Characterization of Cu/Zn-SOD enzyme activities and gene expression in soybean under low nitrogen stress

Superoxide dismutase (SOD) plays an important role in antioxidant defense in nearly all cells, and is speculated to be closely related to plant resistance to biotic and abiotic stresses, such as drought, salt, heavy metal and pathogen attack. However, little is known about the effects of SOD activity and its isoenzymes on low nitrogen stress tolerance and its effects on adaptability of plants to nitrogen limitation.Ten SOD isoenzymes were identified in soybean root, stem, leaf and mature seed, and were classified into three families (α.1, β.1-4 and γ.1-5). SOD activity was significantly elevated in soybean leaf and root. Conversely, under low-nitrogen conditions, only β.2 isoenzyme activity, belonging to the Cu/Zn-SOD family, was induced obviously in the root of soybean cultivar cv. WS01-15. Moreover, the expression of three Cu/Zn-SOD genes was analyzed under low nitrogen stress. GmCZ-SOD1 gene was induced significantly in soybean root under low nitrogen stress. Interestingly, evolutionary analysis showed that this gene underwent a strong artificial selection during soybean domestication, suggesting that the Cu/Zn-SOD gene plays an essential role in the adaptive evolution of soybean nitrogen limitation resistance.GmCZ-SOD is important for adaptability of soybean to nitrogen limitation and these results provide useful information to unravel its biological role in low nitrogen resistance in plants. © 2015 Society of Chemical Industry.