Beyond flowering time: pleiotropic function of the maize flowering hormone florigen.

The transition from vegetative to reproductive development is a critical turning point in a plant’s life cycle. It is now widely accepted that a leaf-borne signal, florigen, moves via the phloem from leaves to the shoot apical meristem to trigger its reprogramming to produce flowers. In part, the florigenic signal comprises a protein that belongs to the phosphatidylethanolamine-binding protein (PEBP) family that is present in all living organisms but displays diverse functions. The founding floral-promoting PEBP gene in Arabidopsis is FLOWERING LOCUS T (FT) whose functional homologs have been indentified in many flowering plants. We recently accumulated sufficient evidence to demonstrate the maize FT homolog ZCN8 has florigenic function. This task was particularly challenging due to the large number of FT-homologous genes in the maize genome. Here we show that ZCN8 function is more complex than simply regulating the floral transition. ZCN8 appears to play a pleiotropic role in the regulation of generalized growth of vegetative and reproductive tissues.