DHD6 Delays Flowering in Rice by Negatively Regulating the Expression of Ehd1

Heading date, also known as flowering time, plays a crucial role in determining the regional adaptability of rice (<i>Oryza sativa</i> L.). Heading date is regulated by numerous genes involved in various photoperiod pathways. Here, we isolated the <i>Delayed Heading Date 6</i> (<i>DHD6</i>) gene from a whole-genome-sequenced rice mutant population. We demonstrated that a 2 bp deletion in the coding region of <i>DHD6</i> truncates the protein and confers early flowering. Genetic analysis shows that <i>DHD6</i> functions upstream of <i>Ehd1</i> and is synergistic with <i>Se14</i> and <i>PHYC</i> to regulate flowering time. In addition, we identified natural alleles of <i>DHD6</i> that are associated with heading date and likely contribute to the geographic adaptation of rice. In summary, DHD6 functions upstream of <i>Ehd1</i>, reducing the transcriptional level of <i>Ehd1</i>, thereby delaying flowering.