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.
evolutionary developmental biology