GENOME DNA-SEQUENCING AROUND THE EF-1-ALPHA MULTIGENE LOCUS OF ARABIDOPSIS-THALIANA INDICATES HIGH GENE DENSITY AND A SHUFFLING OF NONCODING REGIONS

In Arabidopsis thaliana, EF-1 alpha proteins are encoded by a multigen e family of four members. Three of them are clustered at the same locu s, which was positioned 24 cM from the top of chromosome 1. A region o f DNA spanning 63 kb around these locus was sequenced and analyzed. On e main characteristic of the locus is the mosaic organization of both genes and intergenic regions. Fourteen genes were identified, among wh ich only four were already described, and other unidentified are most likely present. Functionally diverse genes are found at close interval s. Exon and intron distribution is highly variable at this locus, one gene being split into at least 20 introns. Several duplications were f ound within the sequenced segment bath in coding and noncoding regions , including two gene families. Moreover, a sequence corresponding to t he 5' noncoding region of the EF-1 alpha genes and harboring a 5' inte rvening sequence is duplicated and found upstream of several genes, su ggesting that noncoding regions can be shuffled during evolution.