Figure 1

Phylogenetic relationships of GPCRs identified in the sponge genome. The tree topology shows distinct phylogenetic clusters belonging to the Glutamate, Rhodopsin, Adhesion, and Frizzled families of the GRAFS classification system. The tree also includes a few representatives of GPCR families from other genomes. The edges are colored according to the families, while the accession IDs are colored differently for each species. The illustration shows putative Adhesion like GPCRs that lacks the conventional long N-termini. However, these Adhesion GPCRs contain the characteristic 7tm_2 domain and placed basal to the major node that contains all the other Adhesions included in the phylogenetic tree making. Sponge specific Rhodopsin clusters (AqRho-A to AqRho-E) within the major Rhodopsin cluster are highlighted.