Transcriptome analysis explores genes related to shikonin biosynthesis in Lithospermeae plants and provides insights into Boraginales\u2019 evolutionary history

Feng-Yao Wu,Yu-Min Guo,Jin-Liang Qi,Zhuo-Wu Bian,Gui-Hua Lu,Jiang-Yan Fu,Yan-Jun Pang,Cheng-Yi Tang,Yong-Hua Yang

doi:10.1038/s41598-017-04750-1

Abstract

Shikonin and its derivatives extracted from Lithospermeae plants’ red roots have current applications in food and pharmaceutical industries. Previous studies have cloned some genes related to shikonin biosynthesis. However, most genes related to shikonin biosynthesis remain unclear, because the lack of the genome/transcriptome of the Lithospermeae plants. Therefore, in order to provide a new understanding of shikonin biosynthesis, we obtained transcriptome data and unigenes expression profiles in three shikonin-producing Lithospermeae plants, i.e., Lithospermum erythrorhizon, Arnebia euchroma and Echium plantagineum. As a result, two unigenes (i.e., G10H and 12OPR) that are involved in “shikonin downstream biosynthesis” and “methyl jasmonate biosynthesis” were deemed to relate to shikonin biosynthesis in this study. Furthermore, we conducted a Lamiids phylogenetic model and identified orthologous unigenes under positive selection in above three Lithospermeae plants. The results indicated Boraginales was more relative to Solanales/Gentianales than to Lamiales.

Highlights

Shikonin and its derivatives, red naphthoquinones, are widely found in the epidermis of the roots of the Lithospermeae plants, such as genera Lithospermum, Arnebia and Echium[1,2,3]
In the past 30 years, several genes that encoding enzymes directly involved in the shikonin biosynthesis, such as hydroxymethylglutaryl-CoA synthase gene (HMGS), hydroxymethylglutaryl-CoA reductase gene (HMGR), phenylalanine ammonia lyase (PAL), cinnamate 4-monooxygenase (C4H) and p-hydroxybenzoate geranyltransferase gene (PGT), have been cloned and characterized in L. erythrorhizon or A. euchroma[8,9,10,11,12]
Shikonin biosynthesis should exist only in the RR lines rather than GL lines in the three Lithospermeae plants assessed in this present study (Fig. 1 and Supplementary Table S1)

Summary

Introduction

Shikonin and its derivatives, red naphthoquinones, are widely found in the epidermis of the roots of the Lithospermeae plants, such as genera Lithospermum, Arnebia and Echium[1,2,3]. In order to provide a new understanding of shikonin biosynthesis, we performed transcriptome analysis for three Lithospermeae plants, i.e., L. erythrorhizon, A. euchroma and E. plantagineum. The results indicated that two unigenes (i.e., G10H and 12OPR) were related to shikonin biosynthesis in this present study.

Results

Conclusion