Dictyosteliumchromosome

Dictyostelium discoideum occupies a unique position at the border between free-living cells and multicellular organisms. In the July 4 Nature, the Dictyostelium Genome Sequencing Consortium reports the sequencing of the largest chromosome, chromosome 2, from the D. discoideumgenome (Nature 2002, 418:79-85). The chromosome is approximately 8 megabases long, representing about a quarter of the genome. The sequence is extremely A+T rich, averaging 86% in intergenic regions. The researchers predicted 2,799 coding genes and 73 tRNA genes, and extrapolate to estimate a total gene number of 11,000 Dictyostelium genes. About 35% of genes had a match in other eukaryote genomes. The high gene density is similar to that found in yeast. The Consortium notes that the Dictyostelium genome appears more similar to metazoa than to plants or fungi. Further analysis of the Dictyostelium genome will undoubtedly provide insights into how it has evolved for unicellular and multicellular life.