AUTHOR=Jing Xiaoshu , Hou Peichen , Lu Yanjun , Deng Shurong , Li Niya , Zhao Rui , Sun Jian , Wang Yang , Han Yansha , Lang Tao , Ding Mingquan , Shen Xin , Chen Shaoliang TITLE=Overexpression of copper/zinc superoxide dismutase from mangrove Kandelia candel in tobacco enhances salinity tolerance by the reduction of reactive oxygen species in chloroplast JOURNAL=Frontiers in Plant Science VOLUME=6 YEAR=2015 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00023 DOI=10.3389/fpls.2015.00023 ISSN=1664-462X ABSTRACT=

Na+ uptake and transport in Kandelia candel and antioxidative defense were investigated under rising NaCl stress from 100 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 day. 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.