Phylogenetic and Molecular Evolutionary Investigations of Chloroplast DNA Variation in the Campanulaceae sensu stricto

University Of Texas At Austin, Austin TX

Investigators

Abstract

9982091 Jansen Genomic (DNA) data are helping to revolutionize the study of taxonomic relationships, classification, and evolutionary affiliations of organisms. In addition to DNA sequence data (strings of nucleotides from comparable, or homologous, genes), restriction-site data and other kinds of gene-order data are also valuable and powerful sources of evidence. Dr. Jansen at the University of Texas has been a leader in the development of restriction-site and gene-order methods in the analysis of phylogenetic relationships of plants. In this project he and a team of colleagues will study the plant family Campanulaceae (the bellflower family), where the chloroplast genome has the greatest known range of structural or gene-order variants of any flowering plant family, including cases of inversion, expansion/contraction of the IR region (the Inverted Repeat characteristic of all land plant chloroplast genomes), gene transpositions, gene losses, and deletions within large open reading frames. Most of these changes are expected to be rare if not unique events, at the molecular level, and are thus potentially strong markers of sublineages within the family. In many cases, however, the proposed rearrangements must be confirmed by direct nucleotide sequencing of end points or other "hot spots" to ensure comparison of equivalent changes. The project thus combines analyses in the field of molecular evolution with efforts to construct a framework phylogeny for the 30-50 genera of Campanulaceae and an improved classification of these. Dr. Jansen is working with a network of colleagues and collectors around the world to secure samples of all of the known genera of the family, and extended samples within the large genera such as Campanula and Wahlenbergia. Abundant preliminary data have been gathered, in conjunction with former students and other colleagues. DNA sequence data from both chloroplast and nuclear genes are being gathered to generate a phylogeny independent of the rearrangement evidence, and to integrate with morphological characters from traditional taxonomic studies. A recently trained specialist on the group, Dr. William Eddie from Scotland, will likely join the laboratory in Texas, bringing both data from molecular systematic analyses of the chloroplast matK gene and morphological expertise as well. Success in determining the sequence of structural events in repatterning the chloroplast genome of Campanulaceae will help improve generic classification, provide insight to historical biogeography of the family including origins of the numerous island endemics, and help in understanding the evolution of floral form and pollination.