Cytokinin Oxidase/Dehydrogenase 1 (FvCKX1) Coordinates Receptacle Growth and Achene Maturation in Strawberry

The coordinated development of achenes and receptacles in strawberry is critical for seed dispersal and fruit quality, yet the underlying molecular mechanisms remain poorly characterized. Utilizing RNA-seq analysis during the ripening transition stage, we identified pronounced transcriptomic divergence between achenes and receptacles, with receptacles exhibiting more dynamic gene expression shifts. Intriguingly, a substantial subset of differentially expressed genes (DEGs) displayed antagonistic expression patterns between these tissues, including the cytokinin degradation gene cytokinin oxidase/dehydrogenase 1 (FvCKX1), which was highly expressed in both tissues but with opposing temporal trends. Functional interrogation via transient silencing and overexpression revealed a tissue-specific regulatory role for FvCKX1. RNA interference (RNAi) suppression of FvCKX1 significantly enhanced receptacle expansion but delayed achene maturation, whereas overexpression inhibited receptacle growth while accelerating achene ripening. Abscisic acid (ABA), which positively regulates fruit enlargement, was elevated in FvCKX1 RNAi receptacles and notably reduced in overexpression fruits, indicating that FvCKX1 might negatively modulate ABA synthesis during strawberry fruit development. Our results demonstrate that FvCKX1 may function as a key regulator mediating the coordinated development between achenes and receptacles in strawberry.