FLOWERING LOCUS T genes control floral induction in lotus.

The transition to flowering is a vital process in the lotus life cycle that significantly impacts its ornamental value and seed production. However, the molecular basis of floral transition in lotus remains largely unknown. Here, eight homologous FLOWERING LOCUS T (FT) genes were initially characterized in lotus, which were designated as NnFT1-NnFT8. All of these genes were found to possess the conserved PEBP domain and exhibited high transcript levels in both lotus leaves and floral organs. The proNnFT:β-glucuronidase (GUS) assay exhibited GUS staining in the vascular tissues of leaves. Furthermore, subcellular localization revealed that NnFT proteins were present in various cellular organelles, including the nucleus, cytoplasm, and endoplasmic reticulum. Overexpression of two NnFT homologs, NnFT2 and NnFT3, rescued the late flowering phenotype in the Arabidopsis ft-10 mutant, indicating the stimulative roles of NnFTs in floral induction. Moreover, NnFTs demonstrated interactions with a bZIP transcription factor, FLOWERING LOCUS D (NnFD), both in vitro and in vivo. These findings will not only deepen our understanding of the regulatory mechanism underlying lotus floral transition, but also provide valuable genetic resources for creating new lotus varieties with extended blooming periods using molecular strategies in the future.