Enhanced tolerance of industrial hemp (Cannabis sativa L.) plants on abandoned mine land soil leads to overexpression of cannabinoids

Abstract

Industrial activities have a detrimental impact on the environment and health when high concentrations of pollutants are released. Phytoremediation is a natural method of utilizing plants to remove contaminants from the soil. The goal of this study was to investigate the ability of Cannabis sativa L. to sustainably grow and remediate abandoned coal mine land soils in Pennsylvania. In this study, six different varieties of industrial hemp (Fedora 17, Felina 32, Ferimon, Futura 75, Santhica 27, and USO 31) were grown on two different contaminated soil types and two commercial soils (Miracle-Gro Potting Mix and PRO-MIX HP Mycorrhizae High Porosity Grower Mix). Plants growing in all soil types were exposed to two environmental conditions (outside and in the greenhouse). Seed germination response and plant height indicated no significant differences among all hemp varieties grown in different soils, however on an average, the height of the plants grown in the greenhouse exceeded that of the plants grown outdoors. In addition, heavy metal analysis of Arsenic, Lead, Nickel, Mercury, and Cadmium was performed. The concentration of Nickel was 2.54 times greater in the leaves of hemp grown in mine land soil outdoors when compared to greenhouse conditions. No differences were found between expression of heavy metal transporter genes. Secondary metabolite analysis of floral buds from hemp grown in mine land soil displayed a significant increase in the total Cannabidiol content (2.16%, 2.58%) when compared to Miracle-Gro control soil (1.08%, 1.6%) for outdoors and in the greenhouse, respectively. Molecular analysis using qRT-PCR indicated an 18-fold increase in the expression of the cannabidiolic acid synthase gene in plants grown on mine land soil. The data indicates a high tolerance to heavy metals as indicated from the physiological and metabolites analysis.

Potential of hemp (Cannabis sativa L.) for paired phytoremediation and bioenergy production

“…Since phytoremediation is influenced by cultivar selection and plant genetics (Adamovičs et al, 2014;Mihoc et al, 2012;Petrová et al, 2012;Shi et al, 2012), the legal limitation of hemp based on low THC content dramatically reduces the number of C. sativa varieties that can be investigated for combined phytoremediation and bioenergy production. Furthermore, research has indicated that cannabinoids are overexpressed as a result of heavy metal accumulation (Husain et al, 2019), which has the potential to exacerbate legality issues when hemp is used for phytoremediation. This area might be expanded with special policy exceptions, such as those granted to hemp breeders for variety development, to F I G U R E 1 Flow chart for production of bioenergy from hemp, adapted from process diagrams described in Kreuger, Prade, et al (2011) Maximal 137 Cs soil contamination levels calculated using the lower value for the decontamination factor listed.…”

Genome-Wide Identification of MYB Gene Family Reveals Their Potential Functions in Cadmium Stress Response and the Regulation of Cannabinoid Biosynthesis in Hemp (Cannabis sativa L.)

“…Systematic identification of the whole hemp genome and related research into Cd stress is necessary. In recent years, studies have found that exogenous heavy metal stress can increase CBD, a representative cannabinoid, content in hemp [19]. One of the objectives of this study was to determine whether Cd stress leads to changes in the content of cannabinoids by affecting the expression of MYB genes.…”

Metabolic Engineering Strategies of Industrial Hemp (Cannabis sativa L.): A Brief Review of the Advances and Challenges

“…These transcription factors are targets to activate cannabinoid synthesis. Notably, cannabinoid synthesis is expedited by UV light application or heavy metal ( Zhang and Björn, 2009 ; Husain et al, 2019 ). The elucidation of signal transduction triggered by these elicitors may lead to the discovery of positive and negative regulators of signal transduction, which will be the target genes for hemp metabolic engineering.…”