Long term effects of ionising radiation in the Chernobyl Exclusion zone on DNA integrity and chemical defence systems of Scots pine (Pinus sylvestris)

Chronic ionizing radiation might suppress resistance to pathogens in aquatic plants without substantial oxidative stress

Chronic ionizing radiation causes elevated levels of DNA damage and reactive oxygen species in plants. Aquatic ecosystems in Chornobyl zone, a major radiological disaster site, are contaminated by harmful radionuclides. We focused on explaining the biochemical mechanisms responsible for the susceptibility of a wild aquatic plant (common reed, Phragmites australis) grown in Chornobyl zone to biotic stress. The fungal infection assay indicated that life in a radionuclide-contaminated environment might compromise plant immunity. Proteome profiling identified 1,867 proteins and we selected several dozen proteins with consistently higher and lower abundance in the samples from the littoral of contaminated lakes by hierarchical clustering. Discordant expression of coding genes pointed to posttranscriptional regulation. Proteins that accumulated in reed upon chronic irradiation suggested a biochemically stable phenotype with effective protection against reactive carbonyls. Simultaneously, proteins that depleted in plants collected from the littoral of radiologically contaminated lakes indicated worse stress resilience and enhanced susceptibility to biotic agents. Furthermore, the quantification of antioxidant enzyme activities and carbonylated proteins rebutted the idea about substantial oxidative stress in chronically irradiated plants. We advocate the necessity to consider increased pathogen sensitivity while developing policies for the management of radionuclide-contaminated areas.

Molecular mechanisms of neutron radiation dose effects on M1 generation peas

The dose effect of radiation has long been a topic of concern, but the molecular mechanism behind it is still unclear. In this study, dried pea seeds were irradiated with 252Cf fission neutron source. Through analyzing the transcriptome and proteome of M1 generation pea (Pisum sativum L.) leaves, we studied the molecular rule and mechanism of neutron dose effect. Our results showed three important rules of global gene expression in the studied dose range. The rule closely related to the neutron absorbed dose at the transcription and translation levels is: the greater the difference in neutron absorbed dose between two radiation treatment groups, the greater the difference in differential expression between the two groups and the control group. We also obtained important sensitive metabolic pathways of neutron radiation, as well as related key genes. Furthermore, the overall molecular regulation mechanism of dose effect was revealed based on the main functional items obtained. Our research results can be applied to appropriate radiation dose estimation and agricultural production practice.

The surface of small glaciers as radioactive hotspots: Concentration of radioisotopes during predicted intensive melting in the Alps

Glaciers are considered secondary sources of pollutants, including radioisotopes such as Cesium or Plutonium, with heightened concentrations compared to other ecosystems. The predicted melting of glaciers poses a substantial risk of releasing stored radioisotopes, yet understanding the glacier-specific factors influencing their concentration remains limited. This study investigates the relationship between glacier altitude, surface area, organic matter content in dark supraglacial sediment (cryoconite), precipitation, and activity concentrations of natural (210Pb) and anthropogenic radionuclides (137Cs and 241Am) across 19 Alpine glaciers. Results indicate that radioisotope concentrations depend on organic matter content in the cryoconite, highlighting the role of biotic-abiotic interactions in pollutant accumulation on glaciers. Moreover, 210Pb activity concentration decreases with glacier altitude, likely due to atmospheric variations in 222Rn. Water precipitation events, such as during peaks in 137Cs deposition and after the Chernobyl Nuclear Power Plant disaster, do not impact current activity concentrations. Importantly, radioisotope concentrations in cryoconite are higher on smaller glaciers. This directly supports the hypothesis that the cryoconite retains a significant share of radioisotopes stored in the ice during intensive melting. Since many small glaciers in the Alps are predicted to disappear within the next 50 years, we anticipate release of radioisotopes to mountain ecosystems might be higher than previously forecasted.

Complexity of responses to ionizing radiation in plants, and the impact on interacting biotic factors

In nature, plants are simultaneously exposed to different abiotic (e.g., heat, drought, and salinity) and biotic (e.g., bacteria, fungi, and insects) stresses. Climate change and anthropogenic pressure are expected to intensify the frequency of stress factors. Although plants are well equipped with unique and common defense systems protecting against stressors, they may compromise their growth and development for survival in such challenging environments. Ionizing radiation is a peculiar stress factor capable of causing clustered damage. Radionuclides are both naturally present on the planet and produced by human activities. Natural and artificial radioactivity affects plants on molecular, biochemical, cellular, physiological, populational, and transgenerational levels. Moreover, the fitness of pests, pathogens, and symbionts is concomitantly challenged in radiologically contaminated areas. Plant responses to artificial acute ionizing radiation exposure and laboratory-simulated or field chronic exposure are often discordant. Acute or chronic ionizing radiation exposure may occasionally prime the defense system of plants to better tolerate the biotic stress or could often exhaust their metabolic reserves, making plants more susceptible to pests and pathogens. Currently, these alternatives are only marginally explored. Our review summarizes the available literature on the responses of host plants, biotic factors, and their interaction to ionizing radiation exposure. Such systematic analysis contributes to improved risk assessment in radiologically contaminated areas.

Changes in Biologically Active Compounds in Pinus sylvestris Needles after Lymantria monacha Outbreaks and Treatment with Foray 76B

Due to climate warming, the occurrence of Lymantria monacha outbreaks is predicted to become more frequent, causing repeated and severe damage to conifer trees. Currently, the most effective way to control the outbreaks is aerial spraying with the bioinsecticide Foray 76B. The present study aimed to determine the impact of both: (i) L. monacha outbreaks and (ii) treatment with Foray 76B on tree resistance through the synthesis of polyphenols (TPC), flavonoids (TFC), photosynthetic pigments (chlorophyll a and b, carotenoids), lipid peroxidation (MDA), and soluble sugars (TSS) in Pinus sylvestris needles. Samples were collected from visually healthy (control), damaged/untreated, and damaged/Foray 76B-treated plots in 2020 and 2021 (following year after the outbreaks). The results revealed that L. monacha outbreaks contributed to the increase in TPC by 34.1% in 2020 and 26.7% in 2021. TFC negatively correlated with TPC, resulting in 17.6% and 11.1% lower concentrations in L. monacha-damaged plots in 2020 and 2021, respectively. A decrease in MDA was found in the damaged plots in both 2020 and 2021 (10.2% and 23.3%, respectively), which was associated with the increased synthesis of photosynthetic pigments in 2021. The research results also showed that in the following year after the outbreaks, the increase in the synthesis of photosynthetic pigments was also affected by the treatment with Foray 76B. Moreover, the increase in the synthesis of TPC and photosynthetic pigments in the damaged plots in 2021 illustrates the ability of pines to keep an activated defense system to fight biotic stress. Meanwhile, a higher synthesis of photosynthetic pigments in Foray 76B-treated plots indicates a possible effect of the treatment on faster tree growth and forest recovery after L. monacha outbreaks.