Overexpression of S-adenosylmethionine synthetase gene enhances polyamine content and antioxidant activity in transgenic plants

The interaction between polyamine content and antioxidant activity in plants can confer resistance to environmental stress. In this study, polyamines and antioxidant activities in T₂-generation transgenic plants overexpressing the MsSAMS (Miscanthus sinensis S-adenosylmethionine synthetase) gene were studied. First, the results of plant length, leaf length, leaf width, leaf number, stem diameter, and chlorophyll content in the T₂-generation transgenic plants into which the MsSAMS gene was inserted showed that there were only slight differences in the agricultural phenotype, and no significant difference was observed. Result of the analyses of polyamine-based components: putrescine, spermidine, and spermine showed that there was no detectable amount of putrescine in the control group, whereas in the T6 line, it was 399.14 ± 15.46 μg/g FW. Spermidine level was 1497.16 ± 53.28 μg/g FW and 146.97 ± 12.58 μg/g FW in the T17 and T9 lines of transgenic plants, respectively. Furthermore, free radical scavenging activity was measured using DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid)] assays. T17 line showed the highest antioxidant activity (1974.85 ± 18.06 μg/mL) in DPPH assay, whereas T6 line showed the highest activity (7390.12 ± 67.39 μg/mL) in ABTS assay. Results of the analysis of the total phenol and flavonoid content of the transgenic plants revealed that the T6 line and T2 line showed the highest values, respectively (208.20 ± 3.36 mg GAE/g and 22.07 ± 0.49 mg QE/g, respectively). These results suggest that the MsSAMS gene plays a role in enhancing antioxidant activity by increasing polyamine content.