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