Antioxidant metabolic system and comparative proteomics analysis in winter turnip rape (Brassica rapa L.) under cold stress

Winter turnip rape (Brassica rapa L.) is widely cultivated in winter in Northwest China, however, its cold-tolerant mechanism remains insufficiently understood. In this study, winter turnip rape cultivar Longyou 7, a cold-tolerant variety, was used as material, whose accumulation of H₂O₂ and O₂^•-, antioxidant enzyme activity as well as differences in protein expression based on two-dimensional gel electrophoresis (2-DE) technique under −4°C stress were analyzed. Results showed that, production of H₂O₂ and O₂^•- were increased in Longyou 7 leaves, simultaneously, SOD and POD activities were also obviously rosed up, but the activities of CAT and APX were gradually reduced with the temperature. Thirty-six differential protein spots were successfully identified between control and treatments group by using mass spectrometry analysis. Among them, 4 differential protein spots were induced under cold stress, and 2 were inhibited at −4°C. Functional analysis found that these identified proteins mainly participated in photosynthesis, carbohydrate metabolism, defense, protein synthesis, enzyme activity, redox and membrane metabolism, respectively. Additionally, 13 proteins' function were still unknown. In conclusion, strong antioxidant capacity and cell defense ability might play important roles in Longyou 7 response to cold stress.