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Open Access Research article

The root transcriptome for North American ginseng assembled and profiled across seasonal development

Di Wu12, Ryan S Austin2, Sijun Zhou12 and Dan Brown123*

  • * Corresponding author: Dan Brown dbrown@sbrc.ca

  • † Equal contributors

Author Affiliations

1 Western University, 1151 Richmond St, London, ON, Canada

2 Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON, Canada

3 Canadian Centre for Agri-food Research in Health and Medicine (CCARM), St. Boniface Hospital, 351 Taché Avenue, Winnipeg, MN, Canada

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BMC Genomics 2013, 14:564  doi:10.1186/1471-2164-14-564

Published: 19 August 2013

Abstract

Background

Ginseng including North American ginseng (Panax quinquefolius L.) is one of the most widely used medicinal plants. Its success is thought to be due to a diverse collection of ginsenosides that serve as its major bioactive compounds. However, few genomic resources exist and the details concerning its various biosynthetic pathways remain poorly understood. As the root is the primary tissue harvested commercially for ginsenosides, next generation sequencing was applied to the characterization and assembly of the root transcriptome throughout seasonal development. Transcripts showing homology to ginsenoside biosynthesis enzymes were profiled in greater detail.

Results

RNA extracts from root samples from seven development stages of North American ginseng were subjected to 454 sequencing, filtered for quality and used in the de novo assembly of a collective root reference transcriptome consisting of 41,623 transcripts. Annotation efforts using a number of public databases resulted in detailed annotation information for 34,801 (84%) transcripts. In addition, 3,955 genes were assigned to metabolic pathways using the Kyoto Encyclopedia of Genes and Genomes. Among our results, we found all of the known enzymes involved in the ginsenoside backbone biosynthesis and used co-expression analysis to identify a number of candidate sequences involved in the latter stages ginsenoside biosynthesis pathway. Transcript profiles suggest ginsenoside biosynthesis occurs at distinct stages of development.

Conclusions

The assembly generated provides a comprehensive annotated reference for future transcriptomic study of North American ginseng. A collection of putative ginsenoside biosynthesis genes were identified and candidate genes predicted from the lesser understood downstream stages of biosynthesis. Transcript expression profiles across seasonal development suggest a primary dammarane-type ginsenoside biosynthesis occurs just prior to plant senescence, with secondary ginsenoside production occurring throughout development. Data from the study provide a valuable resource for conducting future ginsenoside biosynthesis research in this important medicinal plant.

Keywords:
North American ginseng; Transcriptome; Next generation sequencing; Ginsenoside