Intraspecific divergence in essential oil content, composition and genes expression patterns of monoterpene synthesis in Origanum vulgare subsp. vulgare and subsp. gracile under salinity stress

• Published in: BMC plant biology Vol. 23; no. 1; p. 380
• Main Authors: Azimzadeh, Zahra, Hassani, Abbas, Mandoulakani, Babak Abdollahi, Sepehr, Ebrahim, Morshedloo, Mohammad Reza
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 07-08-2023; BioMed Central; BMC
• Subjects: 1-deoxy-D-xylulose-5-phosphate reductoisomerase; Agricultural production; Antioxidants; Antiviral agents; Biosynthesis; Botanical research; Carvacrol; Chemical composition; Chemical properties; Composition; Cytochrome P450; Cytochromes P450; D-Xylulose 5-phosphate; Divergent evolution; Environmental stress; Erythritol; Essences and essential oils; Essential oils; Gene expression; Genes; Genetic aspects; Genetic research; Herbal medicine; Hydrocarbons; Inflammation; Medical importance; Medicinal plants; Medicine, Botanic; Medicine, Herbal; Metabolites; Monosaccharides; Monoterpenes; Muscle relaxants; Neuroprotection; Oils & fats; Oregano; Origanum vulgare; Origanum vulgare L; Parasympathetic nervous system; Phenolic compounds; Phenols; Phosphates; Physiological aspects; Plant growth; Plant metabolites; Reductoisomerase; Salinity; Salinity effects; Salinity stress; Salt stress (Botany); Secondary metabolites; Sodium chloride; Sugars; Terpinene; Thymol; Xylulose; γ-Terpinene synthase; Iran; Salinity stress; 1-deoxy-D-xylulose-5-phosphate reductoisomerase; Carvacrol; Origanum vulgare L; γ-Terpinene synthase; Gene expression
• ISSN: 1471-2229; 1471-2229
• DOI: 10.1186/s12870-023-04387-5

Oregano (Origanum vulgare L.), one of the important medicinal plants in the world, has valuable pharmacological compounds with antimicrobial, antiviral, antioxidant, anti-inflammatory, antispasmodic, antiurolithic, antiproliferative and neuroprotective activities. Phenolic monoterpenes such as thymol and carvacrol with many medical importance are found in Oregano essential oil. The biosynthesis of these compounds is carried out through the methyl erythritol-4 phosphate (MEP) pathway. Environmental stresses such as salinity might improve the secondary metabolites in medicinal plants. The influence of salinity stress (0 (control), 25, 50 and 100 mM NaCl) on the essential oil content, composition and expression of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), γ-terpinene synthase (Ovtps2) and cytochrome P450 monooxygenases (CYP71D180) genes involved in thymol and carvacrol biosynthesis, was investigated in two oregano subspecies (vulgare and gracile).
Essential oil content was increased at low NaCl concentration (25 mM) compared with non-stress conditions, whereas it was decreased as salinity stress intensified (50 and 100 mM). Essential oil content was significantly higher in subsp. gracile than subsp. vulgare. The highest (0.20 mL pot
) and lowest (0.06 mL pot
) amount of essential oil yield was obtained in subsp. gracile at 25 and 100 mM NaCl, respectively. The content of carvacrol, as the main component of essential oil, decreased with increasing salinity level in subsp. gracile, but increased in subsp. vulgare. The highest expression of DXR, Ovtps2 and CYP71D180 genes was observed at 50 mM NaCl in subsp. vulgare. While, in subsp. gracile, the expression of the mentioned genes decreased with increasing salinity levels. A positive correlation was obtained between the expression of DXR, Ovtps2 and CYP71D180 genes with carvacrol content in both subspecies. On the other hand, a negative correlation was found between the expression of CYP71D180 and carvacrol content in subsp. gracile.
The findings of this study demonstrated that both oregano subspecies can tolerate NaCl salinity up to 50 mM without significant reduction in essential oil yield. Also, moderate salinity stress (50 mM NaCl) in subsp. vulgare might increase the carvacrol content partly via increment the expression levels of DXR, Ovtps2 and CYP71D180 genes.