Genomic organization of the glutathione S-transferase family in insects

► Insect cytosolic glutathione S-transferases confirmed as mainly members of six major subclasses. ► Epsilon subclass has early origin along endopterogote lineage. ► Delta subclass has an earlier origin in Insecta. ► Confirmed that many glutathione S-transferase genes cluster by genomic position. ► Pattern of gene expansions largely explained by the number of genes in genome.