Hox genes of salmonids
Hox cluster organization provides a valuable marker for studying the effects of WGD in salmonids. For most teleosts with three rounds of WGD, the Hox gene clusters should number 7 or 8 (McArthur et al. 2003; Stellwag 1999). However, we found that the number of Hox gene clusters in salmonids was 13, includingHoxAaα , HoxAaβ , HoxAbα , HoxBaα ,HoxBaβ , HoxBbα , HoxBbβ , HoxCaα ,HoxCaβ , HoxCbα , HoxCbβ , HoxDaα , andHoxDaβ (Figure 3 ). HoxAbβ appears to have been lost in the common ancestor of all salmonids because the most ancient salmonid species (B. l. tsinlingensis ) does not possess the HoxAbβHox cluster. With the exception of the assembly quality of salmonids, the 13 Hox clusters in salmonids were highly similar, which indicates that the Hox clusters were likely derived from a single common ancestor.