Dendrobium officinale is an economically important Chinese herb with ornamental and medicinal values. However, the mechanisms by which D. officinale adapts to cadmium (Cd) stress is unknown. Here, physiological changes in D. officinale roots and leaves exposed to increasing levels of Cd stress (CdSO4 concentration of 2, 5, 9, 14 mg L-1) were analyzed at 7, 15, 30, and 45 days after treatment. The Cd stress of 14 mg L-1 significantly increased the levels of antioxidants and induced malondialdehyde and proline accumulation (P < 0.05). Cd subcellular distribution showed that Cd sequestration into soluble fraction is the major detoxification mechanism in D. officinale roots. Subsequently, the transcriptome profile of D. officinale roots treated with 14 mg L-1 Cd for 15 and 30 days was analyzed. Compared to control, 2,469 differentially expressed genes (DEGs) were identified, comprising 1,486 up-regulated genes and 983 down-regulated genes. The DEGs associated with metabolic pathways for Cd uptake, transportation and detoxification were analyzed. Several processes such as metal transporter, sulfate glutathione metabolism, cell wall metabolism, phenylpropanoid metabolism were identified to be important for Cd stress adaptation. More genes were expressed at 15 days after treatment compared to 30 days. WRKY, Trihelix, NF-YC, MYB, bZIP and bHLH transcription factors were over-expressed at both time points. Furthermore, candidate genes from the glutathione metabolism pathway were identified, and qRT-PCR analysis of ten DEGs indicated a high coorelation with RNA-seq expression profiles. Our findings provide significant information for further research of Cd stress responsive genes functions in D. officinale, especially the genes from the glutathione metabolism pathway.

中文翻译：

---

铁皮石seedling幼苗中镉胁迫响应的生理和转录组学分析。

铁皮石end是具有观赏和药用价值的经济上重要的中草药。但是，D。officinale适应镉（Cd）胁迫的机制尚不清楚。在这里，在处理后第7、15、30和45天分析了不断增加的Cd胁迫（CdSO4浓度为2、5、9、14 mg L-1）下的D. officinale根和叶的生理变化。14 mg L-1的镉胁迫显着增加了抗氧化剂的水平，并诱导了丙二醛和脯氨酸的积累（P <0.05）。Cd亚细胞分布表明，Cd螯合为可溶性级分是D.officinale根的主要解毒机理。随后，分析了用14 mg L-1 Cd处理15天和30天的石竹根的转录组概况。与对照相比，2 鉴定了469个差异表达基因（DEG），包括1,486个上调基因和983个下调基因。分析了与Cd吸收，运输和排毒的代谢途径相关的DEG。几个过程，如金属转运蛋白，硫酸盐谷胱甘肽代谢，细胞壁代谢，苯丙氨酸代谢被确定对Cd应力适应很重要。与30天相比，在治疗后15天表达的基因更多。WRKY，Trihelix，NF-YC，MYB，bZIP和bHLH转录因子在两个时间点均过表达。此外，从谷胱甘肽代谢途径中鉴定出候选基因，并且对十个DEG的qRT-PCR分析表明与RNA-seq表达谱高度相关。