Sequence analysis of the 125-Mb nuclear genome of the model plant Arabidopsis thaliana has uncovered 25,498 genes, representing about 11,000 gene families. Most of the gene families are similar to those found in other eukaryotes, but several hundred are unique to the plant kingdom. These include over 800 genes, primarily involved in photosynthetic activities, that seem to have been acquired from the cyanobacterial endosymbiont that evolved into the chloroplast. Among the unusual properties of the Arabidopsis genome are a fairly uniform gene density in all but centromeric and heterochromatic regions, numerous small and large genomic duplications, and other types of rearrangement. The genomic sequence now provides the raw material for comprehensive analyses of gene function in plants, and will provide powerful opportunities to compare and contrast with the genetic complements of animals, fungi, prokaryotes and other plant species.
