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

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. <i>LEAFY</i> (<i>LFY</i>), 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. <i>Tricyrtis</i> spp., which belong to the family Liliaceae, show two different types of inflorescence architecture: <i>T</i>. <i>hirta</i> produces both apical and lateral flowers, whereas <i>T</i>. <i>formosana</i> produces only apical flowers. In the present study, we isolated <i>LFY</i>-homologous genes from <i>T</i>. <i>hirta</i> and <i>T</i>. <i>formosana</i> (designated as <i>ThirLFY</i> and <i>TforLFY</i>, respectively) and analyze their functions and expression patterns as a first step toward elucidation of molecular mechanisms of inflorescence architecture determination in <i>Tricyrtis</i> 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 <i>Arabidopsis thaliana</i> plants overexpressing <i>ThirLFY</i> or <i>TforLFY</i> showed early flowering and production of secondary inflorescences, and no functional differences were observed between ThirLFY and TforLFY. <i>In situ</i> hybridization analysis showed that <i>ThirLFY</i> was expressed in both apical and lateral buds of <i>T</i>. <i>hirta</i>, whereas <i>TforLFY</i> was only expressed in apical buds of <i>T</i>. <i>formosana</i>. Thus, two different types of inflorescence architecture in <i>Tricyrtis</i> spp. may be caused by different expression patterns of <i>LFY</i>-homologous genes.