Isolation and characterization of LEAFY-homologous genes from two Tricyrtis spp. showing different inflorescence architecture.

Abstract

For ornamental plants, inflorescence architecture is one of the most important traits to determine their commercial values. However, molecular mechanisms of inflorescence architecture determination have not yet been fully elucidated. LEAFY (LFY), which encodes a plant-specific transcriptional factor, has been shown to play a key role in the switch from vegetative to reproductive phases. Recent studies have demonstrated that LFY is involved not only in floral meristem induction but also in inflorescence architecture determination. Tricyrtis spp., which belong to the family Liliaceae, show two different types of inflorescence architecture: T. hirta produces both apical and lateral flowers, whereas T. formosana produces only apical flowers. In the present study, we isolated LFY-homologous genes from T. hirta and T. formosana (designated as ThirLFY and TforLFY, respectively) and analyze their functions and expression patterns as a first step toward elucidation of molecular mechanisms of inflorescence architecture determination in Tricyrtis spp. Alignment analysis based on amino acid sequences showed that both ThirLFY and TforLFY have functional motifs of LFY, and only three amino acid differences are found between them. Transgenic Arabidopsis thaliana plants overexpressing ThirLFY or TforLFY showed early flowering and production of secondary inflorescences, and no functional differences were observed between ThirLFY and TforLFY. In situ hybridization analysis showed that ThirLFY was expressed in both apical and lateral buds of T. hirta, whereas TforLFY was only expressed in apical buds of T. formosana. Thus, two different types of inflorescence architecture in Tricyrtis spp. may be caused by different expression patterns of LFY-homologous genes.