Maintenance of Chloroplast Structure and Function by Overexpression of the Rice MONOGALACTOSYLDIACYLGLYCEROL SYNTHASE Gene Leads to Enhanced Salt Tolerance in Tobacco

Shiwen Wang; M Imtiaz Uddin; Kiyoshi Tanaka; Lina Yin; Zhonghui Shi; Yanhua Qi; Jun'ichi Mano; Kenji Matsui; Norihiro Shimomura; Takeshi Sakaki; Xiping Deng; Suiqi Zhang

doi:10.1104/pp.114.238899

Maintenance of Chloroplast Structure and Function by Overexpression of the Rice MONOGALACTOSYLDIACYLGLYCEROL SYNTHASE Gene Leads to Enhanced Salt Tolerance in Tobacco

Plant Physiol. 2014 Jul;165(3):1144-1155. doi: 10.1104/pp.114.238899. Epub 2014 May 19.

Authors

Affiliations

¹ State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China (S.W., L.Y., Z.S., X.D., S.Z.);Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China (S.W., L.Y., X.D., S.Z.);Faculty of Agriculture, Tottori University, Tottori 680-8533, Japan (M.I.U., K.T., L.Y., N.S.);State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China (Y.Q.);Science Research Center (J.M.) and Department of Biological Chemistry, Faculty of Agriculture, and Department of Applied Molecular Bioscience, Graduate School of Medicine (K.M.), Yamaguchi University, Yamaguchi 753-8515, Japan; andDepartment of Biology, School of Biological Science, Tokai University, Minami-ku, Sapporo 005-8601, Japan (T.S.).
² State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China (S.W., L.Y., Z.S., X.D., S.Z.);Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China (S.W., L.Y., X.D., S.Z.);Faculty of Agriculture, Tottori University, Tottori 680-8533, Japan (M.I.U., K.T., L.Y., N.S.);State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China (Y.Q.);Science Research Center (J.M.) and Department of Biological Chemistry, Faculty of Agriculture, and Department of Applied Molecular Bioscience, Graduate School of Medicine (K.M.), Yamaguchi University, Yamaguchi 753-8515, Japan; andDepartment of Biology, School of Biological Science, Tokai University, Minami-ku, Sapporo 005-8601, Japan (T.S.) linayin@nwsuaf.edu.cn.

Abstract

In plants, the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactodiacylglycerol (DGDG) are major constituents of photosynthetic membranes in chloroplasts. One of the key enzymes for the biosynthesis of these galactolipids is MGDG synthase (MGD). To investigate the role of MGD in the plant's response to salt stress, we cloned an MGD gene from rice (Oryza sativa) and generated tobacco (Nicotiana tabacum) plants overexpressing OsMGD. The MGD activity in OsMGD transgenic plants was confirmed to be higher than that in the wild-type tobacco cultivar SR1. Immunoblot analysis indicated that OsMGD was enriched in the outer envelope membrane of the tobacco chloroplast. Under salt stress, the transgenic plants exhibited rapid shoot growth and high photosynthetic rate as compared with the wild type. Transmission electron microscopy observation showed that the chloroplasts from salt-stressed transgenic plants had well-developed thylakoid membranes and properly stacked grana lamellae, whereas the chloroplasts from salt-stressed wild-type plants were fairly disorganized and had large membrane-free areas. Under salt stress, the transgenic plants also maintained higher chlorophyll levels. Lipid composition analysis showed that leaves of transgenic plants consistently contained significantly higher MGDG (including 18:3-16:3 and 18:3-18:3 species) and DGDG (including 18:3-16:3, 18:3-16:0, and 18:3-18:3 species) contents and higher DGDG-MGDG ratios than the wild type did under both control and salt stress conditions. These results show that overexpression of OsMGD improves salt tolerance in tobacco and that the galactolipids MGDG and DGDG play an important role in the regulation of chloroplast structure and function in the plant salt stress response.