Physiological And Protemic Study Of Sargassum Fusifoeme Under Hypotonic Stress

The intertidal marine macroalgae Sargassum fusiforme show remarkable tolerances to freshwater immersion.Experienced cultivators find that immersion of S.fusiforme in freshwater for 1 hour can effectively remove harmful epiphytic plants and animals.Here,Biochemical and physiological analysis and comparative proteomics were performed to investigate the molecular mechanisms of hypotonic-stress-tolerance in S.fusiforme.Our results showed that in the initial period of freshwater immersion,inorganic anion may be lost much faster than other soluble contents.H2O2 accumulation occurred immediately and the antioxidant system was efficiently activated during freshwater immersion.Moreover,it was also showed that freshwater immersion induced spontaneous accumulation of H2O2 firstly occurred in chloroplast,then in cytosols and peroxisomes.Fifth-one proteins were significant differentially expressed during freshwater immersion that were identified by comparative proteomic analysis,with 9 up-regulated and 42 down-regulated,most of which were enzymesinvolved in photosynthesis,carbohydrate metabolism and energy metabolism.In conclusion,one-hour's-freshwater-immersion negatively affected the metabolic activity of S.fusiforme,as most key metabolic enzymes were down-regulated.As a fundamental work for algae under abiotic stress,analyzing the effects of freshwater immersion on the brown seaweeds,S.fusiforme,would help revealing the mechanisms of their hypotonic tolerance,together providing theoretical basis for the 'freshwater pesticide' technology.