DISSERTATION RESEARCH: Phylogenetically-Based Analysis of Plastid Genome Evolution in the Photosynthetically Variable Parasitic Flowering Plant Genus, Cuscuta

宾夕法尼亚州立大学（Pennsylvania State University）的克劳德·德帕姆菲利斯（Claude dePamphilis）博士和乔尔·麦克尼尔（Joel McNeal）先生获得了一笔拨款，用于研究一组被称为dodders的寄生植物的不同物种之间是如何相互关联的，以及产生光合作用所需蛋白质的基因在物种间是如何不同的。菟丝子是一种藤蔓植物，只有细小无用的叶子，没有根，附着在其他植物的茎上，依赖这些寄主提供所有的水、无机营养物质，以及大部分（如果不是全部的话）所需的碳水化合物。由于这种习惯，寄生虫对自身光合作用的需求减少了。位于叶绿体（植物细胞的光合室）内的基因在开花植物中是高度保守的，因为这些基因中的大多数是从阳光和大气二氧化碳中产生碳水化合物所必需的。然而，这些基因在不同的菟丝子之间存在很大程度的差异，这表明不同的物种可能表现出不同的光合作用能力。通过研究不同菟丝子物种和相关非寄生植物叶绿体中哪些基因保存良好，可以了解哪些基因对光合作用最重要，哪些基因更容易被消耗。这些数据将通过与其他寄生植物谱系的比较进一步验证。此外，了解菟菟子物种之间的关系可能最终被证明对控制这些寄生杂草是有价值的，其中许多对农业造成严重损害，是联邦指定的有毒杂草。从营养独立到寄生的转变已经在植物和许多其他生命谱系中发生过无数次。这种寄生植物群将作为一个极好的模型来研究伴随这种转变的遗传变化。

A grant has been awarded to Dr. Claude dePamphilis and Mr. Joel McNeal at Pennsylvania State University to study how different species of a group of parasitic plants known as dodders are related to each other and how genes that produce proteins necessary for photosynthesis differ between species in the lineage. Dodders, which are vines that possess only tiny, useless leaves and no roots whatsoever, attach to the stems of other plants and are dependent on these hosts for all of their water, inorganic nutrients, and most, if not all, of their carbohydrate needs. Because of this habit, the parasites have a reduced need to photosynthesize for themselves. Genes located within chloroplasts, the photosynthetic compartments of plant cells, are highly conserved across flowering plants because most of these genes are necessary for carbohydrate production from sunlight and atmospheric carbon dioxide. However, a large degree of variation exists in these genes between different dodders, indicating that different species may demonstrate differing abilities to photosynthesize. By examining which genes are well conserved within chloroplasts of different dodder species and related non-parasitic plants, an understanding of which genes are most important for photosynthesis and which genes are more expendable will be gained. These data will be verified further by comparison with other parasitic plant lineages. Furthermore, knowledge of the relationships between dodder species may eventually prove to be valuable to the control of these parasitic weeds, many of which do serious agricultural damage and are federally designated noxious weeds. The transition from being nutritionally independent to being parasitic has occurred numerous times within plants and also within many other lineages of life. This parasitic plant group will serve as an excellent model to study the genetic changes that accompany this transition.