Why Sequence a Liverwort?

The origin of land plants (embryophytes) was one of the major evolutionary events in the history of planet earth. Experimental, paleontological, morphological, and molecular systematic data all point to the liverworts as being some of the first plants to evolve and colonize the Ordovician landscape. Thus liverworts are a key group to include in any comparative study aimed at understanding the origin and evolution of organisms that now cover much of terrestrial earth. Marchantia polymorpha is a common, easily cultivated liverwort that exhibits many primitive characteristics of both liverworts and land plants. M. polymorpha has been widely studied by researchers in physiology, anatomy, and genetics and is included as the exemplar in most phylogenetic analyses of land plants.

The M. polymorpha genome sequence will be useful in several ways. The recent sequencing of Selaginella moellendorffii and Physcomitrella patens genomes has already made genomic comparisons at deeper phylogenetic levels possible. Since liverworts have convincingly been resolved as the sister group to all other land plants, the addition of a liverwort genome will allow genomic comparisons that span the breadth of extant embryophyte diversity. The ability to compare genomes of a liverwort, a moss, a lycophyte, and several flowering plants will provide critical insight into the similarities and differences in developmental, structural, and physiological genes in plants with strikingly different morphologies and life histories.

Combining access to a sequenced genome with techniques being developed to study and manipulate genes in M. polymorpha will allow this plant to become a model organism for understanding the genetics of development in a plant that may be as close a living example as possible of what an ancient land plant might have been, making it possible to identify the suite of genes that are common to all land plants. As a representative genome from the sister lineage to all other land plants, the genome of M. polymorpha will be as significant for understanding land plant evolution as the genomes from the choanoflagellate Monosiga brevicollis and the lancelet Branchiostoma floridae (both recently released by the JGI) are to understanding evolution of the metazoan and vertebrate clades.

Principal Investigator: John Bowman and Sandra K. Floyd (Monash Univ.), Takayuki Kohchi and Hideya Fukuzawa (Kyoto Univ.), and Kanji Ohyama (Ishikawa Prefectural Univ.)