Genetic analysis of three lactate dehydrogenase isozyme systems in trout: Evidence for linkage of genes coding subunits A and B

Abstract

AbstractLactate dehydrogenase (LDH) isozymes of two genera within the family Salmonidae (Salvelinus and Salmo) were examined by acrylamide and starch gel electrophoresis. Those species examined contain three isozyme series involving five different kinds of subunits. The A‐B series, believed to be homologous to LDH 1–5 in the majority of vertebrates, is found in nearly all tissues. Polymorphism for subunit B was discovered in Salvelinus fontinalis in which two kinds, B and B', are present within a number of inbred strains. Various crosses and backcrosses involving S. fontinalis and Salvelinus namaycush demonstrate that subunits A and B are each coded by different autosomal genes (LA and LB). A limited amount of test‐cross data indicates linkage of these genes. Partial genetic analysis indicates that a second series of several LDH isozymes, largely restricted to the retina, involves a third subunit, C, in combination with B and to a lesser extent with A. A variant form of subunit C was found in Salmo trutta. Comparison of patterns of S. fontinalis and S. trutta and their hybrid seems to indicate that two additional subunits are involved in a third series of five isozymes found in the skeletal muscle of each species examined.