Abstract:

The glutathione S-transferases (GSTs) belong to a superfamily in which almost 100 sequences have been identified from more than 20 species of insects. All the GST genes belong to at least 3 classes, Ⅰ(Delta) class, Ⅱclass and Ⅲ (Epsilon) class, among which Ⅰand Ⅲ are insectspecific class. Genes in GST classⅠare usually encoded by multigene family and the complexity in different species of insects are variable. Fewer genes in GST classⅡare reported; their genomic organization is simple, generally having only one copy. Class Ⅲ are newly identified class and their genomic organization is only clear in Drosophila melanogaster and Anopheles gambiae. Mechanisms of gene cluster, alternative splicing and gene fusion are involved in generating multiple functional GST genes. There are two molecular mechanisms for increased expression of GSTs in resistant insects: elevation in mRNA level and gene amplification while the latter is rarely reported. Elevation of GST activity is involved in upregulation of multiple enzymes belonging to one more GST classes or more rarely upregulation of a single enzyme. The expression is regulated by trans-acting regulators and cis-acting regulating elements. So far only a few crude chromosomal locations which should contain these regulatory genes and some putative regulatory elements have been identified.

Key words: Glutathione S-transferase, insect, gene structure, expression regulation