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

Lotus Resources and Genetic Improvement Research Group at Wuhan Botanical Garden 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 displayed 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. Combining yeast two-hybrid system with bimolecular fluorescence complementation assay, they further demonstrated that NnFT2 and NnFT3 proteins could interact with FLOWERING LOCUS D (NnFD) protein, a member of flowering activation complex. Heterologous overexpression of NnFT2 and NnFT3 genes could rescue the late flowering phenotype in Arabidopsis ft-10 mutant, indicating the stimulative roles of NnFTs in floral induction.

This study uncovered the molecular mechanism of NnFTs in the lotus floral transition, which provided theoretical basis and valuable gene 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". SONG Heyun and SUN Heng are the co-first authors. SUN Heng and Prof. YANG Mei are the corresponding authors of the paper. This research was supported by the Biological Resources Program, Chinese Academy of Sciences and the National Natural Science Foundation of China.