Overexpression of copper/zinc superoxide dismutase from mangrove Kandelia candel in tobacco enhances salinity tolerance by the reduction of reactive oxygen species in chloroplast

• Main Authors: Xiaoshu eJing, Peichen eHou, Yanjun eLu, Shurong eDeng, Niya eLi, Rui eZhao, Jian eSun, Yang eWang, Yansha eHan, Tao eLang, Mingquan eDing, Xin eShen, Shaoliang eChen
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2015-01-01
• Series: Frontiers in Plant Science
• Subjects: Catalase; Hydrogen Peroxide; Superoxide Dismutase; salt; Superoxide anion; Kandelia candel
• Online Access: http://journal.frontiersin.org/Journal/10.3389/fpls.2015.00023/full

Na+ uptake and transport in Kandelia candel and antioxidative defense were investigated under rising NaCl stress from 100 mM to 300 mM. Salinized K. candel roots had a net Na+ efflux with a declined flux rate during an extended NaCl exposure. Na+ buildup in leaves enhanced H2O2 levels, superoxide dismutase (SOD) activity, and increased transcription of CSD gene encoding a Cu/Zn SOD. Sequence and subcellular localization analyses have revealed that KcCSD is a typical Cu/Zn SOD in chloroplast. The transgenic tobacco experimental system was used as a functional genetics model to test the effect of KcCSD on salinity tolerance. KcCSD-transgenic lines were more Na+ tolerant than wild-type (WT) tobacco in terms of lipid peroxidation, root growth, and survival rate. In the latter, 100 mM NaCl led to a remarkable reduction in chlorophyll content and a/b ratio, decreased maximal chlorophyll a fluorescence, and photochemical efficiency of photosystem II. NaCl stress in WT resulted from H2O2 burst in chloroplast. Na+ injury to chloroplast was less pronounced in KcCSD-transgenic plants due to upregulated antioxidant defense. KcCSD-transgenic tobacco enhanced SOD activity by an increment in SOD isoenzymes under 100 mM NaCl stress from 24 h to 7 d. Catalase activity rose in KcCSD overexpressing tobacco plants. KcCSD-transgenic plants better scavenged NaCl-elicited reactive oxygen species (ROS) compared to WT ones. In conclusion, K. candel effectively excluded Na+ in roots during a short exposure; and increased CSD expression to reduce ROS in chloroplast in a long-term and high saline environment.