Comparative transcriptome analysis reveals the molecular mechanism underlying lily double flowering

Flower morphology is a vital ornamental characteristic. A single flower is the main floral pattern for lily, and rare double-flowered lily has extremely high ornamental and commercial value. However, the genetic basis underlying the double flowering of lily remains unknown. Here, with Lilium lancifolium and a double-flowered lily mutant used as experimental materials, RNA-seq was performed to elucidate the molecular mechanism of double-flowered lily. DEG enrichment highlighted the effect of hormone signal transduction pathways on stamen petaloidy. A large number of genes and TFs involved in hormone signal transduction pathways were identified. In particular, in the auxin biosynthesis and signaling pathway, most of the key genes were upregulated in double-flowered lily. In addition, comparative transcriptome and gene expression pattern analyses revealed that two MADS family members and a C2H2 gene may play vital roles in the transformation from single- to double-flowered lily. This study provides insights into the complex molecular networks underlying floral organ development in double-flowered lily.