Lifschitz Eliezer, Professor - Emeritus
Florigen is a global growth regulator and developmental status communicator
The origin and diversification of elaborated shoot systems in flowering plants was likely escorted by global communication systems that inform adjacent and remote growth zones on overall developmental status, but no such system was ever described. We hypothesize that a florigen-based system abides by all tenets of such a global regulatory and communication hierarchy and offer the scientific rational to resolve it.
Our studies of flowering and shoot architecture in tomato have established the florigen protein as a universal mobile growth hormone. Gene dosage analysis of SINGLE FLOWER TRUSS, the gene encoding florigen, and of its potent antagonist, SELF-PRUNING, showed that organ–specific SFT/SP ratios, as opposed to absolute levels, generate prepatterns in which meristematic transcription networks and the classic growth hormones auxin and cytokinin operate to determine growth and termination in all above ground meristems. Using grafting, florigen was shown to modify, systemically, local SFT/SP ratios in target organs. In leaves such a change promotes maturation thus endorsing the export of florigen to new sink organs and communicating the state of the source organ.
The florigen-based SFT/SP ratio is unique among proportional controls in that unlike other in animals it regulates growth vs. termination in every aerial meristem and that the proportions are maintained, long-range, by systemic regulation. The developmental plasticity provided by the modular organization of the sympodial shoots, the sympodial inflorescences and the compound leaves of tomato, along with the genetic resources and ease of grafting, facilitates the integrative analysis of global communication systems.
Our experimental programs include:
A) Identifying the universal cellular pathways and genetic networks monitoring and characterizing the response of meristems to florigen and to changing SFT/SP ratios.
B) Unraveling the genetic networks and auxin / CK patterning oscillations associated with the vegetative/reproductive periodicity of the sympodial program.
C) Discovering the genetic regulators, molecular design and spatial targets of the florigen apparatus.
D) Elucidating the mechanisms underlying the antagonistic functions of SP and the functional evolution of florigen as a growth hormone.