Distribution of GST genes over the five Arabidopsis chromosomes. Explosion of the Arabidopsis GST superfamily has occured via tandem gene duplication as well as during chromosomal segmental duplication events. Twenty-five of the 53 genes belonging to the GST superfamily are located within segmentally duplicated regions of the Arabidopsis genome (information derived from TIGR). Connecting coloured lines indicate the segmentally duplicated GST genes. The different GST gene classes are indicated by the varying colours.