Abstract
Excess selenium (Se) causes toxicity, and nitric oxide (NO)’s function in spermine (Spm)-induced tolerance to Se stress is unknown. Using wheat plants exposed to 1 mM sodium selenate—alone or in combination with either 1 mM Spm, 0.1 mM NO donor sodium nitroprusside (SNP) or 0.1 mM NO scavenger cPTIO—the potential beneficial effects of these compounds to palliate Se-induced stress were evaluated at physiological, biochemical and molecular levels. Se-treated plants accumulated Se in their roots (92%) and leaves (95%) more than control plants. Furthermore, Se diminished plant growth, photosynthetic traits and the relative water content and increased the levels of malondialdehyde, H2O2, osmolyte and endogenous NO. Exogenous Spm significantly decreased the levels of malondialdehyde by 28%, H2O2 by 37% and electrolyte leakage by 42%. Combined Spm/NO treatment reduced the Se content and triggered plant growth, photosynthetic traits, antioxidant enzymes and glyoxalase systems. Spm/NO also upregulated MTP1, MTPC3 and HSP70 and downregulated TaPCS1 and NRAMP1 (metal stress-related genes involved in selenium uptake, translocation and detoxification). However, the positive effects of Spm on Se-stressed plants were eliminated by the NO scavenger. Accordingly, data support the notion that Spm palliates selenium-induced oxidative stress since the induced NO elicits antioxidant defence upregulation but downregulates Se uptake and translocation. These findings pave the way for potential biotechnological approaches to supporting sustainable wheat crop production in selenium-contaminated areas.
Highlights
Wheat is the third most important cultivated cereal crop in the world [1] and it is a great source of plant-based protein among the cereals [2]
The current study concludes that excessive Se is a phytotoxic agent and proposes that Spm could represent an effective chemical for mitigating the detrimental impacts of increased Se in wheat by influencing many physiological, biochemical and molecular processes
Spm and nitric oxide (NO) donors play a key role in the alleviation of Se toxicity in wheat plants by modulating antioxidant activities, glyoxalase systems and MG intermediates
Summary
Wheat is the third most important cultivated cereal crop in the world [1] and it is a great source of plant-based protein among the cereals [2]. Antioxidants 2021, 10, 1835 agricultural lands have excess metalloids, which present an emerging threat of great concern because of their overaccumulation in soil, long persistence in the environment and relative toxicity in all living organisms [3,4]. Selenium (Se) is a naturally occurring metalloid, and its phytotoxicity in plants depends on the dose, speciation and target species [5]. The two major forms of Se in soils are selenite and selenate, which are taken up by the roots of plants. Sodium selenate (Na2 SeO4 ) is transported by phosphate transporters in plants and is phytotoxic at high concentrations [6]. The potential of plants to absorb Se in their tissues is proportional to whether they are non-accumulators (1.0 g kg−1 DW) [8]
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