Insights into the structural and functional evolution of plant genomes afforded by the nucleotide sequences of chromosomes 2 and 4 of Arabidopsis thaliana

The rapidly accumulating genome sequence data from the plant Arabidopsis th aliana allows more detailed analysis of genome content and organisation tha n ever before possible in plants. The genome shows a surprisingly high leve l of genetic redundancy, with as many as 75% of gene products showing signi ficant homology to another protein of A. thaliana, Many duplicated genes oc cur in arrays of conserved order and indicate that A. thaliana is likely to have had a tetraploid ancestor. Analysis of the divergence of duplicated g enome segments leads to the prediction of two major modes of plant genome e volution: macroscale duplication and rearrangement of chromosomes and micro -scale translocations, duplication and loss of individual genes or small gr oups of genes. Copyright (C) 2000 John Wiley & Sons, Ltd.