苞片是花序结构中的变态叶，部分植物的苞片具有类似花瓣的色彩和形态，能够与花瓣协同 (或代替花瓣) 实现吸引传粉者等功能，称之为花瓣状苞片。花瓣状苞片体现了植物对环境的高度适应，在一定程度上驱动了物种的分化，对被子植物的多样性的形成具有极为重要的意义。花瓣状苞片的演化机制十分复杂,被子植物不同世系的花瓣状苞片可能是多次独立演化的产物，本项目对花瓣状苞片遗传调控机制和演化模式提出了两个假设 ：（1） 花瓣状苞片的多样性是由于相似的基因在表达时间和表达量上的不同导致的。不同世系的花瓣状苞片之间存在共有的基因表达模式和调控网络。（2）不同世系的花瓣状苞片是由不同的基因和调控网络控制的，在基因层面不存在深度同源和平行演化。为了验证这两个假设，本项目拟对来自被子植物不同世系的七种拥有花瓣状苞片的植物进行研究，通过转录组测序和差异表达分析等手段，探讨花瓣状苞片的遗传调控机制和演化模式。

A bract is a modified or specialized leaf in inflorescence. Some bracts are brightly colored and serve the function of attracting pollinators, either together with the perianth or instead of it. Usually, we described such bracts as petaloid bracts. The origin and evolution of petaloid bracts may have important significance to angiosperm diversification, which lead to ecological innovation and drive speciation. The form of petaloid bracts exemplifies a complex hierarchical evolutionary history, and it may have evolved independently multiple times in different lineages of angiosperm. In this research, we considering two hypotheses: (1) the petaloid bracts in different lineages follow a similar genetic program that involves the expression of a set of organ identity genes that control the development at a specific place and time. (2) The modification of petaloid bracts among lineages is the results of different genes in the network, and there is no deep homology and parallel evolution in gene expression evolution of petaloid bracts. In order to test these two hypotheses, we plan to research seven species with petaloid bracts through comparative transcriptome sequencing. This project allows us a better understanding of the genetic regulation and evolution of petaloid bracts.