A CLUSTER TYPE ORGANIZATION OF THE LOCI OF THE IMMUNOGLOBULIN LIGHT-CHAIN IN ATLANTIC COD (GADUS-MORHUA L) AND RAINBOW-TROUT (ONCORHYNCHUS-MYKISS WALBAUM) INDICATED BY NUCLEOTIDE-SEQUENCES OF CDNAS AND HYBRIDIZATION ANALYSIS

Antibody screening and colony hybridization of cDNA libraries have bee n used to isolate clones of the immunoglobulin light (IgL) chain from Atlantic cod (Gadus morhua L.) and rainbow trout (Oncorhynchus mykiss Walbaum). Sequence analysis-shows dissimilarities in the constant part of the molecule (CL) within each species. Comparisons of the amino ac id sequences of the constant parts of the IgL chains show a 55% identi ty between the two teleost species. When compared with other species t he highest similarities are found to the constant domain of the IgL ch ain from mammals (30% - 37%), but the teleost IgL chain can be classif ied neither as kappa nor lambda. The V(L) domain in Atlantic cod and r ainbow trout is also more similar to those of mammals than to those of other animal species, but no difference between kappa and lambda was noticed. Genomic Southern blots hybridized with fragments coding for t he constant part of IgL gave several bands larger than 2 kilobases and a similar pattern was obtained with fragments coding for the variable part. These results show that the locus of the IgL chain has a multip le organization in teleost fish and that the locus has an organization similar to that of sharks. Several of the cDNA clones isolated from b oth the head kidney and the spleen represent nonrearranged or nonsplic ed mRNA, and northern blot analysis shows that such transcripts are pr esent in both the head kidney and the spleen.