Arabidopsis arrives

Sequence analysis of the 125-Mb nuclear genome of the model plant Arabidops is thaliana has uncovered 25,498 genes, representing about 11,000 gene fami lies. Most of the gene families are similar to those found in other eukaryo tes, but several hundred are unique to the plant kingdom. These include ove r 800 genes, primarily involved in photosynthetic activities, that seem to have been acquired from the cyanobacterial endosymbiont that evolved into t he chloroplast. Among the unusual properties of the Arabidopsis genome are a fairly uniform gene density in ail but centromeric and heterochromatic re gions, numerous small and large genomic duplications, and other types of re arrangement. The genomic sequence now provides the raw material for compreh ensive analyses of gene function in plants, and will provide powerful oppor tunities to compare and contrast with the genetic complements of animals, f ungi, prokaryotes and other plant species.