Change of Antioxidant Enzyme Activity during Low-Temperature Hardening of Nicotiana tabacum L. and Secale cereale L.

Abstract

Changes in the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) for the plants Nicotiana tabacum L. and Secale cereale L. during low-temperature hardening have been investigated. It was determined that a transient increase in the content of MDA occurs in tobacco plants at the beginning of the hardening period with subsequent activation of SOD, APX, and CAT. Unlike tobacco, winter rye has an MDA content and activity of SOD, APX, and CAT throughout the hardening period that remains at the level of unhardened plants. In tobacco cells, the majority of SOD activity was detected in chloroplasts (90%), while other cellular structures accounted for only 10% of the total activity identified in PAGE. In winter rye cells, SOD activity was distributed evenly between chloroplasts and other cellular compartments (46% in chloroplasts and 54% outside of chloroplasts). The distribution of APX and CAT activity in tobacco and winter rye cells was identical: all APX was concentrated in chloroplasts, while all catalase activity was manifested outside of chloroplasts. It is concluded that tobacco and winter rye plants showed different antioxidant defense strategies under conditions of low hardening temperatures. Tobacco plants provided protection against oxidative damage during low-temperature hardening by increasing activity of SOD, APX, and CAT. Winter rye plants were able to avoid the development of oxidative stress during hardening due to uniform distribution of SOD activity in cells, maintaining the constitutive activity of SOD, APX, and CAT, and, probably, due to the accumulation of nonenzymatic antioxidants.