Agricultural soil degradation is occurring at unprecedented rates, not only as an indirect effect of climate change (CC) but also due to intensified agricultural practices which affect soil properties and biodiversity. Therefore, understanding the impacts of CC and soil degradation on plant physiology is crucial for the sustainable development of mitigation strategies to prevent crop productivity losses. The amino acid proline has long been recognized for playing distinct roles in plant cells undergoing osmotic stress. Due to its osmoprotectant and redox-buffering ability, a positive correlation between proline accumulation and plants’ tolerance to abiotic stress has been pointed out in numerous reviews. Indeed, proline quantification is used systematically by plant physiologists as an indicator of the degree of tolerance and a measurement of the antioxidant potential in plants under stressful conditions. Moreover, the exogenous application of proline has been shown to increase resilience to several stress factors, including those related to soil degradation such as salinity and exposure to metals and xenobiotics. However, recent data from several studies often refer to proline accumulation as a signal of stress sensitivity with no clear correlation with improved antioxidant activity or higher stress tolerance, including when proline is used exogenously as a stress reliever. Nevertheless, endogenous proline levels are strongly modified by these stresses, proving its involvement in plant responses. Hence, one main question arises—is proline augmentation always a sign of improved stress resilience? From this perspective, the present review aims to provide a more comprehensive understanding of the implications of proline accumulation in plants under abiotic stress induced by soil degradation factors, reinforcing the idea that proline quantification should not be employed as a sole indicator of stress sensitivity or resilience but rather complemented with further biochemical and physiological endpoints.
According to the developmental origins of health and disease (DOHaD) hypothesis, changes in the maternal environment are known to reprogram the metabolic response of offspring. Known for its redox modulation, caloric restriction extends the lifespan of some species, which contributes to diminished cellular damage. Little is known about the effects of gestational caloric restriction, in terms of antioxidant parameters and molecular mechanisms of action, on the reproductive organs of offspring. This study assessed the effects of moderate (20%) caloric restriction on redox status parameters, molecular expression of sirtuin (SIRT) 1 and SIRT3 and histopathological markers in the ovaries and testes of adult rats that were subjected to gestational caloric restriction. Although enzyme activity was increased, ovaries from female pups contained high levels of oxidants, whereas testes from male pups had decreased antioxidant enzyme defences, as evidenced by diminished glyoxalase I activity and reduced glutathione content. Expression of SIRT3, a deacetylase enzyme related to cellular bioenergetics, was increased in both ovaries and testes. Previous studies have suggested that, in ovaries, diminished antioxidant metabolism can lead to premature ovarian failure. Unfortunately, there is little information regarding the redox profile in the testis. This study is the first to assess the redox network in both ovaries and testes, suggesting that, although intrauterine caloric restriction improves molecular mechanisms, it has a negative effect on the antioxidant network and redox status of reproductive organs of young adult rats.
While nanomaterials offer wide-ranging solutions, their intensified use causes environmental contamination, posing ecotoxicological risks to several organisms, including plants. It becomes important to understand the phytotoxicity of NMs and find sustainable strategies to enhance plant tolerance to these emerging contaminants. Thus, this study aimed to evaluate the potential of ascorbic acid (AsA) in increasing the tolerance of in vitro grown tomato seedlings to nickel oxide nanomaterials (nano-NiO). Seeds of Solanum lycopersicum cv. Micro-Tom were germinated in culture medium containing 30 mg/L nano-NiO, 150 mg/L AsA, or a combination of both. A control situation was included. Surprisingly, single AsA administration in the medium impaired the growth of tomato seedlings and increased the lipid peroxidation of biomembranes. Nonetheless, plant development was more severely repressed by nano-NiO, with evident macroscopic effects that did not translate into serious redox disorders. Still, proline and AsA levels diminished in response to nano-NiO, while glutathione and phenols increased. Despite the negative effects of AsA on non-stressed plants, nano-NiO-induced stress was counteracted by AsA supply, with enhanced levels of glutathione and phenols. Overall, the supplementation with AsA proved to be a “blessing in disguise” for plants under nano-NiO-induced stress, improving antioxidant capacity and activating other defense mechanisms.
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