In the latest issue of Nature Genetics (volume 22; in July 1st 1999) the first ever-established complete clone-based physical map of a plant genome is published. The work was conducted in the group of Dr. Thomas Altmann at the Max Planck Institute of Molecular Plant Physiology, Golm, in collaboration with groups at the Max Planck Institute of Molecular Genetics, Berlin, Germany, the University of Pennsylvania, Philadelphia, and the Washington University, St. Louis, USA. The map covers the entire nuclear genome of the higher plant Arabidopsis thaliana. Furthermore, this map is the first ever assembled (for any organism) entirely on the basis of BAC (bacterial artificial chromosome) clones, the premier system for cloning and maintenance of large genomic DNA.
A physical map of a genome shows the localisation of all cloned DNA-segments of an organism in relative order and distribution over the different chromosomes. The existing Arabidopsis physical maps were predominantly based on YACs (yeast artificial chromosomes, a system for cloning and maintenance of large DNA fragments). The map presented here is highly reliable and offers strongly increased resolution, due to the properties of the BAC cloning system. It is a representation of the entire Arabidopsis genome as a set of 8,285 overlapping BAC clones. The sequence analysis of these BAC clones, currently being done in the framework of the International Arabidopsis Genome Initiative, will lead to elucidation of the complete genomic DNA sequence within the next years. To date, complete genomic DNA sequences are available only for yeast and several prokaryotic microorganisms. Arabidopsis thaliana - a small flowering plant which is also called Thale’s cress and which possesses a very small genome of only 5 chromosomes - is the major model system for plant molecular genetics. The most important benefit of the physical map lies in its support for map-based gene cloning experiments. Novel genes identified, will not only provide insight into the molecular mechanisms of plant function, but will also offer the means to generate the future 3rd and 4th generation of genetically engineered crops (this view is evidently supported by the strong investments of the agro-biotech industry into Arabidopsis research). From this point of view, major achievements in Arabidopsis genome research are of interest to the plant research community, the general research community as well as the general public.
Prior to publication the results announced here were continuously presented to the plant research community in the Arabidopsis database of the Max Planck Institute of Molecular Plant Physiology in Golm, Germany. The demand in the public and private plant research communities for this information is demonstrated by the fact that the web site displaying the map data has already been accessed by several hundred users from all over the world (http://www.mpimp-golm.mpg.de/101/mpi_mp_map/access.html). Thanks to the willingness of many colleagues within the Arabidopsis research community by providing individual information to be integrated into the map and the attitude of all the co-authors to make all information instantaneously available to the research community, an extraordinary model of international collaboration has been demonstrated.
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