Lipids bind to florigen and control flowering time

A research team led by Dr. Yuki Nakamura, an Assistant Research Fellow at the Institute of Plant and Microbial Biology, Academia Sinica, recently discovered that a flowering inducer florigen binds phospholipid and promote flowering in Arabidopsis.

A flowering-inducing hormone, or florigen, is a long-distance mobile protein produced in leaves that acts to initiate flowering. For its critical role, florigen was studied intensively worldwide, and revealed to be small mobile protein acting as a complex which was named the “florigen activation complex”. However, to date, what sort of molecules florigen interacts with to fulfill its role to initiate flowering is still poorly understood.

Dr. Nakamura's team hypothesized, based on the 3D structure of florigen, that phospholipids might represent novel binding partners of florigen to modulate its function. Here, they found that phosphatidylcholine (PC) bound specifically to florigen. To investigate the role of PC in flowering, they developed a new technology to engineer PC levels at the shoot apex. They found that increases in PC where florigen acts, promote flowering, whereas decreases in PC delay flowering time. This effect was attenuated if florigen was genetically knocked out. They further discovered that PC molecular species oscillated diurnally, and night-dominant species were not the preferred ligands for florigen. Metabolic engineering to increase night species during the day time delayed the flowering time in the presence of florigen. Thus, Nakamura's team concluded that florigen binds to diurnally oscillating phospholipids and accelerate flowering.

The study proposed a novel model of flowering time control by lipids, which provides a new direction for agricultural innovation such as improved crop yields or efficient bioenergy creation. The research was funded by Academia Sinica and Japan Science and Technology Agency, and was conducted in collaboration with Honor. Prof. Dr. George Coupland (Max-Planck-Institute for Plant Molecular Breeding, Germany) and Prof. Dr. Peter Dörmann (Univ. Bonn, Germany).