Waterlogging Influences Plant Growth and Activities of Superoxide Dismutases in Narrow-leafed Lupin and Transgenic Tobacco Plants

The effects of waterlogging on plant growth and activities of superoxide dismutase (SOD) forms were studied in seedlings of narrow-leafed lupin (Lupinus angustifolius L.) and transgenic tobacco (Nicotiana tabacum L.) plants engineered to overproduce MnSOD or FeSOD in chloroplasts. Waterlogging for 2 days decreased shoot elongation rate by 57% in lupins, and with prolonged waterlogging (4 days) soluble protein concentration declined significantly; however, shoot dry weight was not affected during the whole course of waterlogging stress. After 2 days of recovery (by draining excess water in treatment pots), shoot dry weight was reduced slightly but significantly, while shoot elongation rate and protein concentration continued to decline. The activities of FeSOD and Cu/ZnSOD increased constantly during waterlogging and recovery periods, while those of total SOD and MnSOD decreased initially and increased afterwards.Growth of transgenic tobacco was not affected after 2 days of waterlogging, while non-transgenic parental line showed decreased growth at this stage. Following 2 days of recovery, growth was significantly reduced in all lines, bur transgenics suffered proportionally smaller growth reduction than did non-transgenics. This result corresponded with the higher activity of MnSOD or FeSOD in transgenic lines compared to the non-transgenic parent. It is concluded that overproduction of FeSOD or MnSOD in transgenic tobacco enables plants to better tolerate waterlogging-induced oxidative stress and maintain growth rate under stress conditions compared to non-transgenic parent; therefore, engineering lupins for overproduction of FeSOD or MnSOD to increase tolerance to waterlogging stress is warranted.