Abstract
摘要：許多有關植物發育遺傳學方面的研究，都集中在植物最顯著的構造﹣花上。被子植物的花部形態變異非常大，也顯然由複雜的機制所調控。近年來，由於在模式植物中對於開花相關基因的研究有著長足的進展，許多研究的興趣也漸漸延伸到一些其他的植物上。類花瓣是植物一種特化的構造，通常是在該植物上有著極為顯著的花萼或苞片，取代了原有花瓣吸引傳粉者的功能。本實驗所使用的材料﹣四照花，即是一個典型的例子。四照花具有四片白色的大苞片圍繞著它的花序，而這四個苞片在顏色及功能上都與正常花瓣類似，因此我們推測這些苞片可能有著和控制花瓣的調控機制相類似，甚至使用相同的系統。以在阿拉伯芥中的研究為例，若提高控制花瓣基因的表現量，則原先長葉之處會長出像花瓣的構造，因此若改變花瓣控制基因的表現地區，非花瓣的器官也可能生成類似花瓣的構造。本實驗目的即是在鑑定四照花中調控類花瓣苞片的基因，並藉由基因表現分析及本屬其他植物之比較研究，進而瞭解類花瓣構造的發育及演化。本實驗之結果亦有相當高之應用性，對於園藝上的品種改良，可以提供分子遺傳上的基礎。
Abstract: Studies of plant developmental genetics have been largely focused in the floral structure, the most elaborated organ of flowering plants. There are also growing interests on understanding the diverse floral morphologies among different groups of plants other than the model systems people are usually working on. One of the particularly interesting topics is the petaloid structure that mimics the function of showing petals. Such petaloid structures are found in many flowering plants and one of the most famous examples is the showy bracts of dogwoods (Cornus). The showy bracts of dogwoods have many petal features, such as bright color and shining surface, that suggest these bracts may share certain developmental programs of normal petals. The molecular basis of the development of petaloid structures is either the same as in petals, or simply has its own system. However, based on recent molecular studies on floral genes in Arabidopsis, the petaloidy could be simply explained by an ectopic expression of genes that control petal development in certain organs, because overexressing petal identity genes can convert leaves to petaloid structures. Therefore, the showy bracts of dogwoods could be the similar case that it has common components as in the petal development. Our approach is to identify and characterize the expression patterns of the petal-controlling genes in the showy-bracted and bractless dogwoods, and also examine other potential homeotic genes that are expressed in the petaloid bracts of dogwoods. The identified sequences will also be used for phylogenetic analysis of the genus Cornus. The proposed work is very important in understanding petal development and ontogenetics of petaloidy in dogwoods. Since petaloid structures have evolved independently several times in angiosperms, our result will certainly provide great information about the evolutionary developmental programs of petals and have many applications on other ornamental plants.
Keyword(s)
四照花
分子演化
類花瓣構造
演化發育學
Cornus
molecular evolution
petaloid structure
evolutionary developmental biology
