The FLOWERING LOCUS T-like genes from patchouli (Pogostemon cablin) antagonistically regulate flowering time

Flowering is crucial for the reproductive success of plants. Patchouli (Pogostemon cablin), a widely utilized medicinal and aromatic plant from the Lamiaceae family, exhibits rare flowering and fails to produce seeds, thereby posing a challenge for plant evolution and breeding improvement. However, the mechanism underlying flowering in patchouli has not been investigated. FLOWERING LOCUS T (FT) serves as a central integrator of flowering signals. Here, we identified 13 patchouli FT-like genes (PatFTs). In patchouli leaves, PatFT10-13 displayed continuous expression, with a decline noted at the flowering stage, while PatFT1-3 were activated exclusively at the flowering stage, and PatFT4-9 were hardly expressed. Overexpression of PatFT2 in Arabidopsis induced early flowering, while overexpression of PatFT10-13 resulted in delayed flowering. These results suggested that PatFT1-3, differing by one to two unique residues in the non-conserved region, might function as floral inducers, while PatFT10-13 likely act as floral repressors. Both PatFT2 and PatFT11 interacted with patchouli FD-like proteins. Transient expression of PatFT11 in protoplasts reduced the ability of PatFT2 to activate downstream flowering genes, suggesting a competitive antagonism between these proteins for shared interactors. Amino acid swapping analysis indicated that specific conserved residues was responsible for the functional switch in PatFTs. Furthermore, we revealed that the evolution of antagonistic FT-like modules might represent a common strategy for Lamiaceae plants to fine-tune flowering time. In summary, these findings provide new insights into the expansion and functional diversity of FT-like genes in patchouli.