title: Organisation and structural evolution of the rice glutathione S-transferase gene family.
abstract: Glutathione S-transferases (GSTs) comprise a large family of key defence enzymes against xenobiotic toxicity. Here we describe the comprehensive characterisation of this important multigene family in the model monocot species rice [ Oryza sativa(L.)]. Furthermore, we investigate the molecular evolution of the family based on the analysis of (1) the patterns of within-genome duplication, and (2) the phylogenetic relationships and evolutionary divergence among rice, Arabidopsis, maize and soybean GSTs. By in-silico screening of the EST and genome divisions of the Genbank/EMBL/DDBJ database we have isolated 59 putative genes and two pseudogenes, making this the largest plant GST family characterised to date. Of these, 38 (62%) are represented by genomic and EST sequences and 23 (38%) are known only from their genomic sequences. A preliminary survey of EST collections shows a large degree of variability in gene expression between different tissues and environmental conditions, with a small number of genes (13) accounting for 80% of all ESTs. Rice GSTs are organised in four main phylogenetic classes, with 91% of all rice genes belonging to the two plant-specific classes Tau (40 genes) and Phi (16 genes). Pairwise identity scores range between 17 and 98% for proteins of the same class, and 7 and 21% for interclass comparisons. Rapid evolution by gene duplication is suggested by the discovery of two large clusters of 7 and 23 closely related genes on chromosomes 1 and 10, respectively. A comparison of the complete GST families in two monocot and two dicot species suggests a monophyletic origin for all Theta and Zeta GSTs, and no more than three common ancestors for all Phi and Tau genes.
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133, Milano, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Soranzo
authors.forename: M
authors.initials: M
authors.lastname: Sari Gorla
authors.forename: L
authors.initials: L
authors.lastname: Mizzi
authors.forename: G
authors.initials: G
authors.lastname: De Toma
authors.forename: C
authors.initials: C
authors.lastname: Frova
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D020440:Gene Duplication; D015870:Gene Expression; D017343:Genes, Plant; D005982:Glutathione Transferase / Q000235:genetics*; D005810:Multigene Family; D012275:Oryza / Q000235:genetics*; D010802:Phylogeny; D013025:Glycine max / Q000235:genetics; D003313:Zea mays / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D005982:Glutathione Transferase