An important piece in the evolutionary puzzle of plants
Recently, the characterization of non-seed vascular plants has taken a giant step forward with the decoding of the complete genome of a spike moss (Selaginella moellendorffii) by an international consortium led by Dr. Jo Ann Banks from Purdue University (USA). Two researchers from the University of Freiburg, Dr. Stefan Rensing and Andreas Zimmer (Faculty of Biology), contributed to the analysis of the genome by performing a classification and phylogenetic analysis of the encoded transcription factors as well as by checking for potential genomic contaminations. The results are published in the current issue of the journal Science.
This genome, sequenced by the Joint Genome Institute of the U.S. Department of Energy, is expected to give scientists a better understanding of how plants of all kinds evolved over the past 500 million years. Banks, a professor of botany and plant pathology, led a team of about 100 scientists from 11 countries to sequence the genome of this lycophyte, representing the oldest living vascular plants. There are only three families and about 1.000 species of lycophytes remaining. Selaginella has been on Earth about 200 million years and is a real survivor.
The Selaginella genome, with about 22,300 genes, is relatively small. Scientists also discovered that Selaginella is the only known plant not to have experienced a polyploidy event, in which it creates extra sets of chromosomes. In comparing this genome sequence with others, researchers were able to identify genes that are present only in vascular plants and genes present only in flowering plants. These genes likely played important roles in the early evolution of vascular plants and flowering plants, respectively. Many of these genes have unknown functions, but it is likely that those genes that are present only in flowering plants may function in the development of fruits and seeds, which are important to agriculture.
Selaginella and Arabidopsis, a plant widely used in research, use significantly different genes to control creation of secondary metabolites, molecules that are responsible for creating scents, seed dispersal functions, defense and other tasks. Those secondary metabolites also are used to create pharmaceuticals. The metabolic genes evolved independently in Selaginella and flowering plants, so the metabolites they make are likely to be very different. This means Selaginella could be a huge resource for new pharmaceuticals.
