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=<p>Na<sup>+</sup> uptake and transport in <italic>Kandelia candel</italic> and antioxidative defense were investigated under rising NaCl stress from 100 to 300 mM. Salinized <italic>K. candel</italic> roots had a net Na<sup>+</sup> efflux with a declined flux rate during an extended NaCl exposure. Na<sup>+</sup> buildup in leaves enhanced H<sub>2</sub>O<sub>2</sub> levels, superoxide dismutase (SOD) activity, and increased transcription of <italic>CSD</italic> 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. <italic>KcCSD</italic>-transgenic lines were more Na<sup>+</sup> 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 <italic>a</italic> fluorescence, and photochemical efficiency of photosystem II. NaCl stress in WT resulted from H<sub>2</sub>O<sub>2</sub> burst in chloroplast. Na<sup>+</sup> injury to chloroplast was less pronounced in <italic>KcCSD</italic>-transgenic plants due to upregulated antioxidant defense. <italic>KcCSD</italic>-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 <italic>KcCSD</italic> overexpressing tobacco plants. <italic>KcCSD</italic>-transgenic plants better scavenged NaCl-elicited reactive oxygen species (ROS) compared to WT ones. In conclusion, <italic>K. candel</italic> effectively excluded Na<sup>+</sup> in roots during a short exposure; and increased <italic>CSD</italic> expression to reduce ROS in chloroplast in a long-term and high saline environment.</p>