Petals can be simple or elaborate, depending on whether they have lobes, teeth, fringes, or appendages along their margins, or possess spurs, scales, or other types of modifications on their adaxial/abaxial side, or both. Elaborate petals have been recorded in 23 orders of angiosperms and are generally believed to have played key roles in the adaptive evolution of corresponding lineages. The mechanisms underlying the formation of elaborate petals, however, are largely unclear. Here, by performing extensive transcriptomic and functional studies on Nigella damascena (Ranunculaceae), we explore the mechanisms underlying elaborate petal development and specialized character formation. In addition to the identification of genes and programs that are specifically/preferentially expressed in petals, we found genes and programs that are required for elaborate rather than simple petal development. By correlating the changes in gene expression with those in petal development, we identified 30 genes that are responsible for the marginal/ventral elaboration of petals and the initiation of several highly specialized morphological characters (e.g., pseudonectaries, long hairs, and short trichomes). Expression and functional analyses further confirmed that a class I homeodomain-leucine zipper family transcription factor gene, Nigella damascena LATE MERISTEM IDENTITY1 (NidaLMI1), plays important roles in the development of short trichomes and bifurcation of the lower lip. Our results not only provide the first portrait of elaborate petal development but also pave the way to understanding the mechanisms underlying lateral organ diversification in plants.

花瓣可以是简单的，也可以是精致的，这取决于它们的边缘是否有裂片，牙齿，条纹或附肢，或者在其前/后侧具有刺，鳞片或其他类型的修饰，或两者兼而有之。精巧的花瓣已被记录在23个被子植物的科目中，通常被认为在相应谱系的适应性进化中起着关键作用。然而，精细花瓣形成的机制尚不清楚。在这里，通过对黑夜蛾Nigella damascena进行广泛的转录组学和功能研究（毛un科），我们探讨了花瓣精心发育和特殊性状形成的机制。除了鉴定在花瓣中特异性/优先表达的基因和程序外，我们还发现了精心制作而不是简单花瓣发育所需的基因和程序。通过将基因表达的变化与花瓣发育中的那些相关联，我们鉴定了30个基因，这些基因负责花瓣的边缘/腹面细化和几种高度专门化的形态特征（例如假腺，长发和短毛状体）的起始。表达和功能分析进一步证实了I类同源域-亮氨酸拉链家族转录因子基因Nigella damascena LATE MERISTEM IDENTITY1（NidaLMI1）在短毛状体的形成和下唇的分叉中起重要作用。我们的结果不仅提供了精心制作的花瓣发育的第一张画像，而且还为理解植物中侧向器官多样化的机制铺平了道路。