Lotus is one of the top ten traditional flowers in China with high ornamental value. Flowering behavior in lotus marks the transition from vegetative to reproductive growth, and flowering time is also an important determinant of its market value.

Previous comparative transcriptome data of lotus buds at different developmental stages revealed that the FLOWERING LOCUS T (FT) gene, namely NnFT, was the significant differentially expressed gene, hinting its key role in the lotus flower formation. However, the function of NnFT genes and their molecular mechanisms of lotus flowering remain largely unknown. 

Researchers from the Wuhan Botanical Garden of the Chinese Academy of Sciences (CAS) found eight NnFT homologous genes, designated as NnFT1-NnFT8, in the Asian lotus genome. Two NnFT homologs, NnFT2 and NnFT3, were the major preponderantly expression genes, which showed rich transcript abundance in floral-related organs and leaves.

In addition, the proNnFT:β-glucuronidase (GUS) assay exhibited GUS staining in the vascular tissues of leaves. By combining the yeast two-hybrid system with a bimolecular fluorescence complementation assay, they further demonstrated that NnFT2 and NnFT3 proteins could interact with the FLOWERING LOCUS D (NnFD) protein, a member of the flowering activation complex.

Moreover, heterologous overexpression of NnFT2 and NnFT3 genes could rescue the late flowering phenotype in Arabidopsis ft-10 mutant, indicating the stimulatory roles of NnFTs in floral induction.  

This study reveals the molecular mechanism of NnFTs in the lotus flowering transition, providing theoretical basis and valuable genetic resources for the genetic improvement of lotus flowering time.  

These results were published in the Plant Physiology and Biochemistry with the title of "FLOWERING LOCUS T genes control floral induction in lotus."

This work was supported by the Biological Resources Program of CAS and the National Natural Science Foundation of China.