De novo transcriptome analysis reveals the effects of abiotic and biotic elicitation on naphthoquinone and flavonoid production in Lawsonia inermis L

Lawsonia inermis L. is a medicinally and commercially important plant, contributing to 9% of India’s medicinal exports. The growing demand for its principal phytochemical (lawsone) is difficult to be met through traditional farming. Although elicitation can help in augmentation of phytochemicals, the absence of a reference genome limits our understanding of the underlying molecular mechanisms leading to enhanced secondary metabolite production. This study amalgamates elicitation and transcriptomics in understanding the augmentation of lawsone, rutin, and kaempferol. Salicylic acid(50 µM) was the best abiotic elicitor, followed by yeast extract (biotic elicitor), enhancing the secondary metabolite content. In vitro plants, treated with salicylic acid (50 µM) showed 1–2 times more accumulation of lawsone, rutin, kaempferol, 5–10 time more secondary metabolite accumulation, as compared to control in vitro plants. Transcriptome assembly generated 23,648 unigenes. Further analysis revealed genes involved in phenylpropanoid, flavonoid, terpenoid and lawsone biosynthetic pathways to be upregulated in salicylic acid treatment. RT-qPCR showed enhanced expression of PAL, CHS, HST, COQ4, FQRL, MenE, MenB and MenD genes, responsible for the enhanced secondary metabolite in the plant. Collectively, these findings provide an elicitor-induced production of secondary metabolites, which can pave the way for future manipulation and sustainable production of these phytochemicals for industrial need.