shikonin and methyl-jasmonate

Alkannin/shikonin and their derivatives are specialised metabolites of high pharmaceutical and ecological importance exclusively produced in the periderm of members of the plant family Boraginaceae. Previous studies have shown that their biosynthesis is induced in response to methyl jasmonate but not salicylic acid, two phytohormones that play important roles in plant defence. However, mechanistic understanding of induction and non-induction remains largely unknown. In the present study, we generated the first comprehensive transcriptomic dataset and metabolite profiles of Lithospermum officinale plants treated with methyl jasmonate and salicylic acid to shed light on the underlying mechanisms. Our results highlight the diverse biological processes activated by both phytohormones and reveal the important regulatory role of the mevalonate pathway in alkannin/shikonin biosynthesis in L. officinale. Furthermore, by modelling a coexpression network, we uncovered structural and novel regulatory candidate genes connected to alkannin/shikonin biosynthesis. Besides providing new mechanistic insights into alkannin/shikonin biosynthesis, the generated methyl jasmonate and salicylic acid elicited expression profiles together with the coexpression networks serve as important functional genomic resources for the scientific community aiming at deepening the understanding of alkannin/shikonin biosynthesis.

Topics: Acetates; Cyclopentanes; Lithospermum; Mevalonic Acid; Naphthoquinones; Oxylipins; Pharmaceutical Preparations; Plant Growth Regulators; Salicylic Acid

The shikonin derivatives, accumulated in the roots of Arnebia euchroma (Boraginaceae), showed antibacterial, anti-inflammatory, and anti-tumor activities. To explore their possible biosynthesis regulation mechanism, this paper investigated the effects of exogenous methyl jasmonate (MJ) on the biosynthesis of shikonin derivatives in callus cultures of A. euchroma. The main results include: Under MJ treatment, the growth of A. euchroma callus cultures was not inhibited, but the expression level of both the genes involved in the biosynthesis of shikonin derivatives and their precursors and the genes responsible for intracellular localization of shikonin derivatives increased significantly in the Red Strain (shikonin derivatives high-producing strain). The quantitative analysis showed that six out of the seven naphthoquinone compounds under investigation increased their contents in the MJ-treated Red Strain, and in particular, the bioactive component acetylshikonin nearly doubled its content in the MJ-treated Red Strain. In addition, it was also observed that the metabolic profiling of naphthoquinone compounds changed significantly after MJ treatment, and the MJ-treated and MJ-untreated strains clearly formed distinct clusters in the score plot of PLS-DA. Our results provide some new insights into the regulation mechanism of the biosynthesis of shikonin derivatives and a possible way to increase the production of naphthoquinone compounds in A. euchroma callus cultures in the future.

Topics: Acetates; Boraginaceae; Cell Culture Techniques; Cyclopentanes; Naphthoquinones; Oxylipins; Plant Proteins; Plant Roots