Evolution of patterns of differential gene expression: A comparison of the temporal and spatial patterns of lsozyme locus expression in two closely related fish species (northern largemouth bass, Micropterus salmoides salmoides, and Smallmouth Bass, Micropterus dolomieui)

The timing of the onset of developmental expression of 33 loci encoding various enzymes and isozymes was determined for two closely related species of fish, the northern largemouth bass, Micropterus salmoides salmoides, and the smallmouth bass, M. dolomieui. The patterns of gene expression among the different tissues in adults were also investigated. The tissue and developmental expressions of these enzymes and isozymes were visualized by histochemical staining after starch gel electrophoresis. The differential expression of homologous loci within and among the different adult tissues of these two related species is virtually identical. The ontogenetic times of expression during the embryogenesis of both species are also quite similar for these same homologous loci. The ontogenetic patterns of differential gene expression for these two species differ somewhat from those of a more distantly related species within the family Centrarchidae, the green sunfish, Lepomis cyanellus. These results are consistent with the hypothesis that there is an increase in divergence of gene expression in species which are progressively more distantly related.