Correlation Between Polysaccharides Accumulation And Sugar Metabolism In Dendrobium Officinale

Dendrobium officinale Kimura et Migo is a rare traditional medicinal herb, polysaccharide is the main effect component also the judgment standard of its quality. Sucrose is a precursor of polysaccharide, so research the mechanism of polysaccharide accumulation and sucrose metabolism has a great significance for production improve and quality breeding. By physiological, biochemical and molecular biology methods, measure the sugar content, activity and expression of sucrose-metabolizing enzymes of D. officinale which fom the tissue culture and field cultivation.The relationship between polysaccharide accumulation and sucrose metabolism was preliminary concluded. Then by regulating the sucrose concentration of medium to explore polysaccharide improving approach.The mian results were as follows:By researching the D. officinale tissue culture with different culture time(3 months, 5 months, 7 months), the results showed that: Polysaccharides, glucose, sucrose and reducing sugar content showed a gradual increasing trend with the growth over time, while the fructose content decrease gradually. During the growth,the proportion of reducing sugar to sucrose continue to decrease,that means at early growth stage the reducing sugar was the main accumulation, later is the stage of sucrose accumulation. Glucose, sucrose, polysaccharide were significantly positively correlated to each other.Sucrose Phosphate Synthase(SPS) and Sucrose Synthase(SS) works together for the synthesis of sucrose, SPS is more important than SS. Acid Invertase(AI) is the main enzyme responsible for sucrose decomposition. SS and SPShave a higher expression in leaves than in the stems,which means leaves are the mian site for sucrose synthesis.Alkaline Invertase(NI) has a low level and changes little in the growth stage.The correlation coefficient of polysaccharide content and AI activity reaching a significant level in tissue culture(R = 0.830,P<0.05).Through the study of two D. officinale species(78 × 69,6A × 2B) collected at different period(July, December, April), the results showed that: two species of D. officinale has a similar change trend with sugar and sucrose metabolizing enzymes. Stem polysaccharide content increased gradually,while the polysaccharide in the leaves decreased at December and then increased at April of the next year.The activity of SS,SPS and AI also increased first and then decreased. That is due to low temperature in December, D. officinale ease the low temperature damage by increasing the activity of AI,SPS,SS to increase soluble sugar content.With the treatment of different concentrations of sucrose(20g/L, 35g/L, 50g/L) and different culture time(2 months, 4 months, 6 months) on C27, research the polysaccharide accumulation and sucrose metabolism under different sucrose concentration. The results show that: under 4 months treatment, there were a significant differences of stem polysaccharide among the three treatment, and polysaccharide content and biomass yield increased simultaneously with sucrose concentration increasing.The content of reducing sugar and sucrose increased simultaneously with sucrose concentration increasing, also AI and SS activity increased gradually. The correlation coefficient of polysaccharide content and AI activity reaching a significant level in tissue culture(R = 0.856,P<0.05).The correlation coefficient of sucrose content and SPS also SS activity reaching a significant level.