DUPLICATE SEQUENCES WITH A SIMILARITY TO EXPRESSED GENES IN THE GENOME OF ARABIDOPSIS-THALIANA

The proportion of non-tandem duplicated loci detected by DNA hybridiza tion and the segregation of RFLPs using 90 independent randomly isolat ed cDNA probes was estimated by segregation analysis to be 17%. The 14 cDNA probes showing duplicate loci in progeny derived from a cross be tween Arabidopsis-thaliana ecotypes 'Columbia x Landsberg erecta' dete cted an average of 3.6 loci per probe (ranging from 2 to 6). The 50 lo ci detected with these 14 probes were arranged on a genetic map of 587 cM and assigned to the five A. thaliana chromosomes. An additional du plicated locus was detected in progeny from a cross between 'Landsberg erecta x Niederzenz'. The majority of duplicated loci were on differe nt chromosomes, and when linkage between duplicate locus pairs was det ected, these loci were always separated by at least 15 cM. When partia l nucleotide sequence data were compared with GENBANK databases, the i dentities of 2 cDNA clones which recognized duplicate unlinked sequenc es in the A. thaliana genome were determined to encode a chlorophyll a /b-binding protein and a beta-tubulin. Of the 8 loci carrying beta-tub ulin genes 6 were placed on the genetic map. These results imply that gene duplication has been an important factor in the evolution of the Arabidopsis genome.