Induction of dwarf and early flowering phenotypes in Tricyrtis sp. by ectopic expression of LEAFY from Arabidopsis thaliana.

LEAFY (LFY), which encodes a plant-specific transcription factor, plays an important role in the transition from vegetative to reproductive development. Ectopic expression of LFY has been reported to induce dwarfism and early flowering in some model plants. In order to examine the possibility of using LFY for molecular breeding of ornamental plants, we produced and characterized transgenic plants ectopically expressing LFY from Arabidopsis thaliana (AtLFY) in the liliaceous ornamental plant Tricyrtis sp. Nine independent transgenic plants have been obtained, and all of them exhibited dwarf phenotypes compared with the vector control. These transgenic plants could be classified into three types according to the degree of dwarfism: one showed an extreamly dwarf phenotype with smaller leaves (Type I); two showed moderately dwarf phenotypes (Type II); and six showed slightly dwarf phenotypes (Type III). All of Type I, Type II and Type III transgenic plants produced flower buds 1-3 weeks earlier than the vector control. Vector control and Type III transgenic plants produced 1-4 apical flower buds, whereas Type I and Type II transgenic plants produced only a single apical flower bud. Type I and Type II transgenic plants often produced non-fully-opened flowers. Quantitative real-time reverse transcription-polymerase chain reaction analysis showed that the AtLFY expression level generally correlated with the degree of dwarfism. These results indicate that morphological alterations observed in the transgenic plants was induced by ectopic expression of AtLFY. Lower levels of ectopic expression of LFY may be valuable for producing dwarf and early flowering ornamental plants.