Study On Cell Growth And Polysaccharide Production Regulated By Rare Earth Elements In Suspension Cultures Of Protocorm-like Bodies From Dendrobium Huoshanense

Dendrobium Huoshanense, an endangered plant, has been used in traditional Chinese medicine for centuries. Modern pharmacological studies have proved that Dendrobium huoshanense has good potential for anti-oxidation,immunomodulating, anti-tumor and anti-cataract functions and the pharmacological effects are related to the content of polysaccharides. Recent references indicate that rare earth elements are one of the most important elicitors to regulate cell growth and metabolite biosynthesis and the studies were focused on the production of secondary metabolites in plant cell cultures. To our best knowledge, the effects of fare earth elements on polysaccharide synthesis in plant cell culture were rarely reported.Improved MS culture medium was chosen to investigate the effects of rare earth elements on cell growth, accumulation of polysaccharides, utilization of nutrient together with phosphorus and pH in medium from protocorm-like bodies (PLBs) of Dendrobium huoshanense in this paper. The results indicated that La³⁺in the tested concentrations did not improve PLB growth and polysaccharide synthesis. However, PLB growth and polysaccharide accumulation could be enhanced by Ce³⁺ and Nd³⁺ at the concentration from 5.0μmol/L to 40.0μmol/L. As far as polysaccharide production is concerned, the highest value of 3,35 g/L and 3.41 g/L were obtained on the day 18^th during culture period by 10.0μmol/L Ce³⁺ and Nd³⁺, respectively, which were 50% higher than control. With respect to PLB growth, the peaks of cell dry weight were observed on the day 24^th during culture period, which were 15% higher than control. In addition, the possible mechanisms of enhancement of PLB growth and polysaccharide synthesis by rare earth elements were analyzed from the aspects of carbon and nitrogen metabolism. Results showed that the regulation of PLB growth and polysaccharide accumulation by Ce³⁺ and Nd³⁺ might be very related to the key enzyme expressions of invertase and sucrose synthase in carbon metabolism as well as to the other enzymes in nitrogen metabolism.The results showed that rare earth elements added to the medium can adjust PLB growth and polysaccharide synthesis, and can significantly enhance polysaccharide production, which will supply the guidance for polysaccharide production in large-scale culture of PLBs of Dendrobium huoshanense.