Researchers Identify Cells that Trigger Flowering

How do plants "know" it is time to flower? For a long time, no one has identified the cells which produce the small protein called Flowering Locus T (FT). A new study conducted by researchers from Cornell University uncovers exactly where the key protein forms before it triggers the flowering process in plants.

Flowering in many plants begins when the leaves perceive day-length. It was previously known that in Arabidopsis plants, long day-length starts a process where leaves synthesize and transmit FT in the plant's vascular tissue, which carries sugars and nutrients from leaves to the rest of the plant. FT travels to the shoot apex, the highest point of new leaves and stems, where it promotes the formation of flowers. Flowering regulation is complex as the release of FT is controlled by more than 30 proteins in interacting cascades. Identifying FT-producing cells was difficult because leaf veins are very small and covered by photosynthetic cells rich in chlorophyll.

The researchers discovered that FT was also produced in the same type of companion cells in the phloem of Maryland Mammoth tobacco. When these companion cells were killed, it delayed flowering in both Arabidopsis and the tobacco plants. When the researchers looked more closely at the pathways that lead to flowering, they found that killing these companion cells stopped FT's downstream process, but not its upstream, confirming that FT originates in these cells and that the synthesis of FT is regulated by an extensive intercellular signaling system.

Read more about this research in the Cornell Chronicle.