Effect of exogenous melatonin on cold resistance of Brassica rapa seedlings under low temperature stress
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DOI:10.7606/j.issn.1000-7601.2019.04.22
Key Words: Brassica rapa  melatonin  low temperature stress  antioxidant enzyme  MAPKs gene expression
Author NameAffiliation
SHI Zhong-fei School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
LIANG Juan-hong School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
ZHANG Xiao-hua School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
CHENG Hong-bing School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
ZHENG Sheng School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
WANG Juan School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
ZHANG Teng-guo School of Life Sciences, Northwest Normal University, Lanzhou, Gansu 730070,China 
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Abstract:
      The objective of this study was to investigate the effects of melatonin (MT) on the resistance of Brassica rape seedlings under low temperature stress. In this study, Brassica rapa “Longyou 6” was used as experimental material. The effects of exogenous MT on the relative conductivity, chlorophyll content, ROS content, antioxidant enzyme activity, and the expression of MAPK3, MAPK4, and MAPK6 genes of leaves in Brassica rape under low temperature stress were investigated. The results showed that compared with 4 ℃ stress treatment alone, under 100 μmol·L-1 MT pretreatment then treated with low temperature stress for different time (12, 24, 36, 48 h), the MDA content, relative conductivity and ROS content in Brassica rapa seedlings significantly decreased, MDA and relative conductivity were reduced by 14.3%, 15.0%, 17.2%, 20.0% and 11.5%, 12.8%, 16.2%, 15.1%, respectively, but chlorophyll content, three antioxidant enzyme activities (CAT, POD, SOD) and MAPK3, MAPK4, MAPK6 genes expression all increased by low temperature stress, the activity of CAT increased by 28.5%, 23.1%, 7.6%, and 13.1%, respectively, and the activities of POD and SOD increased by 36.0%, 25.3%, 5.9%, 18.7%, and 14.6%, 18.6%, 9.1%, 13.6%, respectively. So, we concluded that 100 μmol·L-1 exogenous MT pretreatment could significantly decreased the MDA content, reactive oxygen species (ROS) level, and electrolyte leakage, but increased chlorophyll content and activities of antioxidate system enzymes (CAT, POD and SOD), as induced MAPK3, MAPK4, and MAPK6 gene expression, decreased the membrane lipid peroxidation, maintained membrane integrity, and improved the adaptability of Brassica rape seedlings under low temperature stress.
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