Targeted expression of Vitreoscilla hemoglobin improves the production of tropane alkaloids in Hyoscyamus niger hairy roots

Abstract

Under hypoxic conditions, the expression of Vitreoscilla hemoglobin (VHb) in plants is proposed to increase the productivity of certain oxygen-requiring metabolic pathways by promoting the delivery of oxygen. Tropane alkaloids (TAs) are a class of important plant secondary metabolites with significant medicinal value; the final step in their biosynthesis requires oxygen. Whether heterologous expression of VHb, especially in different subcellular compartments, can accelerate the accumulation of TAs is not known. Herein, the effect of heterologous expression of VHb in different subcellular locations on the TA profile of H. niger hairy roots was investigated. The targeted expression of VHb in the plastids (using pVHb-RecA construct), led to the accumulation of 197.68 μg/g hyoscyamine in the transgenic H. niger hairy roots, which was 1.25-fold of the content present in the lines in which VHb expression was not targeted, and 3.66-fold of that present in the wild type (WT) lines. The content of scopolamine was increased by 2.20- and 4.70-fold in the pVHb-RecA transgenic lines compared to that in the VHb transgenic and WT lines. Our results demonstrate that VHb could stimulate the accumulation of TAs in the transgenic H. niger hairy roots. Quantitative RT-PCR analysis revealed that the expression of key genes involved in TA biosynthesis increased significantly in the VHb transgenic lines. We present the first description of a highly efficient strategy to increase TA content in H. niger. Moreover, our results also shed light on how the production of desired metabolites can be efficiently enhanced by using more accurate and appropriate genetic engineering strategies.

Production of Vitamin E in Erwinia herbicola Bearing the Vitreoscilla Hemoglobin Gene (vgb+)

“…It was strongly demonstrated that the concentration sugar was greatly enhanced by over expression of the VHb and on the other hand, the cell growth was almost the similar [47]. Some studies showed that expression of vgb gene was effective on the production several metabolites [10,38,[48][49][50]. In addition, vgbstrain showed more or less similar results with vgb + in both intra-and extracellular vitamin production.…”

Effects of Water Availability in the Soil on Tropane Alkaloid Production in Cultivated Datura stramonium

“…This chemical transformation is conceptualized as two concerted reactions: (i) the hydroxylation of atropine followed by (ii) the cyclization of anisodamine to form an epoxide between the carbon atoms C6 and C7. The two reactions are assumed to be catalyzed in vivo by a single enzyme: hyoscyamine-6β-hydroxylase (H6H, EC 1.14.11.11) [28]. H6H has been cloned from different Solanaceae [29].…”

Transgenesis as a Tool for the Efficient Production of Selected Secondary Metabolites from Plant in Vitro Cultures

“…So far, many attempts have been made to induce hairy roots with specific traits, most of which are based on genetic engineering techniques that allow plant material with increased utility values to be obtained. A good example of this approach is the heterologous expression of Vitreoscilla hemoglobin in plastids using the pVHb-RecA construct, leading to increased production of hyoscyamine and scopolamine in Hyoscyamus niger L. in vitro transgenic plant cultures [62]. Another is the possibility of affecting the increase in the content of glycyrrhizic acid by overexpression of the β-amyrin synthase gene in hairy roots of Glycyrrhiza uralensis Fisch.…”