Clock component OsPRR59 delays heading date by repressing transcription of Ehd3 in rice

Heading date (or flowering time), an important agronomic trait in crop species, is closely associated with regional adaptation and yield. Members of the Pseudo-Response Regulator (PRR) family play key roles in regulating flowering. However, their role and molecular mechanism controlling heading date in rice is not very clear. Here, we identified rice OsPRR protein, OsPRR59, which delayed heading under long-day conditions. OsPRR59 positively regulates yield by affecting plant height, secondary branches number per panicle, grain number per panicle, seed setting rate, and grain weight per plant. OsPRR59 is expressed in most tissues and its protein is localized to the nucleus. We also found that OsPRR59 directly binds to the promoter of Ehd3 to inhibit its expression. Compared with the WT, osprr59 ehd3 showed a significantly delayed heading phenotype, as did the ehd3 mutant. This was opposite to the phenotype of the osprr59 mutant, confirming that Ehd3 acted downstream of OsPRR59 in regulating rice flowering. Our results identified a direct regulator of Ehd3, and revealed a novel molecular mechanism of clock component OsPRR proteins in regulating heading date and provide a new genetic resource for fine-tuning heading date in rice.