Su Lingye, Li Shufang, Qiu Hanhan, Wang Hongfeng, Wang Congcong, He Chunmei, Xu Mingfeng, Zhang Zongshen
Guangdong Provincial Key Laboratory of Silviculture Protection and Utilization, Guangdong Academy of Forestry, Guangzhou, China.
School of Biology Engineering, Dalian Polytechnic University, Dalian, China.
Front Genet. 2021 Mar 29;12:657060. doi: 10.3389/fgene.2021.657060. eCollection 2021.
Triterpenoid saponins constitute a diverse class of bioactive compounds in medicinal plants. Salicylic acid (SA) is an efficient elicitor for secondary metabolite production, but a transcriptome-wide regulatory network of SA-promoted triterpenoid saponin biosynthesis remains little understood. In the current study, we described the establishment of the hairy root culture system for , a triterpenoid saponin-producing medicinal herb in China, using genetic transformation by . Compared to controls, we found that total saponin content was dramatically increased (up to 2.49-fold) by the addition of 5 mg/L SA in hairy roots for 1 day. A combination of single-molecule real-time (SMRT) and next-generation sequencing (Illumina RNA-seq) was generated to analyze the full-length transcriptome data for , as well as the transcript profiles in treated (8 and 24 h) and non-treated (0 h) groups with 5 mg/L SA in hairy roots. A total of 430,117 circular consensus sequence (CCS) reads, 16,375 unigenes and 4,678 long non-coding RNAs (lncRNAs) were obtained. The average length of unigenes (2,776 bp) was much higher in full-length transcriptome than that derived from single RNA-seq (1,457 bp). The differentially expressed genes (DEGs) were mainly enriched in the metabolic process. SA up-regulated the unigenes encoding SA-binding proteins and antioxidant enzymes in comparison with controls. Additionally, we identified 89 full-length transcripts encoding enzymes putatively involved in saponin biosynthesis. The candidate transcription factors (WRKY, NAC) and structural genes (, , , ) might be the key regulators in SA-elicited saponin accumulation. Their expression was further validated by quantitative real-time PCR (qRT-PCR). These findings preliminarily elucidate the regulatory mechanisms of SA on triterpenoid saponin biosynthesis in the transcriptomic level, laying a foundation for SA-elicited saponin augmentation in .
三萜皂苷是药用植物中一类多样的生物活性化合物。水杨酸（SA）是次生代谢产物产生的有效诱导剂，但SA促进三萜皂苷生物合成的全转录组调控网络仍知之甚少。在本研究中，我们描述了利用发根农杆菌介导的遗传转化建立中国产三萜皂苷药用植物[具体植物名称未给出]的毛状根培养系统。与对照相比，我们发现，在毛状根中添加5 mg/L SA处理1天，总皂苷含量显著增加（高达2.49倍）。采用单分子实时（SMRT）测序和二代测序（Illumina RNA-seq）相结合的方法，分析了[具体植物名称未给出]的全长转录组数据，以及毛状根中5 mg/L SA处理组（8小时和24小时）和未处理组（0小时）的转录谱。共获得430,117条环状一致序列（CCS） reads、16,375个单基因和4,678个长链非编码RNA（lncRNA）。全长转录组中，单基因的平均长度（2,776 bp）远高于单RNA-seq获得的单基因平均长度（1,457 bp）。差异表达基因（DEG）主要富集在代谢过程中。与对照相比，SA上调了编码SA结合蛋白和抗氧化酶的单基因。此外，我们鉴定出89个全长转录本，其编码的酶可能参与皂苷生物合成。候选转录因子（WRKY、NAC）和结构基因（[具体基因名称未给出]）可能是SA诱导皂苷积累的关键调控因子。通过实时定量PCR（qRT-PCR）进一步验证了它们的表达。这些发现初步阐明了转录组水平上SA对三萜皂苷生物合成的调控机制，为[具体植物名称未给出]中SA诱导皂苷增加奠定了基础。
