidated in the wild progenitors of crops. In this study, we identified 41 <italic>CCT</italic> TFs, including 19 <italic>CMF</italic>, 17 <italic>COL</italic>, and five <italic>PRR</italic> TFs in <italic>Oryza rufipogon</italic>, the presumed wild ancestor of Asian cultivated rice. There are thirty-eight orthologous <italic>CCT</italic> genes in <italic>Oryza sativa</italic>, of which ten pairs of duplicated <italic>CCT</italic> TFs are shared with <italic>O. rufipogon</italic>. We investigated daily expression patterns, showing that 36 <italic>OrCCT</italic> genes exhibited circadian rhythmic expression. A total of thirteen <italic>OrCCT</italic> genes were identified as putative flowering suppressors in <italic>O. rufipogon</italic> based on rhythmic and developmental expression patterns and transgenic phenotypes. We propose that <italic>OrCCT08</italic>, <italic>OrCCT24</italic>, and <italic>OrCCT26</italic> are the strong functional alleles of rice <italic>DTH2</italic>, <italic>Ghd7</italic>, and <italic>OsPRR37</italic>, respectively. The SD treatment at 80 DAG stimulated flowering of the LD-grown <italic>O. rufipogon</italic> plants. Our results further showed that the nine <italic>OrCCT</italic> genes were significantly downregulated under the treatment. Our findings would provide valuable information for the construction of photoperiodic flowering regulatory network and functional characterization of the <italic>CCT</italic> TFs in both <italic>O. rufipogon</italic> and <italic>O. sativa</italic>.</p>