Background Understanding the evolution of novel features requires homology assessments at different levels of biological organization. In flowering plants, floral coronas that play various roles in plant-pollinator interactions have evolved multiple times independently, but are highly variable in their final position and overall morphology. Coronas of the Solanaceae species Jaltomata calliantha are found between the corolla and stamens, adjacent to the gynoecium, and form cups that house copious amounts of their characteristic blood red nectar. To test the hypothesis that J. calliantha coronas evolved as an outgrowth of stamens and therefore have staminal identity, we assessed their development, floral organ identity gene expression, and cellular morphology. Results Jaltomata calliantha coronas emerge after the initiation of all conventional floral organs on the abaxial side of the proximally modified stamens and then expand medially and laterally to form nectar cups. Overlapping expression of the B-class organ identity genes JcAPETALA3 and both JcPISTILLATA/GLOBOSA orthologs (JcGLO1 and JcGLO2), and the C-class-like gene JcAGAMOUS1-like, unites the stamens and corona. Epidermal cell shape also connects the adaxial surface of coronas and petals, and the stamen base, with remaining floral organs showing divergent cell types. Conclusions Our data, based on multiple lines of evidence, support a largely staminal origin for J. calliantha coronas. However, since slightly enlarged stamen bases are found in Jaltomata species that lack coronas, and J. calliantha stamen bases share cell types with petals, we hypothesize that stamen bases recruited part of the petal identity program prior to fully expanding into a corona.

中文翻译：

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Jaltomata calliantha （茄科）花冠在很大程度上起源于雄蕊的证据。

背景 了解新特征的进化需要在生物组织的不同层次上进行同源性评估。在开花植物中，在植物-传粉媒介相互作用中发挥各种作用的花冠已经独立进化了多次，但它们的最终位置和整体形态变化很大。茄科植物 Jaltomata calliantha 的花冠位于花冠和雄蕊之间，与雌蕊相邻，形成杯状，盛放大量特有的血红色花蜜。为了检验 J. calliantha coronas 作为雄蕊的产物进化并因此具有雄蕊特性的假设，我们评估了它们的发育、花器官特性基因表达和细胞形态。结果 Jaltomata calliantha coronas在近端修饰雄蕊背面所有常规花器官萌生后出现，然后向内侧和外侧扩展形成花蜜杯。B 类器官同一性基因 JcAPETALA3 和 JcPISTILLATA/GLOBOSA 直系同源物（JcGLO1 和 JcGLO2）和 C 类基因 JcAGAMOUS1-like 的重叠表达将雄蕊和花冠结合在一起。表皮细胞形状也连接花冠和花瓣的正面以及雄蕊基部，剩余的花器官显示出不同的细胞类型。结论 我们的数据基于多条证据，支持 J. calliantha coronas 的主要后劲起源。然而，由于在缺乏冠的 Jaltomata 物种中发现了略微扩大的雄蕊基部，并且 J. calliantha 雄蕊基部与花瓣共享细胞类型，