9811362 dePamphilis Support is requested to study the history of a Group I intron found at an identical location in the mitochondrial gene cytochrome oxidase I (coxI) of diverse flowering plants. The intron is homologous with and has key structural elements of a well-studied infectious intron in fungi. The intron occurs in numerous unrelated lineages of flowering plants, while being absent from the vast majority of flowering plants examined. Surprisingly, the intron is particularly concentrated in parasitic plants, which have intimate symbiotic associations with other plants and fungi. This pattern, and features of the biology of parasitic plants, suggests the possibility that some parasitic plants are capable of incorporation of foreign DNA sequences and/or may have played a role as an intron source in genetic transfers to host lineages. The proposed research will test biologically-based hypotheses that may explain the presence and movement of the coxI intron among plant lineages. The data collected will define the precise distribution of the intron across parasitic and nonparasitic plant groups, the genic and cellular location of the sequences, and phylogenetic comparisons of coxI intron and exon sequences. A second mitochondrial gene, atpA, will also be examined, to improve the phylogenetic resolution and reliability of the coxI exon (ie., plant mitochondrial) history. This research will represent the first comprehensive analysis of a plant mitochondrial gene and its intron; the results will have important implications for our understanding of organelle genetics, mobile genetic elements, and fundamental problems of molecular evolution and systematics. In addition, the broader significance of this project to society includes: 1) Training of undergraduate, graduate, and postdoctoral scientists; 2) Potential for the identification of invasive genetic elements in plant organelle sequences, 3) Development of phylogenetic approaches to the study of intr ons that may have broader application to understanding other invasive elements in biology, agriculature, and medicine; 4) Contributing to an understanding of parasitic plants, which could aid efforts to control harmful parasitic weeds in agriculture.
