Detecting gene fusion. (A) Shown are selected members of the APS_kinase family (seed alignment) with orthologous assignments between the Viridiplantae and the Metazoa group. The proteins of the two clades are orthologous to each other. The A. thaliana protein (KAP2_ARATH) consists of one domain, APS_KINASE. The proteins in the metazoan clade all have an additional domain, ATP_Sulfurylase. (B) The same metazoan proteins are shown as in A, but this time with the orthologous assignments displayed for the ATP_Surylase domain (full alignment, here the ATP_Surylase domain has a tree icon). Because both domains in the metazoan proteins have orthologous single-domain proteins in A. thaliana, this indicates a gene fusion in an early metazoan ancestor that lead to the bifunctional metazoan proteins.
