Effects of antimony on synthesis of saccharides and lipids, and enzyme activity associated with synthesis/degradation of saccharides in leaves of a rice plant

Different forms of antimony (Sb) show different toxicities to plants, which are hypothesized to be partially due to the disorders of lipid and saccharide synthesis. Hydroponic experiments were conducted using a rice plant (Yangdao 6) exposed to antimonite (Sb(III)) and antimonate (Sb(V)). We monitored the following (1) saccharide concentration and enzymatic activities associated with synthesis/degradation of sucrose and starch; (2) changes in cell ultrastructure of rice leaves; and (3) differentially expressed metabolites (DEMs) associated with lipids. The results showed that when compared to the control, Sb(III/V) (1) increased the concentrations of starch, soluble sugars, sucrose and fructose as well as the activities of cell–wall binding acid invertase (B–AI) in rice leaves; (2) mainly affected the abundance of unsaturated lipids of fatty acids (FAs), prenol lipids, glycerolipids, and glycerophospholipids, especially for Sb(III); and (3) negatively affected the abundance of DEMs associated with α–linolenic acid metabolism and xanthophyll formation. Relative to Sb(V), Sb(III) (1) showed great negative effects on the activities of fructose–1, 6–diphosphatase (FBP), triose–phosphate isomerase (TPI), α–glucosidase, and sucrose–phosphate synthase (SPS); (2) significantly narrowed the shape of starch granules and increased the thickness of cell walls; (3) increased numbers and abundance of DEMs associated with toxins (belonging to sphingolipids), flavonoids (polyketides), and biomarkers (corticosteroid hormones); and (4) increased the numbers of FAs whose abundance was upregulated. This study showed a complex regulatory network associated with saccharide synthesis/degradation and lipid constitution in response to Sb toxicity.