ELD1 mediates photoperiodic flowering via OsCCA1 alternative splicing and interacts with phytochrome signaling in rice

Photoperiodic flowering in plants is orchestrated by the dynamic interaction between light signals and the endogenous circadian clock, but how light signals integrate into the clock remains to be fully elucidated. Here, we identify ELD1, a CCHC-type zinc finger protein that is essential for rice embryo survival. Notably, partial loss of ELD1 function results in early flowering under long-day conditions. Further investigations demonstrate that ELD1 physically interacts with OsNKAP, an orthologue of mammal NF-κB activating protein, as well as core splicing factors to regulate the splicing profile of OsCCA1, a core oscillator of the circadian clock. Molecular and genetic evidence indicate that OsCCA1 is the primary target of ELD1 in controlling flowering time. Additionally, ELD1 interacts with photoactivated phyB, mediating red-light-regulated alternative splicing of OsCCA1. Collectively, our findings establish a molecular connection between light signaling and the circadian clock, with ELD1 modulating OsCCA1 alternative splicing to control photoperiodic flowering.