Abstract

Emergence of land plants, approximately 480 million years ago, was one of the major events for the life on planet earth. Experimental, paleontological, morphological, and molecular systematic data all support that liverworts represent the earliest land plant. Liverworts are a key group to understand the genetic basis of the key innovations that allowed green plants to evolve from aquatic ancestors and to adapt to life on land1). Marchantia polymorpha is a common, well-propagating, dioecious liverwort species, and the haploid gametophytic generation dominates over the diploid sporophytic generation in its life cycle. The organellar genomes and the Y chromosome of M. polymorpha were the first to be sequenced in plants2), and the whole-genome shotgun-sequencing project has been launched recently at the Joint Genome Institute in USA . We focus on the potential of M. polymorpha as a model plant for molecular genetics, and have been developing crucial experimental procedures and resources. We have found that growth condition rich in far-red light promotes transition to the reproductive phase, which has made crosses in laboratory possible3). Linkage analysis on M. polymorpha can be done with an F1 population instead of F2 due to its haploidy, and a genetic map have been constructed using >100 markers based on DNA polymorphisms between our two laboratory lines. We have also developed an efficient transformation system for M. polymorpha using Agrobacterium tumefaciens4). It is easy to monitor M. polymorpha cells developing from a single-celled spore under various conditions. Our system founded on M. polymorpha should contribute to fundamental understanding of the regulatory mechanisms that mediate plant development and responses to various environmental factors. As an example, I would like to show also our recent work on auxin signaling in the basal land plant M. polymorpha.

References: 1. Bowman J.L. et al. (2007) Cell 129, 229-234 2. Yamato K.T. et al. (2007) Proc. Natl. Acad. Sci. USA 104 , 6472-6477 3. Chiyoda S. et al. (2008) Plant Cell Rep. 27, 1467-1473 4. Ishizaki K. et al. (2008) Plant Cell Physiol. 49, 1084-1091