Evolutionary study of peta-like organ in Angiosperms

花的形态发生模型被称为ABC模型，作为突变花的分子遗传分析的结果，被广泛提倡和接受。ABC模型也适用于水稻的花，水稻的花与拟南芥的花结构不同，似乎适用于大多数被子植物。鱼腥草的花由3个雄蕊和3个心皮组成，没有花被。但是，它们在花序的底部有一个白色的花瓣状器官，被称为总苞片，因为它们附着在花序的最低位置。在本研究中，我们重点研究花瓣状器官形成的机制，特别是ABC模式是否参与了这种总苞片的形成，或者它是通过不同的进化过程获得的。由此，我们克隆并鉴定了棉桃MADS-box基因。然后用定量RT-PCR和原位杂交检测各基因的表达。结果表明，在山茱萸总苞片中存在API组、PI组、AP3组和SEP组基因的表达。这些基因表达的组合已成为确定拟南芥花瓣器官身份的必要条件。这一结果提示，灯心草花瓣状苞片可能与拟南芥花瓣具有相似的决定机制。

The morphogenesis model of the flower, which is called the ABC model, had been advocated and, is widely accepted as the result of molecular genetic analyzes of mutant flowers. The ABC model is also applicable to the flower of rice, which has a different structure from those of Arabidopsis, and is seems to be fit in most angiosperms.The flower of Houttuynia cordata consists of 3 stamens and 3 carpels, and have no perianth. But, they have a white petal-like organ at the base of the inflorescence ,which is called the involucral bract, because they are attached to the lowest position of inflorescence. In this study, we focused on mechanism of petal-like organ formation, especially whether the ABC model having participated in this involucral bract formation, or it had acquired with different evolution process. Thus, the MADS-box genes had been cloned and characterized in H. cordata. Then, expression of each gene was inspected by quantity RT-PCR and in situ hybridization. As a result, expression of the genes belonging to the API group, the PI group, the AP3 group and the SEP group had been observed in the involucral bract of the H. cordata. As for combination of these gene expressions, it has become clear to be necessary sufficient ones to determination of the organ identity of the petals in Arabidopsis thaliana. This result suggests the possibility that the petal-like bract of H. cordata has similar detemination mechanism to the petal of Arabidopsis.