CONSERVATION OF FUNCTION AND EXPRESSION OF UNC-119 FROM 2 CAENORHABDITIS SPECIES DESPITE DIVERGENCE OF NONCODING DNA

The Caenorhabditis briggsae homologue of the Caenorhabditis elegans ne uronal gene unc-119 has been cloned by low-stringency hybridization. G enomic clones containing the C. briggsae gene are able to completely r escue the unc-119 phenotype in transgenic C. elegans mutants. The open reading frame (ORF) of the predicted C. briggsae cDNA is 90% identica l to that of C. elegans. Although the splice donor and acceptor sites are conserved, the untranslated regions, and the introns, differ great ly. For this gene, the average intron size in C. elegans is over 600 b ase pairs (bp); in C. briggsae it is only 113 bp. Their upstream contr ol regions share limited sequence similarities; however, reporter gene fusions of the two species show strongly similar expression in C. ele gans. These results are consistent with the maintenance not only of th e function of the unc-119 gene but also the transcriptional control of the gene through tens of millions of years of evolution.