Linkage arrangement of Na,K-ATPase genes in the tetraploid-derived genome of the rainbow trout (Oncorhynchus mykiss)

As part of our efforts to characterize Na,K-ATPase isoforms in salmonid fish, we investigated the linkage arrangement of genes coding for the (alpha) and (beta)-subunits of the enzyme complex in the tetraploid-derived genome of the rainbow trout (Oncorhynchus mykiss). Genetic markers were developed from four of five previously characterized (alpha)-subunit isoforms ((alpha)1b, (alpha)1c, (alpha)2 and (alpha)3) and four expressed sequence tags derived from yet undescribed (beta)-subunit isoforms ((beta)1a, (beta)1b, (beta)3a and (beta)3b). Sex-specific linkage analysis of polymorphic loci in a reference meiotic panel revealed that Na,K-ATPase genes are generally dispersed throughout the rainbow trout genome. A notable exception was the colocalization of two (alpha)-subunit genes and one (beta)-subunit gene on linkage group RT-12, which may thus share a conserved orthologous segment with linkage group 1 in zebrafish (Danio rerio). Consistent with previously reported homeologous relationships among the chromosomes of the rainbow trout, primers designed from the (alpha)3-isoform detected a pair of duplicated genes on linkage groups RT-27 and RT-31. Similarly, the evolutionary conservation of homeologous regions on linkage groups RT-12 and RT-16 was further supported by the map localization of gene duplicates for the (beta) 1b isoform. The detection of homeologs within each gene family also raises the possibility that novel isoforms may be discovered as functional duplicates.