Chloroplast genomes of land plants are generally considered to be highly conserved in structure, gene order and content, with notable exceptions in the conifers and a few representatives in angiosperm families, such as the Campanulaceae, Fabaceae, Geraniaceae, and Lobeliaceae. Previous gene mapping has shown that the chloroplast genomes of Trachelium and 17 other members of the family Campanulaceae are the most highly rearranged chloroplast genomes among land plants. Hypotheses of evolutionary mechanisms for these structural changes have included inversions, transpositions, gene loss, insertions and deletions, and expansion and contraction of the inverted repeat. We recently sequenced and annotated the entire chloroplast genome of Trachelium caeruleum. Our methods included the development of a new chloroplast genome annotation program and the identification of elements that may have been responsible for changes in gene order. The sequence data confirm the early gene mapping studies of Cosner et al. and indicate that this genome has experienced numerous structural changes, some of which represent novel events not reported for other chloroplast genomes. More importantly, the sequence data have helped clarify some of previous hypotheses of the mechanisms of cpDNA rearrangements. Chloroplast genome sequencing of several other species of the Campanulaceae is in progress. Genomic data integrated with molecular phylogenies of the Campanulaceae will clarify patterns and mechanisms of cpDNA evolution in this family.

Key words: Campanulaceae, chloroplast genome, comparative genomics, molecular evolution