| Summary: | Heading date, as one of the most important agronomic traits, is a fundamental factor determining crop yield. Although diverse genes related to heading date have already been reported in rice, the key gene that regulates heading date is still poorly understood. Here, we identified a heading date regulator, heading date 8 (<i>OsHd8</i>), which promoted the heading date under long-day conditions and encoded a putative HAP3 subunit of the CCAAT-box-binding transcription factor. It is localized in the nucleus and expressed in various tissues. Sequence analysis revealed that there were four SNPs and one InDel in the promoter region of <i>OsHd8</i>, which was involved in the regulation of some floral regulators including <i>GHD7.1</i>, <i>SDG718</i>, <i>OsGI</i> and <i>HDT1</i>. Further evolutionary analysis showed that <i>OsHd8</i> presents divergence between <i>indica</i> and <i>japonica</i>, showing natural selection during the domestication of cultivated rice. These results indicate that <i>OsHd8</i> plays an important role in the regulation of heading date, and may be an important target for rice breeding programs.
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