Functional Evolution Of Glutathione S-transferase Gene Family From Selaginella Moellendorffii

Glutathione S-transferases(GSTs, EC 2.5.1.18) is a kind superfamily of proteins which widespread existences in organisms.It has important functions of detoxifying stress tolerance, in response to stress and signal transductio in vivon. Previous studies on the GST gene family in plants have focused on bryophytes (such as Physcomitrella patens), gymnosperms (such as Pinus tabulaeformis Carr) and angiosperms (such as Populus trichocarpa), lack of research on the pteridophyte.In this study, we acted Selaginella moellendorffii as an object, used the methods of the search sequence, phylogenetic analysis, molecular cloning, protein expression and purification and enzyme activity assay, analysed on the GST family of genes, molecular evolution, gene expression, protein function in Selaginella moellendorffii. Obtained results are as follows:1. We have identified a total of 65 full-length GST genes from the whole genome of Selaginella moellendorffii, which were divided into 10 classes, including Tau, Phi, DHAR, Theta, Zeta, Lambda, EF1By, Ure2p, TCHQD, Hemerythrin and Iota. All of 65 genes had typical GST domain by conserved domain prediction.2. Tau class GST subfamily had the most members in Selaginella moellendorffii. In all land plants, only the lowest like moss Physcomitrella patens did not exist Tau class GST, the other four kinds of vascular plants had the largest number of Tau class GST, suggesting that Tau class GST may have originated in vascular plants. By chromosomal localization, we found that Tau class GST was rapid expansion by tandem repeats way in the Selaginella moellendorffii genome. For Phi class GST,, there was more than eight members in other terrestrial species, but only two copies in Selaginella moellendorffii. Addition, analysis of two Phi class GSTs activity performed at different pH and temperature conditions found that the two proteins had high catalytic activity between pH 7 and 8.5, and between 45 and 55℃, indicating that the two proteins were capable of functioning at a relatively wide environmental conditions change, also suggesting that the two Phi class GST genes plays an important role in adapting to the complex terrestrial environment for Selaginella moellendorffii.3. Tissue-specific expression pattern analysis found that 41 genes were all expressed in roots, stems and leaves,20 genes was expression part of the three organizations, four genes (SmGSTU14, SmGSTU22, SmGSTU47, SmGSTT1) in the three organizations were not expression, indicating that genes expression patterns of GST gene family have diverged in Selaginella moellendorffii.4. Induced expression and activity determination of 12 recombinant GST proteins found that they had catalytic activity towards CDNB, while no catalytic activity is not detected towards DHA, and different proteins have different substrate spectrum, the catalytic activities of a substrate was difference in the same subfamily and between different subfamilies, indicating that there is a clear functional differentiation between GST gene family members in Selaginella moellendorffii.Comprehensive gene sequence, gene structure, phylogeny, tissue-specific expression patterns, biochemical analysis of protein function, This paper found that Selaginella moellendorfii GST gene family existed a functional differentiation at different levels of gene sequence, gene structure, tissue specificity expression, protein biochemical functions. Through systematic analysis and chromosome mapping, this paper revealed the complex evolutionary patterns of GST gene family in land plants.