De novo leaf and root transcriptome analysis identified novel genes involved in Steroidal sapogenin biosynthesis in Asparagus racemosus

Abstract

BackgroundSaponins are mainly amphipathic glycosides that posses many biological activities and confer potential health benefits to humans. Inspite of its medicinal attributes most of the triterpenes and enzymes involved in the saponin biosynthesis remains uncharacterized at the molecular level. Since the major steroidal components are present in the roots of A. racemosus our study is focussed on the comparative denovo transcriptome analysis of root versus leaf tissue and identifying some root specific transcripts involved in saponin biosynthesis using high-throughput next generation transcriptome sequencing.ResultsAfter sequencing, de novo assembly and quantitative assessment, 126861 unigenes were finally generated with an average length of 1200 bp. Then functional annotation and GO enrichment analysis was performed by aligning all-unigenes with public protein databases including NR, SwissProt, and KEGG. Differentially expressed genes in root were initially identified using the RPKM method using digital subtraction between root and leaf. Twenty seven putative secondary metabolite related transcripts were experimentally validated for their expression in root or leaf tissue using q-RT PCR analysis. Most of the above selected transcripts showed preferential expression in root as compared to leaf supporting the digitally subtracted result obtained. The methyl jasmonate application induces the secondary metabolite related gene transcripts leading to their increased accumulation in plants. Therefore, the identified transcripts related to saponin biosynthesis were further analyzed for their induced expression after 3, 5 and 12 hours of exogenous application of Methyl Jasmonate in tissue specific manner.ConclusionsIn this study, we have identified a large set of cDNA unigenes from A. racemosus leaf and root tissue. This is the first transcriptome sequencing of this non-model species using Illumina, a next generation sequencing technology. The present study has also identified number of root specific transcripts showing homology with saponin biosynthetic pathway. An integrated pathway of identified saponin biosynthesis transcripts their tissue specific expression and induced accumulation after methyl jasmonate treatment was discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-746) contains supplementary material, which is available to authorized users.

Recent advances in steroidal saponins biosynthesis and in vitro production

“…Leaf versus root transcriptome of Asparagus racemosus using Illumina Wang et al (2016aWang et al ( , 2016b 1 3 sequencing approach revealed that majority of transcripts related to steroidal saponin biosynthesis including P450 and UDP-glucosyltransferase was found to be upregulated in root tissue as compared to leaf. This will lead to the hypothesis that steroidal saponin accumulated in the roots of Asparagus racemosus, which is mainly responsible for its pharmacological properties (Upadhyay et al 2014). …”

Comparative transcriptome analysis of root, stem, and leaf tissues of Entada phaseoloides reveals potential genes involved in triterpenoid saponin biosynthesis

“…It was found that the content of triterpenes accumulated in the leaves of P. ginseng are higher in the early growth stage, while the content of triterpenes in the roots of old plants are higher [27]. Comparative transcriptome analysis including root and leaf tissues to excavate transcripts related to saponin biosynthesis is already reported for many plants, such as Hedera helix [28], Panax notoginseng [29] and Asparagus racemosus [26]. The maximum triterpenoid saponin content was identi ed in stem.…”

“…Recently, transcriptome assay with next-generation sequencing has been extensively used to explore the novel genes underlying active-ingredient biosynthesis pathways in medicinal plants. Some include the excavation of genes encoding enzymes that catalyze distinct steps related to the biosynthetic pathway of ginsenosides in Panax ginseng [13], triterpenoid saponin biosynthesis in Bacopa monnieri [14], artemisinin in Artemisia annua [15,16], avonoid biosynthesis in sa ower [17], glycyrrhizin in Glycyrrhiza uralensis [18], rubber in Parthenium argentatum [19], cardiac glycoside in Calotropis procera [20], terpenoid in Cinnamomum camphora [21], cannabinoids in Cannabis sativa [22], withanolide in Withania somnifera [23], picrosides in Picrorhiza kurrooa [24], paclitaxel in Taxus chinensis [25] and steroidal saponins in Asparagus racemosus [26].…”

Transcriptome analysis of Leucaena leucocephala and identification of highly expressed genes in roots and shoots

“…For example, in the root of Valeriana fauriei (valerian), which is used for medicinal purposes, the terpenoid biosynthesis genes were highly upregulated [43]. Another plant Asparagus racemosus, whose tuberous roots are used in traditional Indian medicine, showed upregulation of terpenoid biosynthesis genes in roots compared to leaves [44]. On the other hand, in Cymbopogon winterianus (citronella), whose leaves are known to have antimicrobial properties, shows higher expression of terpenoid biosynthesis genes in leaves compared to roots [45].…”