The Key Laboratory of Plant Ecology, Northeast Forestry University, Harbin, 150040, China.
Guizhou Academy of Tobacco Research, Guiyang, 550081, China.
BMC Genomics. 2018 Jul 2;19(1):508. doi: 10.1186/s12864-018-4879-3.
The medicinal plant, Catharanthus roseus (C. roseus), accumulates a wide range of terpenoid indole alkaloids (TIAs). Ethylene (ET) and methyl-jasmonate (MeJA) were previously reported as effective elicitors for the production of various valuable secondary metabolites of C. roseus, while a few ET or MeJA induced transcriptomic research is yet reported on this species. In this study, the de-novo transcriptome assembly of C. roseus is performed by using the next-generation sequencing technology.
The result shows that phenolic biosynthesis genes respond specifically to ET in leaves, monoterpenoid biosynthesis genes respond specifically to MeJA in roots. By screening the database, 23 ATP-binding cassette (ABC) transporter partial sequences are identified in C. roseus. On this basis, more than 80 key genes that encode key enzymes (namely TIA pathway, transcriptional factor (TF) and candidate ABC transporter) of alkaloid synthesis in TIA biosynthetic pathways are chosen to explore the integrative responses to ET and MeJA at the transcriptional level. Our data indicated that TIA accumulation is strictly regulated by the TF ethylene responsive factor (ERF) and bHLH iridoid synthesis 1 (BIS1). The heatmap, combined with principal component analysis (PCA) of C. roseus, shows that ERF co-expression with ABC2 and ABC8 specific expression in roots affect the root-specific accumulation of vinblastine in C. roseus. On the contrast, BIS1 activities follow a similar pattern of ABC3 and CrTPT2 specific expression in leaves, which affects the leaf-specific accumulation of vindoline in C. roseus.
Results presented above illustrate that ethylene has a stronger effect than MeJA on TIA induction at both transcriptional and metabolite level. Furthermore, meta-analysis reveals that ERF and BIS1 form a positive feedback loop connecting two ABC transporters respectively and are actively involved in TIAs responding to ET and MeJA in C. roseus.
药用植物长春花（C. roseus）积累了广泛的萜类吲哚生物碱（TIAs）。乙烯（ET）和茉莉酸甲酯（MeJA）先前被报道为有效诱导物，可产生长春花的各种有价值的次生代谢产物，而关于该物种的少数 ET 或 MeJA 诱导的转录组研究尚未报道。在这项研究中，使用下一代测序技术对长春花的 de-novo 转录组进行组装。
结果表明，酚类生物合成基因对叶片中的 ET 有特异性响应，单萜生物合成基因对根中的 MeJA 有特异性响应。通过筛选数据库，在长春花中鉴定出 23 个 ATP 结合盒（ABC）转运体部分序列。在此基础上，选择了 80 多个关键基因，这些基因编码 TIA 生物合成途径中生物碱合成的关键酶（即 TIA 途径、转录因子（TF）和候选 ABC 转运体），以在转录水平上探索对 ET 和 MeJA 的综合响应。我们的数据表明，TIA 的积累受到 TF 乙烯响应因子（ERF）和 bHLH 吲哚苷合成 1（BIS1）的严格调控。长春花的热图，结合主成分分析（PCA），表明 ERF 与 ABC2 和 ABC8 在根中的特异性表达共同影响长春花中长春碱的根特异性积累。相比之下，BIS1 活性遵循叶片中 ABC3 和 CrTPT2 特异性表达的类似模式，这影响了长春花中 vindoline 的叶特异性积累。
上述结果表明，乙烯在转录和代谢物水平上对 TIA 诱导的作用强于 MeJA。此外，荟萃分析表明，ERF 和 BIS1 分别形成一个正反馈回路，连接两个 ABC 转运体，并积极参与 ET 和 MeJA 诱导的 TIAs 在长春花中的反应。
