Florigen activation complex forms via multifaceted assembly in Arabidopsis.

Area of Science:

• Plant molecular biology
• Developmental biology
• Genetics

Background:

• Florigen (FT) protein, synthesized in leaves, induces flowering by signaling to the shoot apical meristem (SAM).
• 14-3-3 proteins and FD transcription factor are proposed to mediate FT's action by forming a floral activation complex (FAC).

Purpose of the Study:

• To elucidate the precise mechanism of floral activation complex (FAC) assembly.
• To investigate the diverse roles of 14-3-3 proteins in FAC formation and function.
• To understand the spatiotemporal distribution and function of the FAC during floral development.

Main Methods:

• Biochemical assays to analyze protein-protein interactions.
• In vitro studies on protein complex formation and DNA binding.
• Analysis of gene expression patterns in floral primordia.

Main Results:

• FT interacts with a pre-formed DNA-FD-14-3-3 complex via two interfaces, with its C-terminus binding DNA.
• 14-3-3 proteins facilitate FD DNA binding by reducing its liquid phase condensation and promoting dimerization.
• FT and FD are co-transcribed in young floral primordia, establishing a boundary and initiating FAC formation during early floral development.

Conclusions:

• A novel mechanism for FAC assembly is proposed, involving direct interaction of FT with the DNA-bound FD-14-3-3 complex.
• 14-3-3 proteins play multifaceted roles in regulating FD DNA binding and FT recruitment.
• The spatiotemporal co-expression of FT and FD in floral primordia is crucial for initiating floral development.