Phylogenetic relationship among rice and Arabidopsis GST proteins and their classification. The unrooted tree was constructed based on multiple sequence alignment of full-length protein sequences using ClustalX program by neighbor-joining method with 1000 bootstrap replicates. The numbers at the nodes represent bootstrap values (≥ 500) from 1000 replicates. All the rice and Arabidopsis GST proteins grouped into seven classes. The bar indicates 0.1 substitutions per site. The cluster of Tau class GST genes present only in rice is indicated in box.