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Glutathione S-transferase (GST) is important in plants to resist various stresses. In this study, two Phi GST genes (SmGSTF1 and SmGSTF2) were cloned from Selaginella moellendorffii. SmGSTF1 and SmGSTF2 genes encode proteins of 215 amino acid residues. Gene expression analysis showed that the two genes were expressed in roots, stems and leaves. The recombinant SmGSTF1 and SmGSTF2 proteins were overexpressed in Escherichia coli, and purified by Ni-affinity chromatography. SmGSTF1 and SmGSTF2 had the catalytic activity towards 1-Chloro-2,4-Dieitrobenzene, 4-Chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl), and 4-Nitrobenzyl chloride substrates. SmGSTF1 also had the activity towards Fluorodifen and Cumyl hydroperoxide (Cum-OOH), whereas SmGSTF2 not. The enzyme kinetics analysis showed that SmGSTF1 and SmGSTF2 had high affinity towards glutathione, and low affinity towards 1-Chloro-2, 4-Dieitrobenzene. The enzymatic activity of SmGSTF1 and SmGSTF2 had high catalytic activity between pH 7 and 8.5, and between 45 and 55 °C. SmGSTF1 and SmGSTF2 may have an important role in the resistance of Selaginella moellendorfii against stress.

Plant dehydroascorbate reductase (DHAR) is a physiologically important reducing enzyme in the ascorbate-glutathione recycling reaction. In this study, two DHARs genes (SmDHAR1 and SmDHAR2) were isolated from Selaginella moellendorffii. The SmDHAR1 and SmDHAR2 genes encode two proteins of 218 and 241 amino acid residues, with a calculated molecular mass of 23.97 kDa and 27.33 kDa, respectively. The genomic sequence analysis showed SmDHAR1 and SmDHAR2 contained five and six introns, respectively. Reverse transcription PCR revealed that the SmDHAR1 and SmDHAR2 were constitutive expression genes in S. moellendorffii. The recombinant SmDHAR1 and SmDHAR2 proteins were overexpressed in E. coli, and were purified by Ni-affinity chromatography. The recombinant SmDHAR1 showed 116-fold higher enzymatic activity towards the substrate dehydroascorbate than recombinant SmDHAR2. The recombinant SmDHAR1 showed higher thermal stability than recombinant SmDHAR2. These results indicated obvious functional divergence between the duplicate genes SmDHAR1 and SmDHAR2.

Trehalose-6-phosphate synthase, a key enzyme in trehalose synthesis pathway of plant, plays an important role in response to abiotic stress in xerophilous rock lily and other resurrection plants. In this study, homologous amplification and RACE technique were used to clone gene SpTPS1 for trehalose-6-phosphate synthase from Selaginella pulvinata, which is an endemic xerophilous plant in China. The full-length cDNA is 3223 bp long, containing an open reading frame (ORF) of 2790 bp. Protein sequence comparison showed that the pupative amino acid sequence of this ORF shares high similarity to trehalose-6-phosphate synthases of mode species, especially at the conserved sites of catalytic activity centers. Yeast functional complementation test showed that trehalose-6-phosphate synthase mutant (tps1 big up tri, open), transformed by the ORF of SpTPS1 gene, can restore growth on the medium supplemented with glucose as a sole carbon source. This result indicated that SpTPS1 of S. pulvinata encodes for an active protein and is hopeful to be applied in transgenic improvement of abiotic stress tolerance in plant.