Abstract

Alkaline/neutral invertase is one of the key enzymes in sucrose metabolism, which irreversibly converts sucrose into fructose and glucose, the precursors of polysaccharide synthesis. Our main objective is to study the alkaline/neutral invertase gene function of Dendrobium catenatum, a rare and endangered medicinal plant, and provide evidence for revealing the biosynthesis of polysaccharides in Dendrobium catenatum. Eight alkaline/neutral invertase genes were identified from Dendrobium catenatum genome and DcNI4 gene was found to be highly expressed in stem by transcriptomic data, which was consistent with the high polysaccharide content in stem of Dendrobium catenatum. DcNI4 was confirmed to localize in cytoplasm. The expression level of DcNI4 in stem was significantly higher than that in roots and leaves at 6 mo, this difference might be due to the accumulation of polysaccharides and the energy consumption of plant growth. In Arabidopsis thaliana, DcNI4-overexpressing types had higher DcNI4 activity, increased polysaccharide content and promoted the root development. Our results provide new insights into the biological function of DcNI4 and lay a foundation for analysing the synthesis pathway of polysaccharides in Dendrobium catenatum.