Citation: Mihálik, D.; Hanˇ cinský, R.; Kaˇ nuková, Š.; Mrkvová, M.; Kraic, J. Elicitation of Hyoscyamine Production in Datura stramonium L. Plants Using Tobamoviruses. Plants 2022, 11, 3319. https://doi.org/ 10.3390/plants11233319 Academic Editors: Laura Grat , iela Vicas , and Mariana Eugenia Mures , an Received: 6 November 2022 Accepted: 29 November 2022 Published: 1 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Brief Report Elicitation of Hyoscyamine Production in Datura stramonium L. Plants Using Tobamoviruses Daniel Mihálik 1,2 , Richard Hanˇ cinský 1 , Šarlota Ka ˇ nuková 2 , Michaela Mrkvová 1,2 and Ján Kraic 1,2, * 1 National Agricultural and Food Centre, Research Institute of Plant Production, Bratislavská cesta 122, 92168 Piešt’any, Slovakia 2 Faculty of Natural Sciences, University of Ss. Cyril and Methodius, Nám. J. Herdu 2, 91701 Trnava, Slovakia * Correspondence: jan.kraic@ucm.sk Abstract: Datura stramonium L. produces tropane alkaloids, and the hyoscyamine is dominant among them. Hyoscyamine is produced by hairy root cultures in vitro derived from native plants or plants with the genetically modified biosynthetic pathway for hyoscyamine. A common procedure is extraction from cultivated plants. Elicitors for increased production can be used in both cases. Live viruses are not well known for use as elicitors, therefore, D. stramonium plants grown in soil were artificially infected with the tobamoviruses Pepper mild mottle virus (PMMoV), Tomato mosaic virus (ToMV), and Tobacco mosaic virus (TMV). Differences in the content of hyoscyamine were between capsules and roots of infected and non-infected plants. Elicitation increased content of hyoscyamine in capsules 1.23–2.34 times, compared to the control. The most effective viruses were PMMoV and ToMV (isolate PV143), which increased content to above 19 mg/g of fresh weight of a capsule. The effect of each virus elicitor was expressed also in hyoscyamine content in roots. Elicited plants contained 5.41–16.54 times more hyoscyamine in roots compared to non-elicited plants. The most effective elicitor was ToMV SL-1, which raised production above 20 mg/g fresh weight of roots. It has been shown that tobamoviruses can be used as biotic elicitors. Keywords: thorn apple; tropane alkaloid; in vivo; virus infection; TMV; ToMV; PMMoV 1. Introduction Datura stramonium L. is known under different names (thorn apple, jimsonweed, devil’s snare, devil’s trumpet). It is an annual herb from the Solanaceae family, native to the southwest of the USA, Mexico, Central America, and the Greater Antilles. Currently, it is spread worldwide and belongs to the cosmopolitan weed species [1]. The whole plant, including the seeds, is poisonous. The plant can be dangerous, especially because of possible contamination of livestock feed. D. stramonium L. contains a variety of alkaloids, saponins, tannins, steroids, flavonoids, phenols, and glycosides [2]. Twenty-five tropane alkaloids were identified in its roots, leaves, and seeds using gas chromatography-mass spectrometry (GC-MS) [3]. Later, the number of identified tropane alkaloids increased to more than sixty [4]. The most interesting among them are hyoscyamine, atropine, and scopolamine. These compounds potently regulate the human central nervous system. The hyoscyamine has remarkable effects in the treatment of Parkinson’s disease, bradyarrhyth- mias, genitourinary symptoms, and others [5]. Hyoscyamine is the major tropane alkaloid in D. stramonium L. [3,6], is a precursor for the synthesis of scopolamine, and an enantiomer of atropine that is formed by racemization during the extractive procedure. D. stramonium is an interesting plant species due to medicinal applications of tropane alkaloids. The demand for tropane alkaloids can be fulfilled by chemical synthesis or by biotechnological production. They can be produced biotechnologically using in vitro cell suspension cultures derived from D. stramonium L. [7] or root cultures established from native or transgenic hairy roots [8]. An alternative is the heterologous production of tropane Plants 2022, 11, 3319. https://doi.org/10.3390/plants11233319 https://www.mdpi.com/journal/plants