Project description:Dendrobium catenatum (D. catenatum) has long been used as an important medicinal herb in oriental medicine. Polysaccharide, flavonoid, and alkaloid are the major active ingredients, the production and accumulation of which are frequently affected by many environmental factors including water, temperature, and mycorrhizal fungus. However, how phytohormones frequently used in orchid tissue culture regulate the production of active components in D. catenatum is far from clear. Here, major medicinal metabolites were comparatively analyzed in 2-month-old D. catenatum seedlings exposed to phytohormones (0.1 mg/L NAA and/or 1.0 mg/L 6-BA) for three weeks, and eight transcriptomes (two replicates each) corresponding to the treatments were generated. Results demonstrated that the phytohormones triggered transcriptional reprograming, analysis of which revealed a tight association of β-glucosidase (BGLU) expression with the accumulation of polysaccharide. Subsequently, a second RNA-sequencing was further conducted to reveal that a relatively short period (2 w) of varied concentrations of 6-BA application might initially reduce BGLU expression and polysaccharide content and then increase their levels with prolonged treatments (4 w). The RNA-seq data was reconfirmed by functional analysis that 6-BA induced polysaccharide production, while knockdown of BGLU2L resulted in decreased polysaccharide levels. Therefore, the present study clearly demonstrated that BGLU is a key regulator for polysaccharide production and that it is extremely susceptible to NAA and 6-BA treatments in D. catenatum.
