Sahar Tadili, Ali Asghari *1, Noraddin Hosseinpour Azad, Ehsan Shokri, Seyyed Hamidreza Hashemi Patroudi
Abstract: (6 Views)
Background: Capparis ovata, commonly known as "caper bush," belongs to the Capparidaceae family. This perennial, drought-tolerant plant is widely distributed across arid and semi-arid regions of the Middle East and the Mediterranean. It is also known by other names such as "kavar","lagaji" or "mountain watermelon". Due to its high adaptability to harsh environmental conditions and its content of bioactive compounds particularly glucosinolates, this species holds significant ecological and medicinal value. These secondary metabolites, through enzymes such as myrosinase and thioglucoside glucohydrolase (TTG), play crucial roles in the plant's defense mechanisms. Despite increasing interest in C. ovata as a drought-resistant medicinal plant, little is known about its molecular responses to environmental stresses such as ionizing radiation. Radon is a naturally occurring radioactive gas and one of the main sources of environmental ionizing radiation. While its effects on human health are well documented, its impact on plant molecular biology remains largely unknown. Myrosinase and TTG are two key enzymes in C. ovata, involved in plant defense against herbivores by hydrolyzing glucosinolates. The aim of this study was to investigate the effect of environmental radon exposure on the expression of myrosinase and TTG genes in C. ovata.
Methods: Plant samples were collected from the mountain of Kojanagh village, located 18 km northwest of Meshginshahr (geographical coordinates: 38°29'17.7" N, 47°30'15.1" E). All geographic calculations were performed using a Garmin Oregon 650 GPS device. To obtain comprehensive information on the region’s radiation pollution, a point-by-point radon radiation map was prepared at 10 locations using a Victoreen 451 radiation meter (Fluke Biomedical Company, USA) over two consecutive years. These measurements included points at similar elevations on two adjacent mountains one with radioactive exposure (A) and one without exposure (B). Total RNA was extracted from leaf tissue, and cDNA for myrosinase and TTG genes was synthesized for expression analysis (qRT-PCR). Gene expression levels were normalized to actin as a reference gene. Relative gene expression was calculated using the 2−ΔCt method, with actin as the internal control. Statistical analysis was performed with GraphPad Prism 10 (GraphPad Software, USA). Differences in gene expression between radon-exposed and control samples were evaluated using independent t-tests, with significance set at P<0.05.
Results: Analysis of myrosinase gene expression in C. ovata under varying radon gas levels showed that the highest increase occurred at elevations of 910–920 meters (site A) with an average radiation intensity of 0.8 mSv, where gene expression exceeded seven times that of the non-radioactive control area. At elevations of 930–940 meters (site A) with an average intensity of 1.8 mSv, a roughly fourfold increase was observed compared to the control. In other elevations, gene expression was lower. These findings suggest a nonlinear, elevation-dependent response in myrosinase gene expression, with optimal stimulation at mid-elevations (910–920 meters). The TTG gene expression pattern showed similar changes across elevation ranges, with the highest expression also at 910–920 meters (about fourfold higher than the control). In this range, the standard error was relatively high, indicating variability among samples. A significant increase was also observed at 880–900 meters (about 2.5 times higher than control). At lower (830–860 meters) and higher (950–1000 meters) elevations, expression levels were approximately 1.5 and 1.8 times higher, respectively. The lowest gene expression, like myrosinase, was observed at 880–900 meters. Both Myro and TTG genes exhibited similar expression patterns under different radon exposures, with the highest increase at mid-elevations (910–920 meters, 0.8 mSv average radiation).involved. This study highlights Myro as a potential molecular marker for radon stress in C. ovata.
Conclusion: The findings indicate that environmental radon acts as a strong stressor, triggering molecular defense responses in C. ovata. Prolonged exposure of perennial plants to radioactive radiation may induce genetic mutations, alter the structure and function of enzymes in secondary metabolite biosynthetic pathways, and elicit protective responses against free radical damage, likely through stimulation of plant defense pathways during specific radon exposure intervals. Myro and TTG genes play key roles in secondary defense and detoxification pathways, and their increased expression may reflect heightened activity of oxidative stress response systems under specific environmental conditions. Additionally, differences in gene response across elevation ranges may be attributed to actual radon concentrations, environmental factors, absorption rates, and tissue sensitivity. This study provides the first evidence that environmental radon exposure increases the expression of key defense-related genes in C. ovata, with implications for plant adaptation, ecological interactions, and crop quality in radon-contaminated areas. Consequently, environmental radioactive pollutants highlight the need for further research into the molecular mechanisms of plant responses.
Methods: Plant samples were collected from the mountain of Kojanagh village, located 18 km northwest of Meshginshahr (geographical coordinates: 38°29'17.7" N, 47°30'15.1" E). All geographic calculations were performed using a Garmin Oregon 650 GPS device. To obtain comprehensive information on the region’s radiation pollution, a point-by-point radon radiation map was prepared at 10 locations using a Victoreen 451 radiation meter (Fluke Biomedical Company, USA) over two consecutive years. These measurements included points at similar elevations on two adjacent mountains one with radioactive exposure (A) and one without exposure (B). Total RNA was extracted from leaf tissue, and cDNA for myrosinase and TTG genes was synthesized for expression analysis (qRT-PCR). Gene expression levels were normalized to actin as a reference gene. Relative gene expression was calculated using the 2−ΔCt method, with actin as the internal control. Statistical analysis was performed with GraphPad Prism 10 (GraphPad Software, USA). Differences in gene expression between radon-exposed and control samples were evaluated using independent t-tests, with significance set at P<0.05.
Results: Analysis of myrosinase gene expression in C. ovata under varying radon gas levels showed that the highest increase occurred at elevations of 910–920 meters (site A) with an average radiation intensity of 0.8 mSv, where gene expression exceeded seven times that of the non-radioactive control area. At elevations of 930–940 meters (site A) with an average intensity of 1.8 mSv, a roughly fourfold increase was observed compared to the control. In other elevations, gene expression was lower. These findings suggest a nonlinear, elevation-dependent response in myrosinase gene expression, with optimal stimulation at mid-elevations (910–920 meters). The TTG gene expression pattern showed similar changes across elevation ranges, with the highest expression also at 910–920 meters (about fourfold higher than the control). In this range, the standard error was relatively high, indicating variability among samples. A significant increase was also observed at 880–900 meters (about 2.5 times higher than control). At lower (830–860 meters) and higher (950–1000 meters) elevations, expression levels were approximately 1.5 and 1.8 times higher, respectively. The lowest gene expression, like myrosinase, was observed at 880–900 meters. Both Myro and TTG genes exhibited similar expression patterns under different radon exposures, with the highest increase at mid-elevations (910–920 meters, 0.8 mSv average radiation).involved. This study highlights Myro as a potential molecular marker for radon stress in C. ovata.
Conclusion: The findings indicate that environmental radon acts as a strong stressor, triggering molecular defense responses in C. ovata. Prolonged exposure of perennial plants to radioactive radiation may induce genetic mutations, alter the structure and function of enzymes in secondary metabolite biosynthetic pathways, and elicit protective responses against free radical damage, likely through stimulation of plant defense pathways during specific radon exposure intervals. Myro and TTG genes play key roles in secondary defense and detoxification pathways, and their increased expression may reflect heightened activity of oxidative stress response systems under specific environmental conditions. Additionally, differences in gene response across elevation ranges may be attributed to actual radon concentrations, environmental factors, absorption rates, and tissue sensitivity. This study provides the first evidence that environmental radon exposure increases the expression of key defense-related genes in C. ovata, with implications for plant adaptation, ecological interactions, and crop quality in radon-contaminated areas. Consequently, environmental radioactive pollutants highlight the need for further research into the molecular mechanisms of plant responses.
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