Abstract
Membrane lipid alterations affect Al tolerance in plants, but little is known about the regulation of membrane lipid metabolism in response to Al stress. Transgenic tobacco (Nicotiana tabacum) overexpressing rice monogalactosyldiacylglycerol (MGDG) synthase (OsMGD) gene and wild-type tobacco plants were exposed to AlCl3, and the impact of Al toxicity on root growth, Al accumulation, plasma membrane integrity, lipid peroxidation and membrane lipid composition were investigated. Compared with the wild type, the transgenic plants exhibited rapid regrowth of roots after removal of Al and less damage to membrane integrity and lipid peroxidation under Al stress, meanwhile, the Al accumulation showed no difference between wild-type and transgenic plants. Lipid analysis showed that Al treatment dramatically decreased the content of MGDG and the ratio of MGDG to digalactosyldiacylglycerol (DGDG) in wild-type plants, while it was unchanged in transgenic plants. The stable of MGDG level and the ratio of MGDG/DGDG contribute to maintain the membrane stability and permeability. Moreover, Al caused a significant increase in phospholipids in wild-type plants, resulting in a high proportion of phospholipids and low proportion of galactolipids, but these proportions were unaffected in transgenic plants. The high proportion of phospholipids could contribute to a higher rate of Al3+ binding in the membrane and thereby leads to more membrane perturbation and damage. These results show that the regulation of galactolipid biosynthesis could play an important role in maintaining membrane structure and function under Al stress.
Highlights
Aluminum (Al) is the most abundant metal in the earth’s crust and is a major factor limiting plant production in acid soils, which cover about 50% of the world’s potentially arable land surface (Kochian et al, 2004; Liu et al, 2014)
Inhibition of root growth is the primary symptom of Al toxicity which has been widely accepted as a suitable indicator for assessing Al tolerance in plants (Delhaize and Ryan, 1995; Ezaki et al, 2000; Tahara et al, 2008; Yin et al, 2010a,b)
Al compared with the wild type (Figure 1), indicating that Al tolerance was enhanced in transgenic plants
Summary
Aluminum (Al) is the most abundant metal in the earth’s crust and is a major factor limiting plant production in acid soils, which cover about 50% of the world’s potentially arable land surface (Kochian et al, 2004; Liu et al, 2014). Cell membranes are vital because they separate the cell from its surrounding environment and enable cellular activities to proceed without external interference. They are damaged by various environmental stresses, including Al stress. Lipids are the predominant constituent of cell membranes, and changes in membrane lipid composition have frequently been found under various environmental stress conditions, such as cold, drought and salinity; these changes are thought to contribute to the restoration and maintenance of membrane stability and integrity, and to increase plant stress tolerance (Campos et al, 2003; Gigon et al, 2004; Bybordi, 2011). Our group has found that increased the biosynthesis of MGDG contributes to maintain the membrane structure and function of chloroplast, and leads to enhanced salt tolerance (Wang et al, 2014)
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