Phytohormone-triggered Transcriptional ChangesRevealed?-Glucosidaseas a Key Player forPolysaccharide Metabolism in Dendrobium officinale br

ObjectiveDendrobium officinalehas 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 frequentlyaffected by numerous environmental cues.Phytohormone supplemented in culture medium has facilitated the mass production oforchids.However,their mechanism of action on the production of active components inDendrobium officinaleis far from clear.MethodsHere,major medicinal metabolites were comparatively analyzed inDendrobium officinaleseedlings exposed to the mostcommonly used phytohormones(NAA and/or6-BA),and transcriptomes corresponding to the treatments were generated.ResultsResults showed that phytohormones greatly affected the accumulation of polysaccharide,alkaloid,and flavonoid,andtriggered tremendous transcriptional changes.It was demonstrated that6-BA induced more transcripts than NAA and that beta-glucosidase(BGLU)expression was closely related to polysaccharide production.Further functional analysis revealed that factorsincluding phytohormone category,concentration,treating duration,and seedling growth stages,can drastically affect theBGLUexpression and the corresponding polysaccharide production,thus partially answered the key question at molecular level why themedicinal constituents are unstable in tissue culture derivedDendrobiumplants.ConclusionAltogether,the present study clearlydemonstrated thatBGLUis a key regulator for polysaccharide production inDendrobium officinalein response to phytohormonetreatments.