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Acetolactate synthase inhibitors (ALS inhibitors) and glyphosate are two classes of herbicides that act by inhibiting an enzyme in the biosynthetic pathway of branched-chain or aromatic amino acids, respectively. Besides amino acid synthesis inhibition, both herbicides trigger similar physiological effects in plants. The main aim of this study was to evaluate the role of glutathione metabolism, with special emphasis on glutathione S-transferases (GSTs), in the mode of action of glyphosate and ALS inhibitors in Amaranthus palmeri. For that purpose, plants belonging to a glyphosate-sensitive (GLS) and a glyphosate-resistant (GLR) population were treated with different doses of glyphosate, and plants belonging to an ALS-inhibitor sensitive (AIS) and an ALS-inhibitor resistant (AIR) population were treated with different doses of the ALS inhibitor nicosulfuron. Glutathione-related contents, GST activity, and related gene expressions (glutamate-cysteine ligase, glutathione reductase, Phi GST and Tau GST) were analysed in leaves. According to the results of the analytical determinations, there were virtually no basal differences between GLS and GLR plants or between AIS and AIR plants. Glutathione synthesis and turnover did not follow a clear pattern in response to herbicides, but GST activity and gene expression (especially Phi GSTs) increased with both herbicides in treated sensitive plants, possibly related to the rocketing H 2 O 2 accumulation. As GSTs offered the clearest results, these were further investigated with a multiple resistant (MR) population, compressing target-site resistance to both glyphosate and the ALS inhibitor pyrithiobac. As in single-resistant plants, measured parameters in the MR population were unaffected by herbicides, meaning that the increase in GST activity and expression occurs due to herbicide interactions with the target enzymes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Cadmium (Cd) activates the DNA damage response (DDR) and inhibits the cell cycle in Arabidopsis thaliana through the transcription factor SUPPRESSOR OF GAMMA RESPONSE 1. The aim of this study was to investigate which individual leaf best reflects the Cd-induced effects on the regulation of the DDR and cell cycle progression in rosettes, enabling a more profound interpretation of the rosette data since detailed information, provided by the individual leaf responses, is lost when studying the whole rosette. Wild-type A. thaliana plants were cultivated in hydroponics and exposed to different Cd concentrations. Studied individual leaves were leaf 1 and 2, which emerged before Cd exposure, and leaf 3, which emerged upon Cd exposure. The DDR and cell cycle regulation were studied in rosettes as well as individual leaves after several days of Cd exposure. Varying concentration-dependent response patterns were observed between the entire rosette and individual leaves. Gene expression of selected DDR and cell cycle regulators showed higher similarity in their response between the rosette and the individual leaf emerged during Cd exposure than between both individual leaves. The same pattern was observed for plant growth and cell cycle-related parameters. We conclude that Cd-induced effects on the regulation of the DDR and cell cycle progression in the leaf that emerged during Cd exposure, resemble those observed in the rosette the most, which contributes to the interpretation of the rosette data in the framework of plant development and after exposure to Cd., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ann Cuypers has patent #Method for determining a toxicity and/or growth promotion effect of a treatment or compound (EP2022052518W) pending to Hasselt University., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

As sessile organisms, plants have to deal with unfavourable conditions by acclimating or adapting in order to survive. Regulation of flower induction is one such mechanism to ensure reproduction and species survival. Flowering is a tightly regulated process under the control of a network of genes, which can be affected by environmental cues and stress. The effects of ionising radiation (IR) on flowering, however, have been poorly studied. Understanding the effects of ionising radiation on flowering, including the timing, gene pathways, and epigenetics involved, is crucial in the continuing effort of environmental radiation protection. The review shows that plants alter their flowering pattern in response to IR, with various flowering related genes (eg. FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT), CONSTANS (CO), GIGANTEA (GI), APETALA1 (AP1), LEAFY (LFY)) and epigenetic processes (DNA methylation, and miRNA expression eg. miRNA169, miR156, miR172) being affected. Thereby, showing a hypothetical IR-induced flowering mechanism. Further research on the interaction between IR and flowering in plants is, however, needed to elucidate the mechanisms behind the stress-induced flowering response., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Uranium, a heavy metal and primordial radionuclide, is present in surface waters and soils both naturally and due to industrial activities. Uranium is known to be toxic to plants and its uptake and toxicity can be influenced by multiple factors such as pH and the presence of different ions. However, the precise role of the different ions in uranium uptake is not yet known. Here we investigated whether calcium influences uranium uptake and toxicity in the terrestrial plant Arabidopsis thaliana. To this end, A. thaliana plants were exposed to different calcium and uranium concentrations and furthermore, calcium channels were blocked using the calcium channel blocker lanthanum chloride (LaCl 3 ). Fresh weight, relative growth rate, concentration of nutrients and uranium and gene expression of oxidative stress-related genes and calcium transporters were determined in roots and shoots. Calcium affected plant growth and oxidative stress in both control (no uranium) and uranium-exposed plants. In shoots, this was influenced by the total calcium concentration, but not by the different tested uranium concentrations. Uranium in turn did influence calcium uptake and distribution. Uranium-exposed plants grown in a medium with a higher calcium concentration showed an increase in gene expression of NADPH oxidases RBOHC and RBOHE and calcium transporter CAX7 after uranium exposure. In roots, these calcium-dependent responses in gene expression were not observed. This indicates that calcium indeed affects uranium toxicity, but only in shoots. In addition, a clear influence of uranium and LaCl 3 (separately and combined) on the expression of calcium transporters was observed., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Glutathione (GSH) is an important player in plant responses to cadmium (Cd) through its dual function as an antioxidant and precursor for metal-chelating phytochelatins (PCs). In addition, it was shown to be involved in cell cycle regulation in Arabidopsis thaliana roots, but its involvement in this process in leaves is largely unknown and has never been evaluated in Cd-exposed plants. This study aimed to elucidate the role of GSH in leaf growth and development, metal chelation, nutrient homeostasis and cell cycle regulation in A. thaliana plants upon prolonged Cd exposure. Responses were compared between wild-type (WT) plants and three GSH-deficient mutants. Our results indicate that PC production remains important in plants exposed to Cd for an extended duration. Furthermore, an important role for GSH in regulating nutrient homeostasis in Cd-exposed plants was revealed. Cell cycle analysis demonstrated that negative effects of Cd exposure on cell division and endoreplication were more pronounced in leaves of the GSH-deficient cadmium-sensitive 2-1 (cad2-1) mutant in comparison to the WT, indicating the involvement of GSH in cell cycle regulation. Finally, a crucial role for GSH in transcriptional activation of the Cd-induced DNA damage response (DDR) was revealed, as the Cd-induced upregulation of DDR-related genes was either less pronounced or completely abolished in leaves of the GSH-deficient mutants., (Copyright © 2020. Published by Elsevier Masson SAS.)

This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mechanisms of cadmium (Cd)-induced detoxification (i.e. chelation and antioxidative defence). A kinetic study was conducted on hydroponically grown Arabidopsis thaliana (L. Heyhn) to gain insight into the early events after exposure to Cd. Cadmium detoxification was investigated at different levels, including gene transcripts, enzyme activities and metabolite content. Data indicate a time-dependent response both within roots and between plant organs. Early on in roots, GSH was preferentially allocated to phytochelatin (PC) synthesis destined for Cd chelation. This led to decreased GSH levels, without alternative pathways activated to complement GSH's antioxidative functions. After one day however, multiple antioxidative pathways increased including superoxide dismutase (SOD), ascorbate (AsA) and catalase (CAT) to ensure efficient neutralization of Cd-induced reactive oxygen species (ROS). As a consequence of Cd retention and detoxification in roots, a delayed response occurred in leaves. Together with high leaf thiol contents and possibly signalling responses from the roots, the leaves were protected, allowing them sufficient time to activate their defence mechanisms., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

To study the impact of environmental uranium (U) contamination, effects should be analysed at different environmentally relevant pH levels as the speciation of U, and hence its toxicity, is strongly dependent on the pH. As photosynthesis is a major energy producing process in plants intimately connected to plant growth and known to be susceptible to metal stress, the effects of different U concentrations on photosynthesis in 18-day-old Arabidopsis thaliana (Columbia ecotype) are investigated at two contrasting pH levels, pH 4.5 and pH 7.5. At pH 4.5, U is highly taken up by the roots but is poorly translocated to the shoots, while at pH 7.5, less U is taken up but the translocation is higher. The lower U concentrations in the shoots at pH 4.5 are accompanied by a more reduced leaf growth as compared to pH 7.5. In addition, U does not influence the photosynthetic machinery at pH 7.5, while an optimization of the photosynthesis takes place after U exposure at pH 4.5. As such, more of the absorbed quanta are effectively used for photosynthesis accompanied by a decreased non-photochemical quenching and an increased electron transport rate. Since the enhanced photosynthesis at pH 4.5 is accompanied by a decreased growth, we suggest that the energy produced during photosynthesis is used for defence reactions against U-induced oxidative stress rather than for growth. As such, a high discrepancy was observed between the two pH levels, with an optimized photosynthetic apparatus at pH 4.5 and almost no effects at pH 7.5., (Copyright © 2014. Published by Elsevier Masson SAS.)

Lipoxygenases (LOXes, EC 1.13.11.12) are involved in growth, development and responses to stress. Earlier results suggested a role in stress generation, signalling and/or responses when Arabidopsis thaliana is exposed to cadmium (Cd), and expression of the cytosolic LOX1 was highly upregulated in the roots after Cd exposure. To investigate the involvement of LOX1 in early metal stress responses, three-week-old wild-type and lox1-1 mutant A. thaliana plants were acutely (24 h) exposed to realistic Cd concentrations (5 and 10 μM) and several oxidative stress and signalling related parameters were studied at transcriptional and biochemical levels. Transcription of several genes encoding ROS producing and scavenging enzymes failed to be induced up to wild-type levels after Cd exposure. Expression of 9-LOX enzymes was inhibited in lox1-1 mutant roots due to lack of functional LOX1 and downregulated LOX5 expression, and the lox1-1 mutation also interfered with the expression of genes involved in jasmonate biosynthesis. LOX1 and RBOHD may be involved in stress signalling from roots to shoots, as the induction of APX2 expression, which is dependent on RBOHD activity, was disrupted in lox1-1 while RBOHD failed to be upregulated. A different pattern of H(2)O(2) production and ascorbate and glutathione levels in lox1-1 mutants after Cd exposure may have indirectly influenced gene expression patterns. Although indirect effects of the lox1-1 mutation on gene expression complicate the determination of exact sensing - signalling - response pathways, the results presented here outline a more refined LOX1 functioning in Cd-induced stress responses that could be used in studies determining the exact involvement of LOX1 in these pathways., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

To improve the knowledge about the use of plants for the removal of toxic metals from contaminated soils, metabolic and transcriptional responses of Brassica carinata to different forms of copper (Cu) were studied. Two-week-old hydroponically grown seedlings were exposed for 24 h to 30 μM CuSO₄ or CuEDDS. CuSO₄ appeared to be more toxic than CuEDDS as roots showed higher levels of thiobarbituric acid reactive substances (TBARS) and increased relative leakage ratios (RLR), although the superoxide dismutase (SOD, EC 1.15.1.1) activity increased following both exposures. In CuSO₄-exposed seedlings the higher toxicity was underlined by increased transcription of lipoxygenases (EC 1.13.11.12) and NADPH oxidases (EC 1.6.99.6) and by the higher Cu accumulation in both tissues compared to CuEDDS exposure. The presence of EDDS increased Cu translocation, which resulted 5-times higher than when exposed to CuSO₄. Decreases in catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) activities together with increases of reduced glutathione (GSH) and tocopherols and a reduction of lipoic acid (LA) were observed in roots of CuSO₄-exposed seedlings. On the contrary, CuEDDS exposure induced a general increase in enzyme activities and decreases in ascorbate (AsA) and tocopherol levels. In the primary leaves, in both exposures Cu differently affected the oxidative stress responses indicating that the cellular redox balance was anyway maintained. EDDS plays a crucial role in B. carinata tolerance to oxidative stress induced by Cu and might be proposed to improve the efficiency of Cu phytoextraction., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Plants exposed to cadmium (Cd) show morphological and physiological disorders. To increase our knowledge regarding Cd-induced signalling, most often the effects of acute exposure are investigated. However, this does not allow in-depth analysis of morphological effects. Therefore, we chronically exposed Arabidopsis thaliana plants to environmentally realistic Cd concentrations (5 or 10 μM) and, using a described phenotypic framework methodology, we determined the impact of Cd on the plant's ability to complete its life cycle and produce germinative seeds. Visible Cd-induced morphological changes were observed within a short exposure period, with chlorotic and anthocyanous leaf colouring occurring dose-dependently. Although rosette growth was severely reduced in Cd-exposed plants, all plants were able to emerge inflorescences and produce siliques containing germinative seeds, thus confirming the non-lethality of the used Cd concentrations. Although the growth inhibition of Cd-exposed plants was dependent on the dose, both concentrations had similar effects on inflorescence height and silique counts. In conclusion, vegetative growth of plants chronically exposed to Cd is inhibited in a concentration-dependent manner. However, the effect on plant regeneration is clearly stress-determined but independent on the Cd concentration applied. In Arabidopsis thaliana, vegetative and reproductive growth are differentially influenced by Cd., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

Erica andevalensis is an endemic species from SW Iberian Peninsula, always growing in metal-enriched and acid soils. In the present study, a comparison was made between wild E. andevalensis plants collected from the field and cultivated ones exposed to different cadmium levels (0, 0.5, 5 and 50 μM). Wild plants contain higher levels of ascorbic acid (around 8000 nmol g(-1) FW) than lab-cultivated control plants (around 3000 nmol g(-1) FW). Glutathione levels follow an opposite trend being smaller in wild plants than lab-cultivated ones. Moreover, the total antioxidant capacity of wild plants is 90 times higher than in cultivated plants non-exposed to cadmium. Cadmium treatment of lab-cultivated plants did not affect the growth of E. andevalensis or the glutathione levels. However, the total antioxidative capacity increased in plants exposed to 50 μM of cadmium. Cadmium was added to the soil and it was transported into leaves reaching levels of 3.299 ± 0.781 μg Cd/g DW in plants exposed to 50 μM. These results underline a possible importance of antioxidants in the metal tolerance show by the high antioxidant capacity detected in both wild and lab-cultivated plants exposed to high cadmium levels., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

In this study, toxicity effects in plants of uranium in a binary pollution condition were investigated by studying biological responses and unraveling oxidative stress related mechanisms in Arabidopsis thaliana seedlings, grown on hydroponics and exposed for 3 days to 10 μM uranium in combination with 5 μM cadmium. While uranium mostly accumulated in the roots with very low root-to-shoot transport, cadmium was taken up less by the roots but showed higher translocation to the shoots. Under mixed exposure, cadmium influenced uranium uptake highly but not the other way round resulting in a doubled uranium concentration in the roots. Under our mixed exposure conditions, it is clear that micronutrient concentrations in the roots are strongly influenced by addition of cadmium as a second stressor, while leaf macronutrient concentrations are mostly influenced by uranium. Oxidative stress related responses are highly affected by cadmium while uranium influence is more limited. Hereby, an important role was attributed to the ascorbate redox balance together with glutathione as both metabolites, but more explicitly for ascorbate, increased their reduced form, indicating an important defense and regulatory function. While for roots, based on an increase in FSD1 gene expression, oxidative stress was suggested to be superoxide induced, in leaves on the other hand, hydrogen peroxide related genes were mostly altered., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Arabidopsis thaliana was exposed to low-dose chronic gamma irradiation during a full life cycle (seed to seed) and several biological responses were investigated. Applied dose rates were 2336, 367 and 81 microGy h(-1). Following 24 days (inflorescence emergence), 34 days (approximately 50% of flowers open) and 54 days (silice ripening) exposure, plants were harvested and monitored for biometric parameters, capacities of enzymes involved in the antioxidative defence mechanisms (SOD, APOD, GLUR, GPOD, SPOD, CAT, ME), glutathione and ascorbate pool, lipid peroxidation products, altered gene expression of selected genes encoding for antioxidative enzymes or reactive oxygen species production, and DNA integrity. Root fresh weight was significantly reduced after gamma exposure compared to the control at all stages monitored but no significant differences in root weight for the different dose rates applied was observed. Leaf and stem fresh weight were significantly reduced at the highest irradiation level after 54 days exposure only. Also total plant fresh was significantly lower at silice riping and this for the highest and medium dose rate applied. The dose rate estimated to result in a 10% reduction in growth (EDR-10) ranged between 60 and 80 microGy h(-1). Germination of seeds from the gamma irradiated plants was not hampered. For several of the antioxidative defence enzymes studied, the enzyme capacity was generally stimulated towards flowering but generally no significant effect of dose rate on enzyme capacity was observed. Gene analysis revealed a significant transient and dose dependent change in expression of RBOHC indicating active reactive oxygen production induced by gamma irradiation. No effect of irradiation was observed on concentration or reduction state of the non-enzymatic antioxidants, ascorbate and glutathione. The level of lipid peroxidation products remained constant throughout the observation period and was not affected by dose rate. The comet assay did not reveal any effect of gamma dose rate on DNA integrity., (2010 Elsevier Masson SAS. All rights reserved.)

The production of reactive oxygen species (ROS) and the induction of the antioxidative defense mechanism are very important in heavy metal toxicity. In this study, biological effects induced after uranium contamination were investigated for Arabidopsis thaliana. Three-week-old seedlings were exposed for 4days to 100microM U in an adjusted Hoagland solution. Uranium exposure caused a decreased growth of leaves (38%) and roots (70%) and a modified nutrient profile was observed. Investigation of lipid peroxidation products indicated a significant increase of membrane damage. Important ROS-producing and -scavenging enzymes were studied at transcriptional and protein level to investigate the importance of the ROS-signature in uranium toxicity. Elevated gene expression was observed for NADPH-oxidase, a ROS-producing enzyme. Changes in gene expression for different ROS-scavenging enzymes as Cu/ZnSOD, FeSOD and APX were also observed. Analysis of enzyme capacities showed little effects after uranium contamination. Higher ascorbate levels in uranium exposed leaves suggested an increase of antioxidative defense via the ascorbate-glutathione pathway after uranium exposure. Theoretical calculations indicated rapid formation of uranium-phosphate precipitates if normal phosphate concentrations are used. Precipitation tests recommend the use of 25microM P in combination with 100microM U to inhibit uranium precipitation. Because this combination was used for uranium toxicity investigation, the influence of this low phosphate concentration on plant growth and oxidative stress had to be evaluated. Minor differences between low phosphate (25microM P) and high phosphate (100microM P) treatments were observed justifying the use of the low phosphate concentration in combination with uranium.

Arabidopsis thaliana is one of the most widely used model organisms in plant sciences. Because of the increasing knowledge in the understanding of its molecular pathways, a reproducible and stable growth set-up for obtaining uniform plants becomes more important. In order to be able to easily harvest and study both roots and shoots, and to allow simple exposure to water-soluble toxic substances, a hydroponic system is the desired cultivation method for controlled plant growth. Based on earlier developed hydroponic cultivation protocols, a hydroponic set-up was optimized and statistically validated using linear mixed-effects models. In order to determine important components that influence the level of variability in a hydroponic set-up, stress-related indicators were examined at the biochemical as well as at the molecular level. It is highly recommended that statistical as well as biological assumptions are carried out before post-analyses are performed. Therefore, we suggest a model where factors that influence variability such as the usage of different pots and harvesting on different times are taken into account in the analyses. Furthermore, in contrast to what has been reported in earlier studies, our findings indicate that continuous aeration of the hydroponic solution is highly important.

Oxidative stress has been shown to be of great importance in the toxicity of several metals (copper, zinc, ...). In this study, the relationship of cadmium phytotoxicity and antioxidative reactions in bean (Phaseolus vulgaris L.) plants was investigated. Eleven-day-old seedlings were exposed to an environmentally realistic concentration of cadmium (2 microM CdSO(4)). Several biochemical and physiological parameters were influenced even by these low concentrations. At the biochemical level, the antioxidative defence mechanism was significantly activated after 24 h of cadmium exposure. Some enzymes able of quenching reactive oxygen species (syringaldazine peroxidase, EC 1.11.1.7; guaiacol peroxidase, EC 1.11.1.7) as well as enzymes important in the reduction of NAD(P)(+) (isocitrate dehydrogenase, EC 1.1.1.42; malic enzyme, EC 1.1.1.40) were significantly elevated by cadmium exposure. Furthermore, the ascorbate-glutathione cycle appeared to be a very important mechanism against cadmium-induced oxidative stress. In leaves, significant increases of ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) and significant changes in the ascorbate and glutathione pool were observed. Morphological and other biochemical parameters (lipid peroxidation) were significantly enhanced 48 h after the start of the cadmium exposure. At the end of the experiment (72 h after the start of the metal treatment), even visual effects, such as chlorosis, were observed. The present data indicate that cadmium, like other metals, induces cellular redox disequilibrium suggesting that an environmentally realistic concentration of cadmium can cause oxidative stress.