植物激素处理诱导的转录组改变揭示铁皮石斛β葡糖苷酶在多糖合成中的关键作用

Phytohormone-triggered Transcriptional Changes Revealedβ-Glucosidase as a Key Player for Polysaccharide Metabolism in Dendrobium officinale

目的铁皮石斛是一种名贵的中草药,药用历史悠久,其药用活性成分主要包括多糖、类黄酮和生物碱。这些成分的种类和含量通常受到诸多环境因素的影响。组织培养中植物激素的广泛使用促进了许多兰科植物的大量快繁,然而植物激素对活性成分积累的影响及其作用机制尚待进一步深入研究。方法本文利用铁皮石斛组织培养常用的两种植物激素NAA和(/或)6-BA处理铁皮石斛幼苗,测定活性化合物含量并对相应材料进行转录组测序分析。结果激素处理影响多糖、生物碱和类黄酮等活性化合物的积累水平,同时引起较多的差异基因表达。统计分析表明,6-BA较NAA处理引起更多的转录本改变,β葡糖苷酶编码基因BGLU表达与多糖积累密切相关。进一步功能研究表明,包括激素种类、处理浓度、处理时间和处理材料生长时期等因素均能明显影响BGLU表达及相应多糖积累水平,从而在分子层面部分回答了一个长期困扰人们的关键问题,即为什么药材经组织培养后活性成分相对不稳定。结论本研究明确提出了BGLU在激素处理后多糖的积累过程中有重要调控作用。

Objective Dendrobium officinale 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 numerous environmental cues.Phytohormone supplemented in culture medium has facilitated the mass production of orchids.However,their mechanism of action on the production of active components in Dendrobium officinale is far from clear.Methods Here,major medicinal metabolites were comparatively analyzed in Dendrobium officinale seedlings exposed to the most commonly used phytohormones(NAA and/or 6-BA),and transcriptomes corresponding to the treatments were generated.Results Results showed that phytohormones greatly affected the accumulation of polysaccharide,alkaloid,and flavonoid,and triggered tremendous transcriptional changes.It was demonstrated that 6-BA induced more transcripts than NAA and thatβ-glucosidase(BGLU)expression was closely related to polysaccharide production.Further functional analysis revealed that factors including phytohormone category,concentration,treating duration,and seedling growth stages,can drastically affect the BGLU expression and the corresponding polysaccharide production,thus partially answered the key question at molecular level why the medicinal constituents are unstable in tissue culture derived Dendrobium plants.Conclusion Altogether,the present study clearly demonstrated that BGLU is a key regulator for polysaccharide production in Dendrobium officinale in response to phytohormone treatments.