FLZ13 Interacts with FLC and ABI5 to Negatively Regulate Flowering Time in Arabidopsis

The transition from vegetative to reproductive growth, known as flowering, is a critical developmental process in flowering plants to ensure reproductive success. This process is strictly controlled by various internal and external cues; however, the underlying molecular regulatory mechanisms need to be further characterized. Here, we report a plant-specific protein, FCS-LIKE ZINC FINGER PROTEIN 13 (FLZ13), which functions as a hitherto unknown negative modulator of flowering time in Arabidopsis thaliana. Biochemical analysis showed that FLZ13 directly interacts with FLOWERING LOCUS C (FLC), a major flowering repressor, and that FLZ13 largely depends on FLC to repress the transcription of two core flowering integrators: FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1. In addition, FLZ13 works together with ABSCISIC ACID INSENSITIVE 5 to activate FLC expression to delay flowering. Taken together, our findings suggest that FLZ13 is an important component of the gene regulatory network for flowering time control in plants.