Abstract
Allantoin ((AT) a purine metabolite)-mediated ultraviolet C (UVC) stress mitigation has not been studied to date. Here, we reported the physicochemical mechanisms of UVC-induced stress in tomato (Solanum lycopersicum L.) plants, including an AT-directed mitigation strategy. UVC stress reduced plant growth and photosynthetic pigments. Heatmap and principal component analysis (PCA) revealed that these toxic impacts were triggered by the greater oxidative damage and disruption of osmolyte homeostasis. However, pre-treatment of AT noticeably ameliorated the stress-induced toxicity as evident by enhanced chlorophyll, soluble protein, and soluble carbohydrate contents in AT-pretreated UVC-stressed plants relative to only stressed plants leading to the improvement of the plant growth and biomass. Moreover, AT pre-treatment enhanced endogenous AT and allantoate content, phenylalanine ammonia-lyase, non-enzymatic antioxidants, and the enzymatic antioxidants leading to reduced oxidative stress markers compared with only stressed plants, indicating the protective effect of AT against oxidative damage. Moreover, PCA displayed that the protective roles of AT strongly associate with the improved antioxidants. On the other hand, post-treatment of AT showed less efficacy in UVC stress mitigation relative to pre-treatment of AT. Overall, this finding illustrated that AT pre-treatment could be an effective way to counteract the UVC stress in tomato, and perhaps in other crop plants.
Highlights
Plants utilize sunlight as an energy source, which acts as an essential environmental signal to regulate growth and developmental processes via photosynthesis [1]
The phenotypic appearance and values of fresh and dry matter of shoot and root revealed that the ultraviolet C (UVC) stress evoked a visible deleterious effect on tomato plants in a dosedependent manner (Figure S1A and Table S1)
We selected the first UVC irradiance (0.6 W m−2) that caused a significant reduction in the endogenous AT and allantoate contents to be used for applying different doses of exogenous AT
Summary
Plants utilize sunlight as an energy source, which acts as an essential environmental signal to regulate growth and developmental processes via photosynthesis [1]. The most energetic part of the UV spectrum is UVC, which hardly reaches the earth’s biosphere due to its filtration in the stratosphere’s ozone layer, but is used artificially to kill the pathogens [7,8] This nonionizing region of the electromagnetic spectrum regulates the morphological, physiological, and biochemical processes of plants as well as induces plant photomorphogenic development [9]. UV radiation with longer exposure time induced photosynthetic electron transport system inhibition It stimulates the production of excessive reactive oxygen species (ROS), which exceeds the antioxidant capacity of plants leading to membrane lipid and protein oxidation and DNA damage [1,3,15]. Despite the filtration of natural UVC via the ozone layer, it has become a point of concern due to its future impact on natural ecosystems and agricultural productions due to atmospheric pollutant-induced ozone layer depletion [7,17,18]
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